CBP60g Positively Regulates The Responses Of Arabidopsis Thaliana To Pseudomonas Syringae,Abscisic Acid And Drought

Calmodulin-binding proteins (CBPs) have been known to be involved in both biotic and abiotic stress responses. Recently, two closely related CBPs, Arabidopsis thaliana SAR Deficient1(SARD1) and CBP60g, were found to belong to a new family of transcription factors that regulate salicylic acid (SA) biosynthesis triggered by microbe-associated molecular patterns (MAMPs). However, it is still unknown whether overexpression of CBP60g affects Arabidopsis resistance to disease and other aspects.In this study, we generated CBP60g overexpression lines and investigate the function of CBP60g in disease resistance, abscisic acid (ABA) response and drought tolerance in Aarabidopsis.We found that overexpression of CBP60g in Arabidopsis caused SA accumulation, increased pathogenesis-related (PR) genes expression and enhanced resistance to Pseudomonas syringae infection. Interestingly, the CBP60g overexpression lines showed hypersensitivity to ABA inhibited cotyledon greening and primary root growth, and more tolerant to drought. Expression assay showed that CBP60g was ubiquitously expressed and localized to nuclei. We also found that treatment with ABA and drought stress lead to a higher expression level of the ICS1gene, which encodes isochorismate synthase, in the CBP60g overexpression lines than in the wild-type plants. Additionally, application of SA enhances the root growth inhibition effect of ABA to wild type Arabidopsis, while crossing NahG transgenic plants with CBP60g overexpression lines abolished its ABA hypersensitivity.Our results suggest that CBP60g is not only involved in biotic stress but also abiotic stress, and serves as a molecular link that positively regulates ABA-and SA-mediated pathways in plants.