The role of E3 ligases on the modulation of recombination in cereals

Supervisors: Robbie Waugh, Isabelle Colas (Luke Ramsay)

Project Description:

In barley and wheat substantial proportions of the chromosomes are inherited together as a large linkage block, preventing the generation of novel gene combinations and useful variation that could be exploited in breeding and genetics programs. In these crops, the distribution of meiotic crossover events is skewed toward the telomere regions meaning that up to half of the genes rarely if ever recombine.

Meiotic recombination is highly controlled to ensure species genome integrity. Recent findings have described anti-crossover factors such as FANCM, RECQ4 or FIGL1, that, once downregulated, increase meiotic recombination in Arabidopsis. Utilizing the barley mutant collection held at the James Hutton, we mapped a spontaneous mutation, des12, and identified a novel causal gene. Despite semi-fertility, abnormal synapsis caused by unresolved interlocks and sticky metaphases, barley seed are still produced. Moreover, F3 genetic analysis revealed that recombination is significantly increased in the distal regions suggesting that this gene is a novel anti-crossover factor that has not yet been described.  It appears to be a grass specific gene that we called HvST1 and likely functions as an E3 Ubiquitin Ligase.  The causal mutation is due to slippage in a small mononucleotide microsatellite motif before the RING domain that knocks the coding sequence out of frame.  In this project we aim to investigate the mode of action of HvST1 in controlling crossovers in barley.

1.    Isabelle Colas*, Benoit Darrier*, Mikel Arrieta, Sybille Mittmann, Luke Ramsay, Pierre Sourdille and Robbie Waugh. Observation of extensive chromosome axis remodelling during the ‘diffuse-phase’ of meiosis in large genome cereals. (2017) Front Plant Sci. 13;8:1235.
2.    Isabelle Colas, Malcolm Macaulay, James D. Higgins, Dylan Phillips, Abdellah Barakate, Markus Posch, Sue J. Armstrong, F. Chris H. Franklin, Claire Halpin, Robbie Waugh, and Luke Ramsay. A spontaneous mutation in MutL-Homolog 3 (HvMLH3) affects synapsis progression and crossover resolution in the barley desynaptic mutant des10. (2016) New Phytol. 212(3):693-707.
3.    Phillips, D., Jenkins, G., Macaulay, M., Nibau, C., Wnetrzak, J., Fallding, D., Colas, I., Oakey, H., Waugh, R., & Ramsay, L. (2015). The effect of temperature on the male and female recombination landscape of barley. New Phytologist, 208(2):421-9.

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