Overexpression of isochorismate synthase enhances drought tolerance in barley

Isochorismate synthase (ICS) is a key enzyme for the synthesis of salicylic acid (SA) in plants. SA mediates plant responses to both biotic and abiotic stresses. In previous studies, we found that overexpression of ICS (ICS_OE) or suppression of ICS (ICS_RNAi) affected the host response to Fusarium graminearum in barley. However, whether the barley ICS gene plays a role in adapting to abiotic stresses remains to be determined. In the present study, expression of the ICS gene was upregulated when treated with 20 % PEG6000, and ICS_OE lines were more drought tolerant than wild type (WT) and ICS_RNAi. In addition, the abscisic acid (ABA) levels in the ICS_OE lines were higher than those in the WT and ICS_RNAi lines under drought stress. High ABA levels significantly reduced Gs and E, which may impact water retention under drought stress. Under drought conditions, the activity of antioxidant enzymes was significantly higher in the ICS_OE lines, correlating with a lower levels of reactive oxygen species (ROS) and malondialdehyde (MDA). Enhanced antioxidant competence also contributed to drought tolerance in ICS_OE lines. These findings help elucidate the abiotic stress resistance of the ICS pathway in barley.