Dissecting the molecular mechanisms of cellular heterogeneity controlling infection-associated development in plant pathogenic fungi

Clonal microorganisms display cellular heterogeneity at the transcriptional level, to survive under unfavourable conditions or differentiate into specialised structures. This is the basis of antibiotic and fungicide resistance, but very little is known about how cellular heterogeneity originates and operates in the infection biology of agricultural fungi. Magnaporthe oryzae is one of the most devastating fungal pathogens in the world that destroys enough rice to feed 60M people every year. It produces ~50,000 new spores a day from a single lesion in the fields, but it remains unknown whether they are transcriptionally different. Spores contain three cells that display cellular heterogeneity between them during appressorium development, a specialised cell necessary for infection. Two of the cells undergo autophagy rapidly and the third undergoes a mitotic division leading to the formation of the appressorium. The mechanism by which cellular heterogeneity operates in spores has never been elucidated. This proposal will identify, for the first time, the molecular mechanisms driving cellular heterogeneity and genes subjected to it. An unparalleled resolution of the infection-associated developmental program of individual spore cells will be obtained by scRNA-seq, which will identify a cohort of virulence factors critical for infection. I propose that the underlying mechanism of cellular heterogeneity is the cell cycle, through the activity of Cyclin Dependent Kinases CDKs and a novel group called non-PSTARE CDKs, reported to be regulators of transcription in other organisms. By a state-of-the-art chemical genetic approach combined with phosphoproteomics, their role and signalling pathways will be determined. Overall, with this proposal, novel components associated to the infection process of one of the most threatening fungal pathogens in the world will be determined, opening avenues that up to date have not been explored and whose potential is inestimable.

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