Plant Genomes in a Changing Environment 2019 (III)

The zygotic transition in rice and application to self-propagating hybrid crops (Venkatesan Sundaresan, University of California- Davis, USA)

He reviews animal embryogenesis, where the zygotic nucleous is not transcribed for several cell divisions but then gets gradually activated. Less is known about the maternal to zygotic transition in plants. Rice is a nice model for this, as it takes 30min from pollination to fertilization. They observed that zygotic activation is quicker than in animals, with 8 cells (https://www.ncbi.nlm.nih.gov/pubmed/29112853). They have shown that an AP2 baby boom transcription factor expressed in the sperm cell triggers embryogenesis. 

In the second part of the talk he talks about their work on obtaining cheap hybrid rice obtained from mutants that turn meiosis in mitosis, as currently farmers worldwide cannot afford to buy hybrid seed. These mutant synthetic apomictic plants produce seed that maintain parents heterozygosity with <30 at="" described="" efficiency="" is="" span="" the="" work="">https://www.nature.com/articles/s41586-018-0785-8.  He discusses the risks of having clonal crops with the banana example (Gros Michel, Cavendish, …) and their disease susceptibilities.

During questions he explains that there natural apomictic species and in pearl millet it is known that the responsible gene is a baby boom TF.

The genetics of plant-plant interactions: from monospecific to community-wide interactions (Fabrice Roux, INRA, France)

Plants do not grow in isolation, they usually compete for space and resources. In fact, most pesticides used by farmers are herbicides, as plants compete with neighbor plants from the same or other species to thrive (https://onlinelibrary.wiley.com/doi/full/10.1111/tpj.13799). They are currently studying genetic variability in two A. thaliana populations. With one in France (TOU-A, n=195, 1.9M SNPs, LD 2kb, no population structure), they observe different genomic architectures for the response to monospecific and plurispecific interactions (https://www.biorxiv.org/content/10.1101/536953v1). They find candidate genes which are light-sensitive and also receptor-like kinases.

Increasing meiotic recombination in plants (Raphael Mercier, MPI Cologne, France)

After screening 6K mutant lines in A. thaliana they have discovered 3 pathways that limit crossover. His group has many papers published on this topic: https://scholar.google.com/citations?user=BKGJoo4AAAAJ . Some of his experiments involve rescuing mutant phenotypes with human proteins, which shows its degree of conservations. A remarkable example is the A. thaliana BRCA2 ortholog, which is involved in meiosis crossover control. His most recent work (see for instance https://www.pnas.org/content/115/10/2431.short) employs this knowledge to increase the frequency of crossover in plants without reducing fertility.