Abstract
Mitogen-activated protein kinases (MAPKs) activation is a common defense response of plants to a range of abiotic stressors. SlMPK3, 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 SlMPK3 from tomato and studied its role in cadmium (Cd2+) and drought tolerance. The results showed that transcripts of SlMAPK3 differentially accumulated in various plant tissues and were remarkably induced by different abiotic stressors and exogenous hormone treatments. Overexpression of SlMAPK3 increased tolerance to Cd2+ and drought as reflected by an increased germination rate and improved seedling growth. Furthermore, transgenic plants overexpressing SlMAPK3 showed an increased leaf chlorophyll content, root biomass accumulation and root activity under Cd2+ 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 SlMAPK3 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 SlMAPK3 gene in tomato positively regulates tolerance to Cd2+ and drought stress, which may have strengthen the molecular understanding of SlMAPK3 gene to improve abiotic stress tolerance.
Highlights
Plants are sessile living organisms, often exposed to diverse biotic and abiotic stress conditions throughout their life cycles
Tomato genome database showed that the SlMAPK3 gene is located on chromosome 6, encoding a protein of 373 amino acids having approximately 42.66 kDa molecular weight and an iso electric point
On the basis of phylogenetic analysis, they are divided into four groups and MAPK3 belongs to the group A having two other members of the family (Figure S1A)
Summary
Plants are sessile living organisms, often exposed to diverse biotic and abiotic stress conditions throughout their life cycles. MAPK cascades regulate many essential biological processes, including growth, development and programmed cell death (PCD) in plants [13]. These are three-tiered phospho-relay cascade consisting of MAPKK kinases that activate via phosphorylation of their downstream MAPKKs, which in turn further activate MAPKs [14]. Salicylic acid, and MAPK-related defense signaling pathways enhance resistance to bacterial wilt, and the induction of plant aminocyclopropane carboxylic acid oxidase (ACO) gene family occurs through MPK1-, 2, and 3 pathways following diethyl ether (ether) treatment [29,30]. Accumulation through the abscisic acid (ABA)-H2 O2 pathway to enhance drought tolerance in tomato and functions in Arabidopsis seed germination and seedling development during osmotic stress [34,35].
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