Abstract:

Calmodulin kinase is a crucial component of calcium-binding proteins， which read and decode calcium signals and activate downstream target proteins to initiate stress responses in plants after stress stimulation. Reaumuria trigyna， a rare and uncommon salt-producing plant found only in east Alxa and west Ordos， is very resilient to environmental challenges including drought and salinity. Based on transcriptome information， the open reading frame （ORF） of RtCDPK16 was cloned in this study. The ORF shared 78.46% similarity with Arabidopsis thaliana and 80.97% identity with CDPK16 in Vitis vinifera， according to amino acid sequence alignment and evolutionary analyses. RtCDPK16 was found to be expressed in roots， stems， and leaves， with roots expressing it at the highest level. Stress conditions such as sodium chloride （NaCl）/macrogol （polyethylene glycol， PEG）/cold stress （cold）/abscisic acid （ABA） and other environmental stresses and calcium chloride （CaCl₂） were shown to greatly increase RtCDPK16 expression levels. Construction of plant expression vector and transformation of A. thaliana. Drought， salt and abscisic acid stress were applied to wild type Arabidopsis （WT） and overexpression Arabidopsis （OE） strains. The results showed that root length， fresh weight， chlorophyll content and other phenotypic indicators of OE strain were significantly higher than WT under stress treatment， indicating that the overexpression of RtCDPK16 made the transgenic strain obtain stronger stress tolerance. Physiological and biochemical indexes showed that， in each strain under stress treatment， the activities of antioxidant enzymes such as superoxide dismutase （SOD）， Peroxidase （POD）， catalase （CAT） and the content of osmotic regulators such as proline （Pro） and soluble sugar （SS） were significantly induced， and the OE strain was significantly higher than WT， while the accumulation of hydrogen peroxide （H₂O₂）/superoxide anion （O₂^-） was significantly lower than WT. Quantitative real-time （RT-PCR） detection found that the genes related to antioxidant enzymes， ABA synthesis and key elements of signal pathway， and proline synthesis genes of OE strains were significantly induced under stress. The above results indicate that the overexpression of RtCDPK16 in Arabidopsis can promote the osmotic balance and ROS （reactive oxygen species） homeostasis by regulating the genes expression of antioxidant enzyme and osmotic regulation in transgenic plants， and thus improve the stress tolerance of transgenic plants. This process may be achieved through ABA signal dependent approaches.

Key words: Reaumuria trigyna, abiotic stress, RtCDPK16, antioxidant, osmotic regulation