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What is the biological age of grafted plants?

What is the biological age of grafted plants?


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Suppose you graft a piece of an existing 'old' plant onto a host plant. Will the graft continue to grow having the same biological age as its parent? In other words, would the graft die at the same time as its parent plant? Or would the process of grafting result in some sort of rejuvenation of the grafted daughter plant? Or alternatively, would the host plant carrying the graft determine the biological age of the graft primarily?

PS: Personal experience-based (anecdotal) answers are more than welcomed


In my experience (in common with the experience of everyone I've talked to who could be considered an expert on the subject), taking old wood and using that as a scion when grafting new trees rejuvenates them, and they grow as new trees.

I'll take apple trees as an example. As you can see from the table here, there is a distinct age after which the tree begins to decline. Now, that's not concrete (I've seen some apple trees last over 100 years (didn't plant those myself btw)), but generally, an apple tree will lose vigor and productivity before it reaches 50 years of age. This tree's 'immune system' also goes down, and it becomes susceptible to many diseases. You'll rarely see such a tree, as orchardists generally replace them rather fast.

But to the point of your question. When you will graft an apple tree, you will generally bud graft it, as described here. That article (which is spot-on) says:

Select a healthy branch of this year's growth from your desired variety of tree. Look for a plump leaf bud about halfway down the branch. Leaf buds are close to the branch where fruiting buds tend to stand out more.

Note that it says nothing about the tree's age, simply stating that the wood must be healthy. That's because old wood/young wood produce the same result in the new trees. I was using a 40 year old razor russet to graft onto all the Malling V rootstocks I had for that variety. And of course they grew as expected, as a young sapling should. I've heard of a nearby nursery taking budwood from a 100 year old tree that still looked good.

Additionally, you can use a rootstock taken from an old plant, and also a scion from an old plant, and the new plant created will grow as a young sapling. Here's how the rootstocks I use are created: You cut down a tree at ground level, and it sends out a lot of shoots. You pile soil over it, but allow the ends of the shoots to stick through. These shoots will root into the soil, and can be cut at the base, and planted out for grafting later. This way, you can have 1000's of identical (cloned) rootstocks. You can also get rootstocks from old trees. Here's a diagram of the process.


About herbaceous perennials, I've found (to some people's surprise) the same thing. The scion grows as a young plant again once grafted. I found this out because I graft heirloom tomatoes onto hybrid tomato rootstocks (the latter are seedlings). Usually, the scions will be from seedlings, but at times I take the scions from a large mature plant.

Just so you know, an indeterminate tomato plant will, once mature, flower and fruit until frost. A determinate tomato variety will produce a large crop all at once, and then die back (this is the kind preferred by owners of mechanised (machine harvested) fields).

In my tests, you could take the scion from an old determinate plant that was through fruiting, right before it started dying back, and successfully use that for grafting the new plants. These new plants' growth was identical to the growth of grafted plants whose scions came from seedlings, and they began to flower and produce fruit at the same time. Of course, actual seedlings did not have the vigor of the grafted plants, and were behind in growth.

Off-topic for your question, but possibly still of interest, I've found that cuttings and layers (not scions) taken from old plants (both woody and herbaceous), and rooted, would grow as young plants again.


The Living world MCQ Biology Questions

  • The first letter of the genus should be in capital, and all letters in species should be in small letters.
  • If handwritten, there should be a separate underlined for both genus and species.
  • If written digitally, it should be in italics

10. Why we need to classify organisms:

  • a. Because studying each organism is cumbersome as the number of organisms is vast.
  • b. Because classification makes them easy to relate.
  • c. It is easy to find useful trends and evolution trends when we classify them.
  • d. All.

11. Hierarchy of taxonomic classification is:

  • a. Species » Genus » Family » Order.
  • b. Species » Genus » Order » Family.
  • c. Species » Order » Family » Genus.
  • d. None.

12. A species is a group of similar organisms which can:

  • a. Interbreed.
  • b. Interbreed and produce viable offsprings.
  • c. Both.
  • d. None.

13. Can we categorize humans into sub-species?

A herbarium is a collection of specimens.

14. A herbarium is a collection of organism sample:

  • a. In a museum.
  • b. In dried form in files for the record purpose.
  • c. In the garden as living.
  • d. None.

15. The biggest herbarium of India is at:

  • a. The herbarium of Forest Research Institute, Dehradoon.
  • b. Indian Botanical garden, Kolkata.
  • c. None.

16. Biggest herbarium of the world is at:

  • a. India.
  • b. The United States.
  • c. United kingdom.
  • c. France.

17. The largest botanical garden of India is located at:

  • a. Forest Research Institute, Dehradoon.
  • b. Indian Botanical garden, Kolkata.
  • c. None.

1.d 7.a 13. b
2. b 8. b 14. b
3. a 9. c 15. b
4. d 10. d 16. c
5. a 11. a 17. b
6. a 12. b

The Living world MCQ questions/ Objective questions with answers Class 11 chapter 1


New Research Areas

The rise of epigenetics (a complex field of study that examines specific changes in gene activity) and the identification of biological age have been regarded by some as the holy grail in understanding how we grow older. &ldquoPreviously we assumed that the genome, our entire DNA library, didn&rsquot change throughout a person&rsquos life. That&rsquos been proven wrong &mdash it can be modified by the environment,&rdquo says Elaine Chin, M.D., founder and chief medical officer at Executive Health Centre and author of Lifelines: Unlock the Secrets of Your Telomeres for a Longer, Healthier Life.

Scientists have now identified biomarkers (chemical changes) in an individual&rsquos DNA that correspond with aging. These changes can help predict how well you&rsquore going to age, how long you&rsquore going to live, and even if you&rsquore at increased risk for chronic disease.


REACTIVE OXYGEN SPECIES: Metabolism, Oxidative Stress, and Signal Transduction

Klaus Apel and Heribert Hirt
Vol. 55, 2004

Abstract

▪ Abstract Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and . Read More

Figure 1: Generation of different ROS by energy transfer or sequential univalent reduction of ground state triplet oxygen.

Figure 2: The principal features of photosynthetic electron transport under high light stress that lead to the production of ROS in chloroplasts and peroxisomes. Two electron sinks can be used to alle.

Figure 3: The principal modes of enzymatic ROS scavenging by superoxide dismutase (SOD), catalase (CAT), the ascorbate-glutathione cycle, and the glutathione peroxidase (GPX) cycle. SOD converts hydro.

Figure 4: Schematic depiction of cellular ROS sensing and signaling mechanisms. ROS sensors such as membrane-localized histidine kinases can sense extracellular and intracellular ROS. Intracellular RO.

Figure 5: Different roles of ROS under conditions of (a) pathogen attack or (b) abiotic stress. Upon pathogen attack, receptor-induced signaling activates plasma membrane or apoplast-localized oxidase.


Cloning in Plants and Animals

Clones – genes, cells or whole organisms that carry identical genetic material because they are derived from the same original DNA.

Reproductive cloning generates genetically identical organisms.

Non-reproductive cloning generates cells, tissues and organs – can replace those damaged by diseases or accidents.

The advantages of using cloned cells include:

  • Cells won’t be rejected as they’re genetically identical to an individual’s own cells.
  • Prevent waiting fordonor organs to become available for transplant.
  • Cloned cells can be used to generate any cell type because they are totipotent. Damage caused by some diseases and accidents cannot currently be repaired by transplantation or other treatments.
  • Using cloned cells is less likely to be dangerous than a major operation such as a heart transplant.

There are many possibilities for non-reproductive cloning, including:

  • The regeneration of heart muscle cells following a heart attack.
  • The repair of the nervous tissue destroyed by diseases such as multiple sclerosis.
  • Repairing the spinal cord of those paralysed by an accident that results in a broken back or neck.

These techniques are often referred to as therapeutic cloning. However, there are some ethical issues concerning whether cloning should be used in humans. There are ethical objections to the use of human embryonic material and some scientific concerns about a lack of understanding of how cloned cells will behave over time.

  • describe the production of natural clones and in plants using the example of vegetative propagation in elm trees

Natural Vegetative Propagation:

Vegetative propagation is form of asexual reproduction of a plant. Only one plant is involved and the offspring is the result of one parent. The new plant is genetically identical to the parent.

  1. Runners – stems that grow horizontally above the ground. They have nodes where buds are formed, which grow into a new plant, e.g. strawberries and spider plant.
  2. Tubers – new plants will grow out of swollen modified roots called tubers. Buds develop at the base of the stem and then grow into new plants, e.g. potato and daliahs.
  3. Bulbs – a bulb contains an underground stem, with leaves containing stored food At the centre of the bulb is an apical bud, which produces leaves and flowers. Also attached are lateral buds, which produces new shoots, e.g. daffodils.
  4. Basal sprouts (root suckers) – the suckers grow from meristem tissue in the trunk close to the ground, where least damage is likely to have occurred, e.g. elm trees and mint. Root suckers help the elm spread, because they can grow all around the original trunk. When the trunk dies, the suckers grow into a circle of new elms called a clonal patch. This, in turn, puts out new suckers so that the patch keeps expanding as far as resources permit.

Artificial Vegetative Propagation:

  • Taking Cuttings – e.g. geraniums, a section of the stem is cut between leaf joints (nodes). The cut end of the stem is then often treated with plant hormones to encourage root growth, and planted. The cutting forms a new plant, which is a clone of the original parent plant.
  • Grafting – e.g. fruit tree or rosebush, a rootstock is cut to match the wedge-shaped stem to be grafted. The vascular tissue is lined up then binding is wrapped aroundthe graft area to hold it in place until growth supports the grafted section. The graft grows and is genetically identical to the parent plant, but the rootstock is genetically different.
  • Using Tissue Culture – used in order to generate huge numbers of genetically identical plants successfully from a very small amount of plant material. The most common method used in the large-scale cloning of plants is micropropagation, e.g. orchids.

Totipotent – stem cells capable of differentiating into any type of adult cell found in the organism.

In animals, only embryonic cells are naturally capable of going through the stages of development in order to generate a new individual. These cells are totipotent stem cells and they are capable of differentiating into any type of adult cell found in the organism. There are two methods of artificially cloning animals:

Method 1: Splitting Embryos

Cells from a developing embryo can be separated out, with each one then going on to produce a separate, genetically identical organism.

  1. Collect eggs from a high-value female (e.g. high milk yield in cows) and collect sperm from a high-value male.
  2. In vitro fertilisation occurs between the eggs and the sperm.
  3. Grow the in vitro to a 16-cell embryo.
  4. Split the embryo into several separate segments and implant into surrogate mothers.
  5. Each calf produced is a clone.

Method 2: Nuclear Transfer

A differentiated cell from an adult can be taken, and its nucleus placed in an egg cell which has had its own nucleus removed (enucleated cell). The egg then goes through the stages of development using genetic information from the inserted nucleus. The first animal cloned by this method was Dolly the sheep in 1996, which was successful after 277 attempts.


Calculating Your Biological Age

We all know that one person who is running marathons well into their sixties. Which, anecdotally, helps us believe in the optimistic adage that age is just a number. And that the age we feel matters far more than what’s printed on our driver’s license.

But what if there was a number that could tell you the status of your aging from a biological standpoint? Morgan Levine, PhD, an assistant professor in the Department of Pathology at Yale who studies aging, has developed just that: an algorithm that uses a DNA sample to calculate what she calls biological age. We had her break down how the test works, the implications of biological age, and what lifestyle factors can affect it. You can also watch Levine measure the biological age of some lucky goop staffers on our Netflix show, The goop Lab, on January 24.

A Q&A with Morgan Levine, PhD

We think of chronological age as the amount of time since you were born—whatever your driver’s license says—whereas biological age is the age your body resembles or functions at. Even though two people may both be thirty years old chronologically, one of them could have a biological profile that is closer to twenty-five, whereas the other might have a biological profile of thirty-five. The oldest biological age we’ve seen in our lab is around 120 years old.

To calculate biological age, we use epigenetic data, specifically DNA methylation, from a blood sample or another source (more on that in a minute). DNA methylation is basically a chemical modification to your DNA—it doesn’t change the sequence of your DNA, but it does regulate which genes get turned on and which get turned off. And there are specific areas of the genome where there’s increased methylation with age and other areas where there’s decreased methylation with age.

We see very specific patterns of DNA methylation when we look across the entire genome and how it changes with age: We look at those patterns and predict what someone’s biological age is based on hundreds of thousands of these sites that are a reflection of your overall health and functioning.

Companies that offer at-home testing measure biological age in saliva as an indicator of a person’s overall biological age while most scientific studies use blood for this measure. Your biological age in your blood is often similar to that in your saliva because they have many of the same cell types. The exciting thing about using DNA methylation to measure biological age, though, is that we can calculate different biological ages for different parts of the body. This allows for a more nuanced understanding of a person’s biological age across different organs to give a more comprehensive understanding of their overall health and aging. We can take a blood sample from someone and find the biological age of their blood. And then take a skin sample or a saliva sample or a cheek swab and get a different biological age based on those cells. Right now, we’re not taking biopsies from different organs, but you could have a different biological age for your heart than you might have for your liver or even your brain, and that might have more implications for the future health of these specific organs.

We use ten clinical measures that capture health and functioning in multiple systems (immune, metabolic, cardiovascular, kidney, and liver). The clinical biomarkers include c-reactive protein (CRP), total cholesterol, albumin, creatinine, hba1c (your average blood sugar), alkaline phosphatase, and urea nitrogen. We have developed algorithms for combining these to produce estimates of biological age that have been shown to be better indicators of disease and mortality risk than chronological age. The epigenetic test I previously mentioned was developed to mimic the clinical test, so they are extremely similar. The advantage of the epigenetic test is that it doesn’t require blood it can be done using almost any cell or tissue type. They both robustly relate to current and future health.

What we’ve seen so far in our lab is that biological age is associated with a risk of developing different diseases and even early mortality. There’s pretty good evidence that aging is the number one risk factor for most of the diseases that people suffer from: Alzheimer’s disease, heart disease, diabetes, and cancer. If we can see not just someone’s chronological age but also their biological age, we think that this holds more insight into their future risk of developing diseases overall or organ-specific diseases.

“If we can see not just someone’s chronological age but also their biological age, we think that this holds more insight into their future risk of developing diseases overall or organ-specific diseases.”

In our lab, we have samples from individuals’ brains where we have found that biological age is associated with Alzheimer’s disease and samples from the liver that are associated with fatty liver disease. We have a project right now where we have taken breast tissue samples from women who have a history of cancer and women who don’t. We can see that the women who have had breast cancer have older biological ages in their breast tissue than the women who haven’t. None of these samples are from the actual cancer cells they’re from the normal breast tissue itself. This has helped our lab better understand the factors that impact biological age.

We haven’t done clinical trials trying to change biological age, but we can look at people who tend to have younger biological ages than other people their age to draw conclusions. In general, it’s all the things you would think: not smoking, not drinking heavily, eating a lot more plant-based food, exercising regularly, having a higher socioeconomic status, having lower stress, and not having disturbed sleep.

So far, the outcomes associated with biological age seems to be consistent across different demographic groups. However, average biological age does differ by race and ethnicity in a manner consistent with differences in median life expectancy. We don’t think these are inherent differences rather, we think they are due to socioeconomic factors that underlie most health disparities.

We do see that women on average are a little younger biologically than men. This fits pretty well with life expectancy because on average women live longer than men. This is an evolutionarily conserved phenomenon that we even see in animals. People have speculated that it might have to do with having an additional X chromosome or estrogen, but right now that’s an open-ended question in science.

“In women, menopause is associated with accelerating biological age”

One interesting thing we’ve found is that in women, menopause is associated with accelerating biological age to some extent. And there are other periods in life that also have different rates of biological age. It might be counterintuitive, but in early life, during fetal development or childhood, you get the biggest acceleration in biological age. It starts to slow down at maturation, around age fifteen or twenty, and then it begins to increase at a very constant rate. In the later stages of life, even though we don’t have much data, there are some hints that biological age decelerates. So even though individuals are much older, they seem to be aging at a slower rate after around age eighty or ninety.

I work with a company called Elysium that launched an at-home test a few months ago where all you need is a saliva sample and you can get your biological age. It’s similar to a genetic testing kit, but the biggest difference is your genetics are pretty set in stone. You should have to take a genetic test only once, and there’s not much you can do about it. Whereas epigenetics are modifiable. With epigenetics, we can see not just your predisposition based on genetics but also how you’re responding to things. Your body changes based on all of your experiences and all your health habits throughout your whole life.

Right now, the recommendations based on biological age are pretty straightforward: Get enough sleep and eat fruits and vegetables. But in the future, people will be able to use this information to track their habits. You could use the test to make decisions about health behaviors, and the results of these behaviors would be reflected in the test. For example, it’s sometimes unclear how much exercise you should be getting or if you should you do more high-intensity interval training (HIIT) or running workouts. You could take this test and then adjust your lifestyle to see whether there’s any improvement when you take the test again. Having this feedback would give people insight into their own biology, and the more people that eventually do this, the better we will be able to track and learn from the results to hopefully predict what might work best for one person versus another.

Another exciting part of this field is mimetics. Mimetics is the idea that different behaviors (like regular exercise) may have beneficial effects on longevity. And if we can figure out biologically what those things are doing and why they’re beneficial, then maybe we can develop therapeutics that mimic that response. This way, if you’re, say, a person who has a disability and can’t regularly exercise, we could develop ways to tap into those same biological pathways that exercise activates and create that same beneficial effect with a medication or another method.

The longevity and aging field is still fairly new, so we don’t know specifically what things are the most ideal, and these things may also differ from person to person. In animals, we know that things like caloric restriction, fasting, certain drugs, and genetic manipulations can increase longevity.

What I do is eat a plant-based vegan diet exclusively. I intermittently fast, eating only during six to eight hours of the day. I don’t smoke. I drink only socially on occasion. I try to get more and better sleep. And I try to exercise as much as I can—at least five days a week. I used to be a runner, but I switched to doing more HIIT because I believe it probably has a bigger impact. I’ve also tried three cycles of the fasting-mimicking diet. I tracked my lab results for basic things, like blood glucose and inflammation markers, and saw improvement.

Morgan Levine, PhD, is an assistant professor of pathology at Yale School of Medicine who studies aging. Her work focuses on biological factors that affect aging, and she has developed various measures to calculate biological age.

This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The views expressed in this article are the views of the expert and do not necessarily represent the views of goop.


Abstract

Organic tomato growers in West Virginia and neighboring states suffer serious economic losses each year due to soil-borne wilt diseases caused by fungal pathogens including Verticillium dahliae. This study determined the efficacies of biological control agents (BCAs – Serenade SOIL and Prestop), bio-fumigants and transplants grafted to a resistant rootstock in suppressing wilt disease in heirloom tomato cv. Mortgage Lifter in a certified organic production system in West Virginia in two consecutive years. Prestop and Serenade treatments resulted in higher seedling vigor at the early stage. However, within 40 days of field set in the fungal pathogen infested soil, grafted transplants (on resistant rootstock Maxifort) had the highest vigor followed by BCA treatments, biofumigation with mustard cover crop and mustard meal and was lowest in nontreated control. All treatments showed significantly lower Verticillium wilt severity index than control except mustard cover crop and Prestop in 2015 and 2016, respectively. Total fruit harvested over a six-week period indicated that yield from all but mustard cover crop treatment were significantly (P < 0.001) higher compared to the nontreated control in 2015. However, results from 2016 indicated that mustard cover crop would work best for both disease suppression and yield enhancement when tissues were well macerated and incorporated immediately in the soil and covered with impervious plastic for up to 10 days. In 2016, all treatments except Prestop produced higher tomato yield than the nontreated control. In general, yield advantage over nontreated were in the order of grafted > bio-fumigation > BCA treatments > nontreated check. Between two BCAs, Bacillus subtilis (Serenade) consistently provided better disease suppression and improved yield compared with Gliocladium catenulatum (Prestop) in both years. Grafted plants produced 9.1 and 10.0 kg tomatoes/plant in 2015 and 2016, respectively, compared with only 5.0 kg in nontreated control. Our results suggest that grafted transplants, biofumigation and selected BCA should be useful for sustainable management of tomato wilt disease in organic production systems. An economic analysis indicated that grafted tomato can provide the greatest net revenue followed by mustard meal biofumigation in farms infested with wilt causing pathogen.


6. THE STERILITY OF MORGANISM-MENDELISM

THE Morganist-Weismannists, i.e., the adherents of the chromosome theory of heredity, have repeatedly asserted--without grounds whatever and often in a slanderous manner--that I, as President of the Academy of Agricultural Sciences, have used my office in the interests of the Michurin trend in science, which I share, to suppress the other trend, the one opposed to Michurin's.

Unfortunately, it has so far been exactly the other way round, and it is of that that I, as President of the All-Union Academy of Agricultural Sciences, may and should be accused. I have been wanting in strength and ability to make proper use of my official position to create conditions for the more extensive development of the Michurin trend in the various divisions of biological science, and to restrict, if only somewhat, the scholastics and metaphysicians of the opposite trend. As a matter of fact, therefore, the trend so far suppressed--suppressed by the Morganists--happens to be the one which the President represents, namely, the Michurin trend.

We, the Michurinists, must squarely admit that we have hitherto proved unable to make the most of the splendid possibilities created in our country by the Party and the Government for the complete exposure of the Morganist metaphysics, which is in its entirety an importation from foreign reactionary biology hostile to us. It is now up to the Academy, to which a large number of Michurinists have just been elected, to tackle this major task. This will be of considerable importance in the matter of training forces and providing more scientific aid to collective farms and state farms.

Morganism-Mendelism (the chromosome theory of heredity) is to this day taught, in a number of versions, in all colleges of biology and agronomy, whereas the study of Michurin genetics has in fact not been introduced at all. In the higher official scientific circles of biologists, too, the followers of the teaching of Michurin and Williams have often found themselves in the minority. They were a minority in the Lenin All-Union Academy of Agricultural Sciences, too. But the condition in the Academy has now sharply changed thanks to the interest taken in it by the Party, the Government, and Comrade Stalin personally. A considerable number of Michurinists have been elected members and corresponding members of our Academy, and more will be added shortly at the coming elections. This will create a new situation in the Academy and new opportunities for the further development of the Michurin teaching.

The assertion that the chromosome theory of heredity, with its underlying metaphysics and idealism, has hitherto been suppressed, is entirely wrong. The very opposite is the truth.

In our country the Morganist cytogeneticists find themselves confronted by the practical effectiveness of the Michurin trend in agrobiological science.

Aware of the practical worthlessness of the theoretical postulates of their metaphysical "science", and reluctant to give them up and to accept the vigorous Michurin trend, the Morganists have bent all their efforts to check the development of the Michurin trend which is inherently opposed to their pseudo-science.

It is a calumny to assert that somebody has been preventing the cytogenetic trend in biological science from associating itself with practical agriculture in our country. There is no truth whatever in the assertions to the effect that " the right to the practical application of the fruits of their labours has been a monopoly of Academician Lysenko and his followers ".

The Ministry of Agriculture might tell us exactly what the cytogeneticists have offered for practical application, and, if there have been such offers, whether they were accepted or rejected.

The Ministry of Agriculture might also tell us which of its scientific-research institutes (to say nothing of colleges) have not engaged in cytogenetics in general and, particularly, in the polyploidy of plants obtained by the application of colchicine.

I know that many institutes have been engaged and are engaged in this sort of activity which, in my view, is little productive. More, the Ministry of Agriculture set up a special institution, headed by A. R. Zhebrak, to study questions of polyploidy. I think that this institution, though it has for some years done nothing besides its work on polyploidy, has produced literally nothing of practical value.

Here is one example which might be cited to show how useless is the practical and theoretical programme of our domestic Morganist cytogeneticists.

Professor of Genetics, N. P. Dubinin, Corresponding Member of the Academy of Sciences of the U.S.S.R., who is regarded by our Morganists as the most eminent among them, has worked for many years to establish the differences in the cell nuclei of fruit flies in urban and rural localities.

For the sake of complete clarity, let us mention the following. What Dubinin is investigating is not qualitative alterations--in this case, in the nucleus of the cell--resulting from the action of qualitatively differing conditions of life. What he is studying is not the inheritance of characteristics acquired by fruit flies under the influence of definite conditions of life, but changes, recognisable in the chromosomes, in the make-up of the population of these flies as the result of the simple destruction of a part of them, for one thing, during the war. Dubinin and other Morganists call such destruction "selection". Such sort of "selection" identical with an ordinary sieve, which has nothing in common with the truly creative role of selection, is the subject of Dubinin's investigations.

His work is entitled: "Structural Variability of Chromosomes in Populations of Urban and Rural Localities."

Here are a few quotations from it:

" During the study of individual populations of D. funebris in the work of 1937 the fact was noted that there were noticeable differences as regards concentration of inversions. Tinyakov stressed this phenomenon on the basis of extensive material. However, only the 1944-45 analysis has shown us that these substantial differences are due to the differences of conditions of habitation in town and in countryside.

" The population of Moscow has eight different orders of genes. In the second chromosome there are four orders (one standard and three different inversions). One inversion in the III chromosome and one in IV . Inv. II--1 has its limits from 23 C to 31 B. Inv. II--2, from 29 A to 32 B. Inv. II--3, from 32 B to 34 C. Inv. III--I, from 50 A to 56 A. Inv. IV--1, from 67 C to 73 A/B. In the course of 1943-45 the karyotype of 3,315 individuals in the population of Moscow was studied. The population contained immense concentrations of inversions, which proved to be different in various sections Of Moscow." [14]

Dubinin went on with his investigations during and after the war and studied the problem of the fruit flies in the city of Voronezh and its environs. He writes:

"The destruction of industrial centres during the war upset the normal conditions of life. The drosophila populations found themselves in severe conditions of existence which, possibly, surpassed the severity of wintering in rural localities. It would be of profound interest to study the influence of the changes in the conditions of existence caused by the war upon the karyotypical structure of urban populations. In the spring of 1945 we studied populations from the city of Voronezh, one of those that suffered the worst destruction as the result of the German invasion. Among 225 individuals only two flies were found to be heterozygotal for inversion II--2 (0.88 per cent). Thus the concentration of inversions in this large city proved to be lower than in rural localities. We see here the disastrous action of natural selection upon the karyotypical structure of the population." [15]

Dubinin, as we see, writes so that on the surface his work may appear to some to be even scientific. As a matter of fact, this was one of the main works on the basis of which Dubinin was elected Corresponding Member of the Academy of Sciences of the U.S.S.R.

But if we were to put it all in plainer terms, stripping it of the pseudo-scientific verbiage and replacing the Morganist jargon with ordinary Russian words, we would arrive at the following:

As the result of many years of effort Dubinin "enriched" science with the "discovery" that during the war there occurred among the fruit-fly population of the city of Voronezh and its environs an increase in the percentage of flies with certain chromosome structures and a decrease in the percentage of dies with other chromosome structures (in the Morganist jargon that is called "concentration of inversions " II--2).

Dubinin is not content with these "highly valuable" discoveries from the theoretical and practical standpoint, which he made during the war. He sets himself further tasks for the period of recovery. He writes :

"It will be very interesting to study in the course of several coming years the restoration of the karyotypical structure of the urban population in connection with the restoration of normal conditions of life."

That is typical of the Morganists' "contribution" to science and practical activity before the war and during the war, and such are the vistas of the Morganist "science " for the period of recovery!


Discussion

Examples of mRNA movement across graft junctions were previously demonstrated in several model plant species [15, 19, 21, 38]. Long distance movement of a few mRNA species has also been documented in apple, including IAA14 and GAI [16, 17, 39]. Recently, extensive mRNA exchange was revealed between Arabidopsis and its parasitic plant C. pentagona through symplastic junctions [30, 31], between inter-generic grafts of Arabidopsis and tobacco [32], and between intra-specific (inter-ecotype) grafts of Arabidopsis through graft junctions [33]. However, these works were based on model and short-lived annual species and to what extent the conclusions from these studies can be applied to graft crops of economic significance is unknown. In this study, we advanced our knowledge in this area by extending the studies of mRNA exchange in model species to an important woody, fruit crop species of grapevines.

Genome-wide exchanges of mRNAs between graft partners

A total of 3333 annotated grape genes were found to produce mobile mRNAs across graft junctions in this study. They accounted for about 12.7 % of the total protein coding genes (26,346) in grape. The extent of mRNA exchange between graft partners revealed in this study was extensive, at a similar scale as what was recently reported in Arabidopsis (about 6 %, 2006 out of 33,602 genes, produced mobile mRNAs) [33]. Because detection of mobile RNAs is contingent on the availability of SNPs differentiating graft partners, sequencing coverage, mRNA stability, tissue sampling and other technical and biological factors, it would not be possible to detect all the mobile mRNAs and, therefore, the proportion of the genes that were found to produce mobile mRNAs in this study is likely underestimated.

A significant portion of the transmitting genes showed very low mRNA transmission rates in this study (Fig. 3). Because only a small number of mobile mRNAs were present in the receptor tissue, their biological significances, if any, were difficult to assess. However, there were some genes which transmitted their mRNAs with relatively high rates in different grafts. These mobile mRNAs, while their biological significances were unknown, were likely transmitted through certain selective processes. Conceivably, the numbers and species of mRNAs which are responsive to selective translocation will be different under different growth conditions. Another interesting observation in this study was that the mRNA transmission rates of the same genes from the same genotype were generally correlated well, but not so evident between different genotypes. This suggests that the donor genotype likely plays a key role in determining how frequently mobile transcripts are transmitted in a graft.

The transmitting genes discovered in this study were involved in many different biological processes (Additional file 2: Datasets S3, S5 and S6). Many of these processes were over-represented in both the in vitro and field graft transmitted genes, covering various basic cellular, biosynthetic, catabolic, and metabolic activities. It was interesting to note that many processes related to responses to various forms of stresses and stimuli, such as water, temperature and chemicals, were over-represented, suggesting that mRNA movement in the grafted grapevines in this study were responsive to growth conditions and environmental stresses. Additional evidence to support this hypothesis is that the in vitro and field grafts which were grown under different stress regimes had unique, additional stress-responsive genes involved. In the field grafts, mobile mRNAs from genes which were responsive to the stimulus of abscisic acid, carbohydrate, chitin, and organic substance were uniquely over-represented. In contrast, in the in vitro grafts, mRNAs from the genes responsive to cadmium ion, hormone, inorganic substance, metal ion, and salt stress were over-represented. In addition to this stress-responsive theme, we also found that many transcription factors and hormone-related genes participated in long-distance mRNA transmission, which presumably provide additional levels of regulations of many plant growth and development processes in the grafted plants.

We discovered that there were about 600 transmitting genes shared between the grapevines in this study and the Arabidopsis previously reported [33]. While these shared genes had diverse functions and were involved in many different biological processes, some of them were related to hormone transport, signal transduction and responses to certain forms of stresses and stimuli. Whether or not some of these genes are representative of the core common genes involved in producing and transmitting mRNAs in grafted plants is yet to be confirmed.

Impact of graft combinations, genotypes, and growth conditions on mRNA exchange

Impact of scion/rootstock combinations on macromolecular translocation has been reported before. The study on the graft transmission of phloem proteins in interspecific and intergeneric heterografts in the Cucurbitaceae family suggested that the direction of phloem protein translocation depended on the scion/rootstock combination [43]. Similarly, the mouse ear tomato mutant can induce leaf phenotypic changes in wild-type grafting partner only when the mutant was used as the rootstock [22]. On the other hand, in vitro reciprocal grafts between wild type and transgenic potato plants overexpressing the POTH1 gene demonstrated that the transgenic POTH1 only moved toward the rootstock [14]. Both directional and bi-directional exchanges of mRNAs between rootstocks and scions took place in grafted Arabidopsis [33]. We also observed such directional and bi-directional exchanges of mRNAs in the grafted grapevines in this study (Fig. 2), providing first support evidence from a woody species.

Overall, the number of mobile RNAs found in the field grafts was much smaller than that in the in vitro grafts. In addition, we observed that more rootstock mRNAs moved into the scion tissues in the in vitro reciprocal grafts. However, a reversed case was found in the field grafts. These differences could be attributed to different graft genotypes, different growth conditions (in vitro vs. field), different ages of graft material (4 weeks in vitro vs. 11 years in field), and different proximities of the scion and rootstock tissues to the graft junctions (few centimeters in vitro vs. several meters in field) (Additional file 1: Figure S1). Moreover, the in vitro grafts were grown on growth medium containing sucrose and other nutrients, thus the source-sink gradient for the in vitro grafts was not as apparent and effective as that in the field grafts. Furthermore, in the mature field grafts, mobile mRNAs from rootstocks would have to travel over a long distance to reach young scion shoots and therefore many of the mobile mRNAs from rootstocks might not reach that far before being degraded. Indeed, investigation of the distribution of a particular tomato host gene with high level of mobility along the stem of the parasitic plant (C. pentagona) revealed that the host gene transcript level decreased significantly from the basal section to the apical tip [30]. A similar gradient for RNA movement was also reported in Arabidopsis grafts [33]. These findings suggest that most mRNA species in the phloem stream might not be very stable or did not diffuse or migrate very far from the site where the message was generated, which offers a plausible explanation of why so few mobile RNAs were detected in the scion tissue of the field grafts in this study. Comparisons of the abundance, movement directions and patterns of mobile mRNAs in the in vitro and field grafts revealed an important fact that while many hundreds, perhaps even thousands, of genes could transmit their mRNAs between graft partners, only a small number of them might reach certain tissues to become biologically relevant. Such comparisons also reinforced that research results of mRNA exchange from model species and certain experimental material, such as the in vitro grafts in this study, were invaluable, but special cautions are needed to interpret the results, especially when extending the conclusions beyond the system studied.

Genotypes, scion/rootstock combinations, and growth conditions not only affected the scale or extent of the mRNA exchange, but also had significant impact on the species of mRNAs transmitted. We revealed that many biological processes conferred by the mobile mRNAs were shared by different genotypes, graft partners, and grafts grown in different conditions, but at the same time, there were many processes uniquely over-represented under certain biological and environmental conditions. The genetic and physiological bases for these graft-, genotype- and environment-dependent mRNA movements are yet to be elucidated. Future studies in this area are certainly of great interest not only to the understanding of the molecular and genetic mechanisms regulating the process of mRNA movement in grafted plants, but also to the development and selection of superior grafts for practical agricultural uses.

MRNA movement mechanisms

While many mRNAs were detected in phloem saps in plants [8, 9, 11, 12, 38, 39], few were found with known necessity of long distance trafficking to carry out their functions. A closer examination of the macromolecules detected in phloem sap showed that many of these molecules are quite abundant in plants in general [44–46]. Many components for protein translation and protein degradation were detected in phloem stream but may have no necessary function there and were ‘leaked’ or diffused passively into the phloem stream simply due to their abundant quantity in plants [1]. All these work suggested that ‘spill over’ was likely a cause for the presence of a large number of macromolecules, including mRNAs, in the plant phloem system. The detection of host non-phloem mobile transcripts in the parasitic plant tissues of C. pentagona also provided supporting evidence of such possible ‘spill over’ of abundant transcripts from cells to cells [30, 31]. The fact that more than 10 % of the graft transmitting genes showed very low transmission rates in this study (less than 0.001, Fig. 3c) also suggests the existence of a genome-wide, non-selective mass flow mechanism involved in the mRNA movement across graft junctions of grapevines (Fig. 3). For example, many genes coding for ribosome components were found to transmit their mRNAs across graft junctions at low transmission rates and they were over-represented in both field and in vitro graft transmitted genes (Additional file 2: Datasets S3, S5 and S6). This structural constituent of ribosome is a common component observed in almost all studies of phloem mRNA populations [8, 9, 11, 39]. The presence of such mRNAs in phloem sap samples could be explained by the passive mass flow into the phloem stream, since many of those transcripts were ubiquitously expressed in all plant parts and there would be no biological necessity for such messages to be selectively translocated across the graft junction into a grafting partner.

Active long-distance mRNA trafficking has been reported for StBEL5 in potato and GAI in Arabidopsis [15, 20, 21]. Selective movement of mRNAs across graft junctions was recently demonstrated in the grafted Arabidopsis [33]. In this study, we observed that some genes had their mobile RNAs detected in the field grafts, but not in the in vitro grafts, even though they had diagnostic SNPs and were expressed at comparable levels as that in the field grafts. Why the mRNAs of these genes were transmitted across graft junctions in the field grafts, not in the in vitro grafts, is unknown, but some types of selective processes, including those dependent on genotypes, growth conditions and age of grafts, might have been involved. We also observed that some genes produced mobile mRNAs transmitted only to one graft partner, but not to the other, suggesting that some selective processes might be involved in promoting or inhibiting the movement of these mRNAs towards a particular graft partner or direction. Additional evidence for supporting the existence of selective process in mobile mRNA movement in this study came from the fact that some genes were expressed at relative low levels, but their mRNAs were transmitted at the rates higher than expected by random transmission (Fig. 3). These genes might contain some intrinsic elements facilitating their long distance trafficking as reported by others [21, 25].


Adaptation

Cell biology
The constellation of processes by which an organism adjusts to a new or altered environment in response to stress and increased physiologic demands.

Dentistry
(1) The proper fitting of a denture.
(2) The degree of proximity and interlocking of restorative material to a tooth ‘prep’.

Evolutionary biology
A phenotypic feature which improves the reproductive success of a species.

Microbiology
The adjustment of bacteria to a new or altered environment.

Molecular biology
The change in the response of a subcellular system over time functional or structural changes that allow an organism to respond to changes in the environment the ability to physiologically adjust to a new environment&mdashtypically, cells de-adapt when transferred to different growth conditions.

Ophthalmology
The ability of the eye to adjust to variations in light intensity.

Orthodontics
An adjustment of corrective bands resulting in a shifting of the teeth.

Physiology
A reduction in the frequency of neuronal firing under conditions of constant stimulation.


Watch the video: Τελομερή και Αντιστροφή της Βιολογικής Ηλικίας (July 2022).


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