Overexpression of a Mitogen-Activated Protein Kinase Positively Regulates Tomato Tolerance to Cadmium and Drought Stress.

Mitogen-activated protein kinases (MAPKs) activation is a common defense response of plants to a range of abiotic stressors. , a serine-threonine protein kinase, has been reported as an important member of protein kinase cascade that also functions on plant stress tolerance. In this study, we cloned from tomato and studied its role in cadmium (Cd) and drought tolerance. The results showed that transcripts of differentially accumulated in various plant tissues and were remarkably induced by different abiotic stressors and exogenous hormone treatments. Overexpression of increased tolerance to Cd and drought as reflected by an increased germination rate and improved seedling growth. Furthermore, transgenic plants overexpressing showed an increased leaf chlorophyll content, root biomass accumulation and root activity under Cd stress. Chlorophyll fluorescence analysis revealed that transgenic plants demonstrated an increased photosynthetic activity as well as contents of chlorophyll, proline, and sugar under drought stress. Notably, cadmium- and drought-induced oxidative stress was substantially attenuated in overexpressing plants as evidenced by lower malondialdehyde and hydrogen peroxide accumulation, and increased activity and transcript abundance of enzymatic antioxidants under stress conditions compared to that of wild-type. Our findings provide solid evidence that overexpression of gene in tomato positively regulates tolerance to Cd and drought stress, which may have strengthen the molecular understanding of gene to improve abiotic stress tolerance.