From its identification and characterization of the BARE retrotransposon in 1993, the Schulman group has focused on the structure, function, evolution, and dynamics of retrotransposons. Remarkably, the most abundant gene family in plants and animals codes for reverse transcriptase and the majority of most genomes is comprised of reverse-transcribed DNA. This is because the most abundant repetitious components of plant genomes are the long-terminal-repeat (LTR) retrotransposons (RLXs), which form the bulk of the transposable elements (TEs). RLXs form >70% of genomes of average size (4.7 Gb monoploid). The proportion that RLXs comprise in any particular genome results from a balance between gain by replicative propagation and loss by recombination and deletion.
Our research in this area includes:
Work to sequence and assemble the genomes of crop species and the wild relatives provides abundant benefits. Discovery of the full complement of genes and their regulatory regions, the basis of variation in key traits and their control, as well understanding genome structure and evolution, all require a well-assembled genome. As sequencing technologies and assembly approaches have improved, we have moved progressively from a small model genome, Brachypodium distachyon, for the small-grain cereals, to the large and complex genomes of barley and now oat and faba bean. We have played a major role in annotating the retrotransposons in these genome projects, and uncovered striking insights into genome evolution:
Crop production and yield depend largely upon photosynthesis and nutrient acquisition in the face of daily and seasonal environmental fluctuations regarding water, temperature, light, and nutrient supply. The strategic challenge for plant breeders is to maximize yield (and quality) by minimizing losses due to environmental constraints. However, environmental stresses (e.g. water availability, temperature fluctuations, nitrogen shortage), exacerbated by climate change, are of increasing concern for sustainable crop production. Plant perception and responses to the external environment are mediated by molecular signaling and physiological circuits underpinned by genetic control networks that interact with plant development, architecture and phenology. Thanks to the availability of high-quality genome sequences and new genetic tools, stress response networks can now be clarified directly in crop species, paving the link between stress response and agricultural yield.
We must produce not only environmentally sustainable and stress-resilient crops, but also ones that provide the basis for a nutritious diet. Plant protein crops suitable for cultivation in each region, which can be used directly as food for people, are a key. We work on nitrogen-fixing pulse crops, in particular faba bean for Finland and northern Europe, as an answer to this need.