Identification of Pseudoperonospora cubensis RxLR Effector Genes via Genome Sequencing.

Pseudoperonospora cubensis is a significant phytopathogen causing downy mildew disease in cucurbit crops. Understanding the molecular mechanisms underlying the interaction between P. cubensis and its host is essential for developing effective disease management strategies. RxLR effectors, secreted by pathogens, play a crucial role in modulating host immunity. In this study, we sequenced the genome of the P. cubensis isolate CNU-OTH and identified RxLR effector genes using bioinformatics tools. A total of 45 RxLR effector genes were identified from the genome of P. cubensis. Cloning and functional characterization of these effectors were performed through transient expression assays in Nicotiana benthamiana leaves. Subcellular localization of selected effectors was determined using GFP-tagged constructs. Functional characterization revealed that while most effectors did not induce a hypersensitive response (HR), a subset showed either weak or strong necrosis. Furthermore, several effectors demonstrated the ability to suppress cell death induced by BAX and INF1. Subcellular localization analysis indicated that RxLR effectors exhibited fluorescence in the nucleus and plasma membrane of N. benthamiana cells, suggesting diverse roles in host-pathogen interactions. This study provides insights into the genetic diversity and functional characterization of RxLR effectors in P. cubensis. Understanding the role of these effectors in manipulating host immunity is critical for developing strategies to combat downy mildew disease in cucurbit crops. The findings contribute to the broader understanding of plant-pathogen interactions and may facilitate the development of disease-resistant crop varieties.