[Cloning and functional analysis of SiLTP3 gene in drought resistance and salt tolerance in Setaria italica].

To investigate the function of SiLTP3, a member of the nsLTPfamily in Setaria italica (foxtail millet), in drought resistance and salt tolerance, sequence analysis of SiLTP3 was performed, and its coding sequence was cloned and overexpressed in Nicotiana benthamiana. By comparing the morphological and physiological responses of the SiLTP3-overexpressing line (SiLTP3-OE) and wild-type plant under drought stress (25% PEG-6000) and salt stress (400 mmol/LNaCl), the drought resistance and salt tolerance function of SiLTP3 was validated, and the mechanisms underlying its response to drought and salt stress were preliminarily explored. The results showed that the SiLTP3 protein is a hydrophobic secretory protein with the conserved nsLTP1 domain, is phylogenetically closely related to Phragmites australis PaLTP1 and PaLTP3, and harbors serine (Ser) and threonine (Thr) phosphorylation sites. The introduction of SiLTP3 significantly reduced the water loss rate of detached tobacco leaves and improved their water retention capacity. Overexpression of SiLTP3 could significantly reduce the wilting index and increase the shoot fresh weight and leaf surface area of tobacco plants under drought and salt stress. Meanwhile, overexpression of SiLTP3 could maintain higher chlorophyll content, higher peroxidase and superoxide dismutase activities, and lower relative electrolyte leakage and malondialdehyde content. In summary, overexpression of SiLTP3 significantly enhanced drought resistance and salt tolerance of the tobacco plants, and SiLTP3 may alleviate drought- and salt-stress-induced damage to cell membranes and photosynthetic apparatus by enhancing the antioxidant capacity of tobacco, thereby improving drought resistance and salt tolerance.