Calcium-dependent protein kinase signalling in plant immune responses: current status and future prospects.

This review focuses on the critical role of CDPKs in advancing plant immunity research, highlighting how their functions can uncover key defence mechanisms and bridge critical knowledge gaps in the field. Calcium serves as the cornerstone of immune signalling, propagating pathogen-induced signals through specific sensors and decoders. Among these, calcium-dependent protein kinases (CDPKs) stand out as plant-specific signal transducers, directly converting calcium fluxes into defence activation. By modulating key immune components, CDPKs act as key hubs in plant immunity. Deciphering their role and crosstalks with other signalling networks is crucial for understanding the complexities of plant defence mechanisms. Although functional redundancy and extensive crosstalk among CDPK family members have historically hindered precise functional characterization, these features also highlight the robustness and adaptability of plant immune systems. Recent advances including high-throughput transcriptomics, comprehensive CDPK family-wide analyses, and multiplex genome-editing approaches such as CRISPR-Cas-based multi-gene targeting are now enabling finer functional resolution of CDPK members within complex multigene families. This review synthesizes current insights into CDPK-mediated signal transduction, with particular emphasis on their roles in coordinating defence responses and integrating with major signalling pathways, including mitogen-activated protein kinase (MAPK) cascades, reactive oxygen species (ROS) signalling, and WRKY transcription factor-mediated gene regulation. Importantly, the continued development of integrative and high-resolution approaches is poised to overcome longstanding limitations in the field, facilitating deeper dissection of CDPK-specific functions. Collectively, these advances position CDPK research at the forefront of plant immunity studies, with strong potential to reveal novel regulatory mechanisms.