The reprogramming of epigenetic states in gametes and embryos is essential for correct development in plants and mammals1. In plants, the germ line arises from somatic tissues of the flower, necessitating the erasure of chromatin modifications that have accumulated at specific loci during development or in response to external stimuli. If this process occurs inefficiently, it can lead to epigenetic states being inherited from one generation to the next2, 3, 4. However, in most cases, accumulated epigenetic modifications are efficiently erased before the next generation. An important example of epigenetic reprogramming in plants is the resetting of the expression of the floral repressor locusFLC in Arabidopsis thaliana. FLC is epigenetically silenced by prolonged cold in a process called vernalization. However, the locus is reactivated before the completion of seed development, ensuring the requirement for vernalization in every generation. In contrast to our detailed understanding of the polycomb-mediated epigenetic silencing induced by vernalization, little is known about the mechanism involved in the reactivation of FLC. Here we show that a hypomorphic mutation in the jumonji-domain-containing protein ELF6 impaired the reactivation of FLC in reproductive tissues, leading to the inheritance of a partially vernalized state. ELF6 has H3K27me3 demethylase activity, and the mutation reduced this enzymatic activity in planta. Consistent with this, in the next generation of mutant plants, H3K27me3 levels at the FLC locus stayed higher, and FLC expression remained lower, than in the wild type. Our data reveal an ancient role for H3K27 demethylation in the reprogramming of epigenetic states in plant and mammalian embryos5, 6, 7.
Improving wheat is a major challenge for agricultural scientists. The world’s population continues to grow – and so does its appetite. Sanjaya Rajaram, winner of the 2014 World Food Prize, used an innovative breeding technique to develop 480 new wheat varieties. Rajaram’s varieties are high-yielding yet resistant to diseases and stresses, which allows them to thrive in a range of environments. Across the world, scientists are currently exploring a range of strategies to increase wheat yield.
While healthy people have proteins in their blood called clotting factors that act quickly to plug wounds, hemophiliacs lack these proteins, making even minor bleeds difficult to stop.
The main treatment option for people with severe hemophilia is to receive regular infusions of clotting factor. But 20 to 30 percent of people who get these infusions develop antibodies, called inhibitors, against the clotting factor. Once these inhibitors develop, it can be very difficult to treat or prevent future bleeding episodes.
In a new study, researchers from the University of Pennsylvania School of Dental Medicine and theUniversity of Florida College of Medicine teamed up to develop a strategy to prevent these antibodies from forming. Their approach, which uses plant cells to teach the immune system to tolerate rather than attack the clotting factor protein, offers hope for preventing one of the most serious complications of hemophilia treatment.
Zygotic genome activation in metazoans typically occurs several hours to a day after fertilization, and thus maternal RNAs and proteins drive early animal embryo development. In plants, despite several molecular studies of post-fertilization transcriptional activation, the timing of zygotic genome activation remains a matter of debate. For example, two recent reports that used different hybrid ecotype combinations for RNA sequence profiling of early Arabidopsis embryo transcriptomes came to divergent conclusions. One identified paternal contributions that varied by gene, but with overall maternal dominance, while the other found that the maternal and paternal genomes are transcriptionally equivalent. Here we assess paternal gene activation functionally in an isogenic background, by performing a large-scale genetic analysis of 49 EMBRYO DEFECTIVE genes and testing the ability of wild-type paternal alleles to complement phenotypes conditioned by mutant maternal alleles. Our results demonstrate that wild-type paternal alleles for nine of these genes are completely functional 2 days after pollination, with the remaining 40 genes showing partial activity beginning at 2, 3 or 5 days after pollination. Using our functional assay, we also demonstrate that different hybrid combinations exhibit significant variation in paternal allele activation, reconciling the apparently contradictory results of previous transcriptional studies. The variation in timing of gene function that we observe confirms that paternal genome activation does not occur in one early discrete step, provides large-scale functional evidence that maternal and paternal genomes make non-equivalent contributions to early plant embryogenesis, and uncovers an unexpectedly profound effect of hybrid genetic backgrounds on paternal gene activity.
Entering into a symbiotic relationship is not something to be taken lightly. Previously free-living organisms become beholden to each other and have to tolerate invasion of their personal space to accommodate varying degrees of intimacy, especially when one partner lives within the body or even the cells of the other. Symbiosis brings with it so many potential mutual benefits that it has arisen independently many times in evolution, but overcoming these barriers requires some encouragement.
In photosynthetic organisms, d-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the major enzyme assimilating atmospheric CO2 into the biosphere. Owing to the wasteful oxygenase activity and slow turnover of Rubisco, the enzyme is among the most important targets for improving the photosynthetic efficiency of vascular plants. It has been anticipated that introducing the CO2-concentrating mechanism (CCM) from cyanobacteria into plants could enhance crop yield. However, the complex nature of Rubisco/'s assembly has made manipulation of the enzyme extremely challenging, and attempts to replace it in plants with the enzymes from cyanobacteria and red algae have not been successful. Here we report two transplastomic tobacco lines with functional Rubisco from the cyanobacterium Synechococcus elongatus PCC7942 (Se7942). We knocked out the native tobacco gene encoding the large subunit of Rubisco by inserting the large and small subunit genes of the Se7942 enzyme, in combination with either the corresponding Se7942 assembly chaperone, RbcX, or an internal carboxysomal protein, CcmM35, which incorporates three small subunit-like domains. Se7942 Rubisco and CcmM35 formed macromolecular complexes within the chloroplast stroma, mirroring an early step in the biogenesis of cyanobacterial [bgr]-carboxysomes. Both transformed lines were photosynthetically competent, supporting autotrophic growth, and their respective forms of Rubisco had higher rates of CO2 fixation per unit of enzyme than the tobacco control. These transplastomic tobacco lines represent an important step towards improved photosynthesis in plants and will be valuable hosts for future addition of the remaining components of the cyanobacterial CCM, such as inorganic carbon transporters and the [bgr]-carboxysome shell proteins.
A number of research groups in various areas of plant biology as well as computer science and applied mathematics have addressed modelling the spatiotemporal dynamics of growth and development of plants. This has resulted in development of functional–structural plant models (FSPMs). In FSPMs, the plant structure is always explicitly represented in terms of a network of elementary units. In this respect, FSPMs are different from more abstract models in which a simplified representation of the plant structure is frequently used (e.g. spatial density of leaves, total biomass, etc.). This key feature makes it possible to build modular models and creates avenues for efficient exchange of model components and experimental data. They are being used to deal with the complex 3-D structure of plants and to simulate growth and development occurring at spatial scales from cells to forest areas, and temporal scales from seconds to decades and many plant generations. The plant types studied also cover a broad spectrum, from algae to trees. This special issue of Annals of Botany features selected papers on FSPM topics such as models of morphological development, models of physical and biological processes, integrated models predicting dynamics of plants and plant communities, modelling platforms, methods for acquiring the 3-D structures of plants using automated measurements, and practical applications for agronomic purposes.
Genetically engineered bacteria could one day be harnessed to make renewable propane fuel.
Patrik Jones at Imperial College London, Kalim Akhtar at University College London and their colleagues introduced genes for various enzymes from different species of bacteria into Escherichia coli, so that the microbe could convert glucose into propane gas. With genetic tinkering and by increasing the levels of oxygen to which the engineered bacterium was exposed, the team boosted propane production by two orders of magnitude.
Propane is an ideal biofuel because as a gas, it can be separated from the cultivation medium and easily liquefied for efficient storage, the authors say.
The UK Plant Sciences Federation is looking for suggestions from you! The concerns are not restricted to the UK (lack of student interest and teacher preparedness, lack of funding and job opportunities etc), so wherever you are please share your insights and solutions.
How do you model a plant? By modeling pieces and assembling them in a meaningful way. Here's a multiscale model that works. From the abstract:
"Our model brings together gene dynamics, carbon partitioning, organ growth, shoot architecture, and development in response to environmental signals. It predicted the biomass of each leaf in independent data, demonstrated flexible control of photosynthesis across photoperiods, and predicted the pleiotropic phenotype of a developmentally misregulated transgenic line. Systems biology, crop science, and ecology might thus be linked productively in a community-based approach to modeling."