Increasing longevity of seeds with genetic engineering

A study developed by researchers of the Institute for Plant Molecular and Cell Biology (IBMCP), a joint center of the Universitat Politcnica de Valncia and the Spanish National Research Council (CSIC), in collaboration with the Unit for Plant Genomics Research of Evry, France (URGV, in French) has discovered a new way of improving the longevity of plant seeds using genetic engineering. Plant Physiology magazine has published the research results.The key is the overexpression of the ATHB25 gene. This gene encodes a protein that regulates gene expression, producing a new mutant that gives the seed new properties. Researchers have proven that this mutant has more gibberellin -the hormone that promotes plant growth-, which means the seed coat is reinforced as well. “The seed coat is responsible for preventing oxygen from entering the seed; the increase in gibberellin strengthens it and this leads to a more durable and longer lasting seed,” explains Eduardo Bueso, researcher at the IBMCP (UPV-CSIC).This mechanism is new, as tolerance to stresses such as aging has always been associated with another hormone, abscisic acid, which regulates defenses based on proteins and small protective molecules, instead of producing the growth of structures like gibberellin does.The study has been made on the experimental model plant Arabidopsis thaliana, a species that presents great advantages for molecular biology research. Researchers of the IBMCP traced half a million seeds, related to one hundred thousand lines of Arabidopsis mutated by T-DNA insertion, using the natural system of Agrobacterium tumefaciens. “Finally, we analyzed four mutants in the study and we proved the impact on the seed longevity when the overexpression of the ATHB25 gene is introduced,” states Ramn Serrano, researcher at the IBMCP.Researchers compared the longevity of genetically modified Arabidopsis seeds and seeds which were not modified. In order to do this, they preserved them for thirty months under specific conditions of room temperature and humidity. After thirty months, only 20% of the control plants germinated again, whereas almost the all of the modified plants (90%) began the germination process again.Researchers of the IBMCP are now trying to improve the longevity of different species that are of agronomical interest, such as tomatoes or wheat.Biodiversity and benefits for farmersThis discovery is particularly significant for the conservation of biodiversity, preserving seed species and, especially, for farmers.”In the past, a lot of different plant species were cultivated, but many of them are dissapearing because high performance crops have now become a priority. Seed banks were created in order to guarantee the conservation of species, but they require a periodical regeneration of the seeds. …

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Sugarcane converted to cold-tolerant, oil-producing crop

A multi-institutional team reports that it can increase sugarcane’s geographic range, boost its photosynthetic rate by 30 percent and turn it into an oil-producing crop for biodiesel production.These are only the first steps in a bigger initiative that will turn sugarcane and sorghum — two of the most productive crop plants known — into even more productive, oil-generating plants.The team will present its latest findings Tuesday (Feb. 25) at the U.S. Department of Energy’s ARPA-E Energy Innovation Summit in Washington, D.C.”Biodiesel is attractive because, for example, with soybean, once you’ve pressed the oil out it’s fairly easy to convert it to diesel,” said Stephen P. Long, a University of Illinois professor of plant biology and leader of the initiative. “You could do it in your kitchen.”But soybean isn’t productive enough to meet the nation’s need for renewable diesel fuels, Long said.”Sugarcane and sorghum are exceptionally productive plants, and if you could make them accumulate oil in their stems instead of sugar, this would give you much more oil per acre,” he said.Working first with the laboratory-friendly plant Arabidopsis and later with sugarcane, the team introduced genes that boost natural oil production in the plant. They increased oil production in sugarcane stems to about 1.5 percent.”That doesn’t sound like a lot, but at 1.5 percent, a sugarcane field in Florida would produce about 50 percent more oil per acre than a soybean field,” Long said. “There’s enough oil to make it worth harvesting.”The team hopes to increase the oil content of sugarcane stems to about 20 percent, he said.Using genetic engineering, the researchers increased photosynthetic efficiency in sugarcane and sorghum by 30 percent, Long said. And to boost cold tolerance, researchers are crossing sugarcane with Miscanthus, a related perennial grass that can grow as far north as Canada. The new hybrid is more cold-tolerant than sugarcane, but further crosses are needed to restore the other attributes of sugarcane while preserving its cold-tolerance, Long said.Ultimately, the team hopes to integrate all of these new attributes into sugarcane, he said.”Our goal is to make sugarcane produce more oil, be more productive with more photosynthesis and be more cold-tolerant,” he said.Story Source:The above story is based on materials provided by University of Illinois at Urbana-Champaign. The original article was written by Diana Yates. …

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Revolutionary new view on heritability in plants: Complex heritable traits not only determined by changes in DNA sequence

Complex heritable traits are not only determined by changes in the DNA sequence. Scientists from the University of Groningen Bioinformatics Centre, together with their French colleagues, have shown that epigenetic marks can affect traits such as flowering time and architecture in plants. Furthermore, these marks are passed on for many generations in a stable manner. Their results were published in Science on the 6th of February 2014. It seems that a revision of genetics textbooks is now in order.We’ve all been taught that DNA is the physical foundation of heredity. Our genes are spelled out in the four famous letters A, T, C and G, which together form the genetic code. A single letter change in this code can lead to a gene ceasing to function or failing to work properly.The fact that the functioning of our genes is also affected by epigenetic marks has been known for decades. For example, the nucleotide cytosine (the C in the genetic code) can be changed into a methylcytosine. This cytosine methylation, which is one type of epigenetic mark, is typically associated with repression of gene activity.Epigenetic inheritance’While in mammals epigenetic marks are typically reset every generation, in plants no such dramatic resetting takes place. This opens the door to epigenetic inheritance in plants: epigenetic changes that are acquired in one generation tend to be stably passed on to the next generation’, explains Frank Johannes, assistant professor at the GBIC and co-lead scientist for the Science study.Johannes’s French colleagues have produced inbred strains of the model plant Arabidopsis, in which the epigenetic marks vary between strains although the DNA sequence is almost identical. …

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Model plant misled scientists about multicellular growth

Oct. 22, 2013 — Scientists have misunderstood one of the most fundamental processes in the life of plants because they have been looking at the wrong flower, according to University of Leeds researchers.Arabidopsis thaliana — also known as thale cress or mouse-ear cress — grows abundantly in cracks in pavements all over Europe and Asia, but the small white flower leads a second life as the lab rat of the plant world.It has become the dominant “model plant” in genetics research because of its simple genetics and ease of use in a research environment. Thousands of trays of the humble weed are cultivated in laboratories across the world, but it turns out they may actually contain a rather oddball plant.A study by researchers at the University of Leeds found that Arabidopsis thaliana was exceptional in not having a “censorship” protein called SMG1.SMG1 was known to play a vital role in the growth of animals as multicellular organisms, but scientists thought that plants built their complex life fundamentally differently. That conclusion, it turns out, was built on a dummy sold by Arabidopsis thaliana.Professor Brendan Davies from the University of Leeds’ School of Biology, who led the study, said: “Everybody thought that this protein was only in animals. They thought that because, basically, most of the world studies one plant: Arabidopsis thaliana.”Gene expression — the process by which the information from a genome is converted into the differentiated cells that make up complex life — relies on processes that turn genes on, when their genetic messages are required, and off when they are not.”Switching genes on and off is really what life is about. If you can’t do that, you can’t have life,” said Professor Davies. “There are various ways this is done, but one way in more complex life such as animals and plants is through a sort of ‘censorship’ process. The system looks at the messages that come out of the nucleus and effectively makes a judgement on them. It says ‘I am going to destroy that message now’ and intervenes to destroy it before it takes effect.”Scientists know that this “censorship” process — called Nonsense Mediated mRNA Decay (NMD) — is used by both plants and animals, but thought the two types of organism did it in different ways.Because Arabidopsis thaliana does not have SMG1, which plays a key role in triggering the censorship system in animals, scientists had concluded that SMG1 was not present in any plant.However, the Leeds researchers discovered that the plant that has established itself as the standard reference plant for all of biology is in fact an anomaly.”We have found that SMG1 is in every plant for which we have the genome apart from Arabidopsis and we have established that it is being used in NMD. Rather than being just in animals, we are suggesting that the last common ancestor of animals and plants had SMG1,” Professor Davies said.The study also found SMG1 in Arabidopsis lyrata, a close relative of Arabidopsis thaliana, which suggests that the missing protein has been lost relatively recently in evolutionary time, perhaps in the last 5-10 million years.The next key question for researchers is to explain how organisms without SMG1, such has funghi and Arabiposis thaliana, work without the protein.As for Arabidopsis thaliana, it may not have met its Waterloo just yet. …

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Genes outside nucleus have disproportionate effect

Oct. 12, 2013 — New research from the University of California, Davis, shows that the tiny proportion of a cell’s DNA that is located outside the cell nucleus has a disproportionately large effect on a cell’s metabolism. The work, with the model plant Arabidopsis, may have implications for future treatments for inherited diseases in humans.Plant and animal cells carry most of their genes on chromosomes in the nucleus, separated from the rest of the cell. However, they also contain a small number of genes in organelles that lie outside the nucleus. These are the mitochondria, which generate energy for animal and plant cells, and chloroplasts, which carry out photosynthesis in plant cells.The influence of genes outside the nucleus was known to an earlier generation of field ecologists and crop breeders, said Dan Kliebenstein, professor in the UC Davis Department of Plant Sciences and Genome Center and senior author on the paper published Oct. 8 in the online journal eLife. This is the first time that the effect has been quantified with a genomic approach, he said.Bindu Joseph, a postdoctoral researcher in Kliebenstein’s lab, and Kliebenstein studied how variation in 25,000 nuclear genes and 200 organellar genes affected the levels of thousands of individual chemicals, or metabolites, in leaf tissue from 316 individual Arabidopsis plants.They found that 80 percent of the metabolites measured were directly affected by variation in the organellar genes — about the same proportion that were affected by variation among the much larger number of nuclear genes. There were also indirect effects, where organellar genes regulated the activity of nuclear genes that in turn affected metabolism.”At first it’s surprising, but at another level you almost expect it,” Kliebenstein said. “These organelles produce energy and sugar for cells, so they are very important.”Similar effects could also occur in mammalian cells, Kliebenstein said. That has implications for in vitro fertilization therapies aimed at preventing diseases caused by faulty mitochondria being passed from mother to child. …

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How petals get their shape: Hidden map located within plant’s growing buds

Apr. 30, 2013 — Why do rose petals have rounded ends while their leaves are more pointed? In a new study published April 30 in the open access journal PLOS Biology, scientists from the John Innes Centre and University of East Anglia, UK, reveal that the shape of petals is controlled by a hidden map located within the plant’s growing buds.

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Leaves and petals perform different functions related to their shape. Leaves acquire sugars for a plant via photosynthesis, which can then be transported throughout the plant. Petals develop later in the life cycle and help attract pollinators. In earlier work, this team had discovered that leaves in the plant Arabidopsis contain a hidden map that orients growth in a pattern that converges towards the tip of the bud, giving leaves their characteristic pointed tips. In the new study, the researchers discover that Arabidopsis petals contain a similar, hidden map that orients growth in the flower’s bud. However, the pattern of growth is different to that in leaves — in the petal growth is oriented towards the edge giving a more rounded shape — accounting for the different shapes of leaves and petals. The researchers discovered that molecules called PIN proteins are involved in this oriented growth, which are located towards the ends of each cell.

“The discovery of these hidden polarity maps was a real surprise and provides a simple explanation for how different shapes can be generated,” said Professor Enrico Coen, senior author of the study.

The team of researchers confirmed their ideas by using computer simulations to test which maps could predict the correct petal shape. They then confirmed experimentally that PIN proteins located to the right sites to be involved in oriented growth, and identified that another protein, called JAGGED, is involved in promoting growth towards the edge of petals and in establishing the hidden map that determines petal growth and shape.

Unlike animal cells, plant cells are unable to move and migrate to form structures of a particular shape, and so these findings help to explain how plants create differently shaped organs — by controlling rates and orientations of cell growth. From an evolutionary perspective, this system creates the flexibility needed for plant organs to adapt to their environment and to develop different functions.

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The above story is reprinted from materials provided by Public Library of Science.

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Journal Reference:

  1. Sauret-Güeto S, Schiessl K, Bangham A, Sablowski R, Coen E (2013) . JAGGED Controls: Arabidopsis Petal Growth and Shape by Interacting with a Divergent Polarity Field. PLoS Biol, 2013 DOI: 10.1371/journal.pbio.1001550

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