| Summary: | The most devastating abiotic factors worldwide are drought and salinity, causing severe bottlenecks in the agricultural sector. To acclimatize to these harsh ecological conditions, plants have developed complex molecular mechanisms involving diverse gene families. Among them, S-adenosyl-L-methionine synthetase (SAMS) genes initiate the physiological, morphological, and molecular changes to enable plants to adapt appropriately. We identified and characterized 16 upland cotton SAMS genes (<i>GhSAMSs</i>). Phylogenetic analysis classified the <i>GhSAMSs</i> into three major groups closely related to their homologs in soybean. Gene expression analysis under drought and salt stress conditions revealed that <i>GhSAMS2</i>, which has shown the highest interaction with <i>GhCBL10</i> (a key salt responsive gene), was the one that was most induced. <i>GhSAMS2</i> expression knockdown via virus-induced gene silencing (VGIS) enhanced transgenic plants’ susceptibility to drought and salt stress. The TRV2:<i>GhSAMS2</i> plants showed defects in terms of growth and physiological performances, including antioxidative processes, chlorophyll synthesis, and membrane permeability. Our findings provide insights into SAMS genes’ structure, classification, and role in abiotic stress response in upland cotton. Moreover, they show the potential of <i>GhSAMS2</i> for the targeted improvement of cotton plants’ tolerance to multiple abiotic stresses.
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