CBL-Interacting protein kinase 21 (CIPK21) negatively regulates plant immune responses during Pseudomonas syringae infection

Title : CBL-Interacting protein kinase 21 (CIPK21) negatively regulates plant immune responses during Pseudomonas syringae infection

Abstract:

Pathogen response requires a rapid and sustained increase in cytosolic calcium (Ca²⁺) levels. Calcineurin B-like (CBL)-interacting protein kinases (CIPKs) are downstream messenger of Ca²⁺-signature which regulate various physiological processes in plants. So, we characterized CIPK21 in plant-pathogen interaction response which is mediated through the salicylic acid pathway. We observed that the cipk21 mutant was more resistant to P. syringae than Col-0, whereas its complementation and overexpression lines showed susceptibility. Histochemical analysis revealed that cipk21 leaves accumulated significantly more H₂O₂ and callose deposition than Col-0 leaves. These results corroborated the expression of pathogenesis-related (PR1/2) and P. syringae-induced SA signaling (ICS1) genes, ROS production and callose deposition. Moreover, we identified CBL9 as an upstream interactor and the dual specificity phosphatase-4 (DSP4) as the downstream interactor of CIPK21. DSP4-CIPK21 interaction was confirmed through Y2H and BiFC assays. The dsp4 mutant was susceptible to P. syringae infection indicating the regulation of biotic stress responses. Ca²⁺-dependent successive phosphorylation of DSP4 by CBL9-CIPK21 is critical during plant-pathogen interaction. DSP4 is responsible for starch metabolism. The Ca²⁺-CBL9-CIPK21-DSP4 interactions will be greatly beneficial in understanding the molecular machinery involved downstream of Ca²⁺ in decoding the biotic stress signal and help in crop improvement.

Biography:

Amit Kumar is a research scholar pursuing his Ph.D. in Plant Molecular Biology at the University of Delhi, with special emphasis on deciphering the role of calcium signaling components (kinases) and their downstream during combined stress of nutrition stress signaling and biotic stress response in plants. He completed his M.Sc in Botany from the Department of Botany, University of Delhi (2016-2018), and graduated with honours in Botany from Hansraj College, University of Delhi (2013-2016). With a strong academic foundation in plant sciences, Amit's research interests lie in understanding the molecular mechanisms underlying plant biology. His academic journey reflects his passion for botany and commitment to advancing knowledge in the field.