Unveiling and exploiting Phytophthora capsici effectors and their host targets, with an emphasis on CRN effector proteins

摘要

Phytophthora capsici is a devastating plant pathogen for which virulence is aided by the secretion of effectors, including cytoplasmic effectors from the CRN (CRinkling and Necrosis) family. CRN effectors were first described in oomycetes by their capacity to induce host cell death. Nevertheless, despite recent efforts aiming to elucidate CRN virulence functions, the virulence relevance of CRN mediated cell death remains unknown. In this thesis, by performing a PCR based random mutagenesis screen on P. capsici CRN effector PcCRN83_152, we showed that PcCRN83_152 cell death is not required for its virulence function. In addition, we demonstrated that PcCRN83_152 interacts with nuclear proteins from the host plants N. benthamiana (NbSIZ1 and NbSLX1) and tomato (SlSIZ1∆867), which we connected to plant immunity processes and PcCRN83_152 mediated phenotypes. Besides increasing our knowledge on P. capsici CRN effectors, in this thesis we also aimed for the identification of new P. capsici effectors. Using a proteomics-based approach, we identified a set of candidate effectors from P. capsici that would not be identified using conventional genomic- and transcriptomic-based studies.In sum, in this thesis we summarise our current understanding of CRN effectors and re-assess some basic assumptions regarding this protein family. Moreover our results pointing to CRN virulence functions independent of cell death phenotypes provide a new conceptual framework for studies aimed at unveiling the virulence functions of cell death inducing CRNs. This knowledge complemented with the identification of PcCRN83_152 plant targets provides great leads to uncover PcCRN83_152 virulence functions. Moreover, the identification of new candidate effectors form P. capsici could be important towards a more global understanding of P. capsici virulence mechanisms.