A calcium sensor calcineurin B-like 9 negatively regulates cold tolerance via calcium signaling in Arabidopsis thaliana

摘要

6 Calcineurin B-like protein 9 (CBL9) plays important roles in response to ABA, K+ deprivation in plants. However, whether CBL9 modulates plant adaptation to low-temperature stress is elusive. In this study, we demonstrated that the cbl9 mutants increased freezing tolerance under both cold-acclimating and nonacclimating conditions in Arabidopsis. Cold-induced changes of cytosolic free calcium concentration ([Ca2+](cyt)) were then monitored by aequorin-expressed Arabidopsis plants. The results showed that the cold-triggered increases in [Ca2+](cyt) levels in cbl9 mutants were clearly higher than those in wild type (WT) plants, while cold-affected changes in free calcium concentration within cytosolic microdomains adjacent to the vacuolar membrane ([Ca2+](md)) in cbl9 mutants were similar to those in WT plants. In addition, treatments of seedlings with Ca2+ chelator ethylene glycol-bis(2-aminoethylether)-N,N,N ',N '-tetraacetic acid (EGTA) and Ca2+ channel blocker lanthanum chloride markedly inhibit changes of [Ca2+](cyt) in cbl9 mutants, while the inhibition of calcium release by lithium chloride from intracellular pools demonstrated consistent suppression of [Ca2+](cyt) in cbl9 mutants and WT plants. Together, these results indicate that CBL9 negatively modulates cold tolerance through decreasing [Ca2+](cyt) in Arabidopsis.