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.30>
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.
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