SlAGO4A, a core factor of RNA-directed DNA methylation (RdDM) pathway, plays an important role under salt and drought stress in tomato

• Published in: Molecular breeding Vol. 36; no. 3; pp. 1 - 13
• Main Authors: Huang, Wei, Xian, Zhiqiang, Hu, Guojian, Li, Zhengguo
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2016; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Biotechnology; Chlorophyll; Deoxyribonucleic acid; DNA; DNA methylation; DNA methyltransferase; Drought; Drought resistance; Gene expression; Genes; Genetic improvement; Germination; Life Sciences; Liquid oxygen; Molecular biology; Plant biology; Plant Genetics and Genomics; Plant Pathology; Plant Physiology; Plant Sciences; Proline; Ribonucleic acid; RNA; RNA-mediated interference; Salinity tolerance; Scavenging; Seed germination; Sugar; Transgenic plants; Argonaute (AGO); DNA methylation; Salt tolerance; Tomato; Drought tolerance
• ISSN: 1380-3743; 1572-9788
• DOI: 10.1007/s11032-016-0439-1

In Arabidopsis, it has been clarified that AGO4 protein is implicated in a phenomenon termed RNA-directed DNA methylation (RdDM). Previously, four orthologs of AtAGO4 were cloned in tomato, designated as SlAGO4A–SlAGO4D. Here, we studied the role of the SlAGO4A gene in regulating salt and drought tolerance in tomato. SlAGO4A-down-regulating (AS) transgenic tomato plants showed enhanced tolerance to salt and drought stress compared to wild-type (WT) and SlAGO4A-overexpressing (OE) transgenic plants, as assessed by physiological parameters such as seed germination rate, primary root length, chlorophyll/proline/MDA/soluble sugar/RWC content, and survival rate. Moreover, several genes involved in ROS scavenging and plant defense, including CAT, SOD, GST, POD, APX, LOX, and PR1, were up- or down-regulated consistently under salt and drought stress. Notably, expression levels of some DNA methyltransferase genes and RNAi pathway genes were significantly lower in AS plants than in WT. Taken together, our results suggest that SlAGO4A gene plays a negative role under salt and drought stress in tomato probably through the modulation of DNA methylation as well as the classical RNAi pathway. Hence, it may serve as a useful biotechnological tool for the genetic improvement of stress tolerance in crops.