Genome-wide identification and functional characterization of RxLR effectors in Phytophthora cinnamomi infecting Carya cathayensis Sarg

Phytophthora cinnamomi is a globally distributed oomycete pathogen capable of infecting over 5,000 plant species, causing devastating root rot and stem canker diseases with significant agricultural and ecological impacts. Similar to other Phytophthora species, P. cinnamomi secretes RxLR effectors to suppress host immunity and facilitate infection. Here, we present a high-quality genome assembly of P. cinnamomi strain ST402 isolated from an economically important Chinese hickory (Carya cathayensis Sarg.), revealing 146 putative RxLR effectors. Transcriptomic profiling during the early infection stages (0–36 h post-inoculation) identified 66 differentially expressed RxLR effectors, with 4 highly induced candidates (PciRxLR1, PciRxLR21, PciRxLR57, and PciRxLR69) demonstrating cell death suppression activity against pathogen-associated molecular patterns (PAMPs) and promoting Phytophthora pathogenicity in Nicotiana benthamiana. Subcellular localization revealed distinct nuclear and cytoplasmic targeting patterns of these effectors. Our findings provide critical insights into the molecular mechanisms underlying P. cinnamomi virulence and lay the foundation for developing targeted control strategies against this destructive pathogen.