A plant-specific calmodulin-binding protein, AtCBP60b, mediates Ca2+ dynamics and signaling responses and is critical...

Calcium (Ca2+) is an essential mineral nutrient and a vital signaling molecule for plant growth and development. Ca2+/calmodulins (CaMs) can bind proteins, called CaM-binding proteins (CBPs), to relay Ca2+ signals and modulate transcriptional activity. In this study, we demonstrate that AtCBP60b, a member of the CBP60 family, is an essential factor in regulating plant growth and development. AtCBP60b loss-of-function plants showed impaired seedling growth, leaf development, and plant structural architecture under normal growth conditions. Transcriptomic profiles indicated a central role for AtCBP60b in the transcriptional regulation of the Ca2+ signaling pathway, growth homeostasis, and immune and stress responses. Disruption of AtCBP60b leads to Ca2+ deficiency hypersensitivity and altered regulation of Ca2+ dynamics and Ca2+ signaling responses. AtCBP60b was found to bind CaM which was determined to be required for AtCBP60b function in transcriptional regulation of the genes encoding the pathways maintaining cytosolic Ca2+ homeostasis, regulating defense, growth, and development. In addition, we show that elevated temperatures can rescue the atcpb60b growth and development defects through reprogramming of the transcriptional profiles of the genes regulating these processes. Overall, our findings demonstrate that AtCBP60b plays an important role in regulating plant Ca2+ signaling response, growth and development, and responses to elevated temperature.