Saranya Vijayakumar Manjula Sakuntala ^*

• Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India

The devastating disease 'quick wilt' or 'foot rot' is caused by the oomycete Phytophthora capsici Leonian and is affecting the economically significant spice crop black pepper (Piper nigrum L.). is caused by the oomycete Phytophthora capsici Leonian. The details on the mechanism of interaction of P. capsici and with its host black pepper P. nigrum remain poorly understood, hindering efforts to enhance disease resistance. To address this knowledge gap, we conducted an RNA-seq analysis to investigate the gene expression profile of P. capsici while infecting P. nigrumblack pepper. Comparative transcriptome analysis between axenic culture, and early and late infection stages of P. capsici revealed a substantial number of differentially expressed genes. Our findings demonstrate the induction of metabolic pathways, signaling cascades, and crucial pathogenicity-related processes during infection of black pepperP. nigrum by P. capsici. Specifically, we observed orchestrated expression of cell wall-degrading enzymes, effectors, and, detoxifying transporters at different infection time points, implicating their roles in pathogenicity. The expression patterns of key pathogenicity-associated genes, including effectors, were validated using reverse transcription quantitative real-time PCR. The effectiveness of agroinfiltration-mediated transient expression in black pepperP. nigrum for functional studies of effectors is also demonstrated in this study. Overall, this study establishes a strong foundation for further studies elucidating the pathogenic mechanisms employed by P. capsici during infecting black pepperP. nigrum and for developing effective disease