Silencing of GhSINAT5 Reduces Drought Resistance and Salt Tolerance in Cotton

The SEVEN IN ABSENTIA (SINA) E3 ubiquitin ligase is widely involved in drought and salt stress in plants. However, the biological function of the SINA proteins in cotton is still unknown. This study aimed to reveal the function of <i>GhSINAT5</i> through biochemical, genetic and molecular approaches. <i>GhSINAT5</i> is expressed in several tissues of cotton plants, including roots, stems, leaves and cotyledons, and its expression levels are significantly affected by polyethylene glycol, abscisic acid and sodium chloride. When <i>GhSINAT5</i> was silenced in cotton plants, drought and salinity stress occurred, and the length, area and volume of the roots significantly decreased. Under drought stress, the levels of proline, superoxide dismutase, peroxidase and catalase in the <i>GhSINAT5</i>-silenced cotton plants were significantly lower than those in the non-silenced control plants, whereas the levels of hydrogen peroxide and malondialdehyde were greater. Moreover, the expression of stress-related genes in silenced plants under drought stress suggested that <i>GhSINAT5</i> may play a positive role in the plant response to drought and salt stress by regulating these stress response-related genes. These findings not only deepen our understanding of the mechanisms of drought resistance in cotton but also provide potential targets for future improvements in crop stress resistance through genetic engineering.