Meiotic adaptation to whole genome duplication in Arabidopsis arenosa

The information to make an organism is encoded in DNA. DNA is organized into individual chromosomes so that it can be accessed, copied and easily moved. In nature, especially in the plant kingdom, organisms may experience duplication of all the chromosomes. This is often advantageous as the organisms may become bigger and better adapted to challenging environments. In fact, humans have been subconsciously selecting plants with extra sets of chromosomes, such as bread wheat, sugar cane, cotton, coffee, strawberry, banana, oil seed rape and potato. This has produced larger, more nutritious crops through a completely natural process. However, upon producing an organism with a doubled set of chromosomes there is an immediate problem. As the doubled sets of chromosomes may be identical or very similar, they get tangled up during a particular stage of sexual reproduction called meiosis. This causes infertility and limits the potential for generating novel, high yielding crops. However, evolution has repeatedly solved this problem, by innovating or selecting advantageous natural variation. We are now in a position to understand how natural variants of certain genes can ensure that chromosomes do not tangle after doubling, to produce fertile plants. The aim of this work is to functionally characterize these natural gene variants in the model plant Arabidopsis. We will use chromosome doubling and halving techniques as well as molecular and cell biology approaches so that we can understand the mechanism behind chromosome stabilization and translate this knowledge to produce bigger, high yielding crop plants. A second aspect of this project is to determine whether the factors controlling chromosome stabilization are the same in closely related species to Arabidopsis. This will reveal whether the same or different factors may be targeted, which will be of academic and agronomic interest.

Whole genome duplication (WGD) provides the raw material for evolution by allowing redundant genes to diversify into new functions. It contributes to increased cell size, organismal complexity, adaptive radiation, speciation, and genomic novelty. Although WGD has the potential to occur throughout eukaryotes, it is most prevalent in the plant kingdom. Due to the benefits of increased size, it is unsurprising that a large number of economically important crop plants have undergone recent WGD, including wheat, oats, potato, oil seed rape, maize, banana and cotton. However, WGD severely challenges reliable chromosome segregation during meiosis as the doubled set of chromosomes may be indistinguishable to the meiotic recombination machinery. Meiotic instability leads to aberrant chromosome configurations such as multivalents and interlocks at metaphase I, resulting in chromosome mis-segregation, genome rearrangements and loss of fertility. Despite this evolutionary 'bottleneck', meiotically stable 'diploidized' polyploid species are found in nature, indicating that these problems can be overcome. In this proposal we aim to understand the mechanisms underlying the stabilization of meiotic chromosomes after WGD and thus provide novel insights into the evolution of the meiotic recombination machinery and how it can be modified to stabilize chromosome segregation in polyploid plants.

The proposed project fulfils several BBSRC strategic aims: "maintaining world-class UK Bioscience by supporting the best people and best ideas", "providing skilled researchers needed for academic research". It has particular relevance to BBSRC's strategic priorities in regards to crop breeding/food security. Plant breeding is reliant on the creation of genetic variation that arises during meiotic recombination. It has been known for some time that large segments of chromosomes in crop species, notably cereals, rarely recombine. This is a serious barrier to the breeding of lines with new traits. Thus there is a real need to understand the major factors that control the frequency and distribution of meiotic crossovers during recombination. An additional issue, that is particularly relevant to plants including key crops such as wheat and oilseed rape, is that they are polyploids. Although we know something about the genetic loci that are important for meiotic stability in these species, such as Ph1 in wheat and BHP1 in B. napus, our understanding of how accurate homologous chromosome pairing is established remains to be established. This project is designed to increase our fundamental understanding of the mechanistic basis of these complex issues, thus providing a platform for future translational studies. Our fundamental work on Arabidopsis meiosis directly led to translational work conducted in barley BBSRC LOLA project (BB/F019351), which was selected for the BBSRC website news and events section (http://www.bbsrc.ac.uk/news/food-security/2012/121214-f-turning-up-heat-on-plant-sex.aspx). We have links with a number of breeding companies and have regularly attended annual meetings such as Monogram, where we have presented talks and posters (and written a blog for the monogram website). We propose to continue this as these meetings provide an ideal forum to present our work to wider crop research community and to plant breeders. There has been such interest in this work that the PI has recently submitted a BBSRC industrial CASE studentship with UK plant breeding company KWS.

We have been actively involved in interacting with the end-users, media, public and schools to make science more accessible for many years. The PI has been involved in activities at "ThinkTank" (Science and Technology museum in Birmingham), demonstrating the use of microscopes for observing the behaviour of chromosomes in a "hands-on" experience for the public. The PI was also part of a similar event at the International Plant Sexual Reproduction meeting in Bristol in 2010. At the University of Leicester we also benefit from the GENIE (Genetics Education Networking for Innovation and Excellence) Centre for Excellence in Teaching and Learning (CETL). GENIE is an effective tool to continue the department's passion for science by disseminating new discoveries beyond academia, and will create a learning experience that is both innovative and intellectually exciting. We will work closely with GENIE to promote public awareness of science and widening participation in science education.