P-120 - Dissecting the pathogenicity mechanisms of the oomycete Phytophthora palmivora using genetic scissors

Phytophthora palmivora is one of the most destructive oomycete pathogens with a wide host range. Its genome encodes a large number of apoplastic and cytoplastic effectors, including over 700 RxLR effectors. P. palmivora is diploid with a whole genome duplication, leading to multi-copy genes. Due to this feature and low germination rate of oospores, its functional genomics study was impossible prior to the advent of CRISPR technology. By developing an efficient Agrobacterium-mediated transformation (AMT) and AMT-compatible CRISPR/Cas9 gene editing system, we have generated mutants of multiple effector proteins and determined their roles in pathogenicity, including the identification of a plant nuclear-localized RxLR effector as a key pathogenicity factor for infection of cacao. Identification and characterization of the DNA-binding activity and host targets of this effector, and the host cellular processes it modulates are underway. In addition, we have been optimizing the functional genomics tools for P. palmivora. We have recently developed a significantly simplified AMT protocol, which allows to transform P. palmivora with ease and higher level of reproducibility. As it is challenging to use the currently available CRISPR/Cas9 system for multiplex gene editing to study the functions of gene families or multi-copy genes with sequence variations, we have been establishing an AMT-compatible CRISPR/Cas12a gene editing system. Details will be presented in the meeting.