The Dendrobium catenatum DcCIPK24 increases drought and salt tolerance of transgenic Arabidopsis

The CBL-interacting protein kinase (CIPK) protein plays a vital role in response to abotic stresses. Dendrobium catenatum has been listed as a rare and endangered plant in China because it is difficult for it to adapt suboptimal environmental stress. However, studies on its responses to abiotic stresses are rare. Herein, the CIPK24 gene was cloned from D. catenatum. Expression pattern analysis showed that it displayed a tissue-specificity with a relatively high expression level in sepal and petal, while its expression was up-regulated by polyethylene glycol (PEG) treatment in stems and leaves, and also by salt stress in roots. Localization analysis indicated that DcCIPK24 is located to the nucleus, plasma membrane and cytoplasm. DcCIPK24 overexpression increased the tolerance of transgenic Arabidopsis to drought and salt stresses when compare with wild-type (WT) plants. Transgenic plants had lower malondialdehyde (MDA) content, while had a higher proline content and superoxide dismutase (SOD) activity than WT plants under drought or salinity stress. Furthermore, drought treatment induced faster influxes of Ca2+ and H+ in transgenic roots compared with those in WT roots. Upon treatment with NaCl, Na+ efflux of the transgenic roots was faster, but K+ efflux rate was lower compared with those of WT roots, resulting in less Na+ accumulation in transgenic plants. RNA-seq analysis showed that 114 and 497 differentially expressed genes (DEGs) were found in DcCIPK24 transgenic plants under drought and salt stress, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses found that DEGs enriched in starch and sucrose metabolism, cutin and wax biosynthesis, and peroxisome pathway under drought stress, and enriched in phenylpropanoid biosynthesis pathway and mitogen-activated protein kinase (MAPK) signaling pathway under salt stress. These findings indicate that DcCIPK24 is a positive regulator of D. catenatum's response to drought and salt stresses, suggesting it has potential application in genetic modification of D. catenatum to enhance drought and salt tolerance.