Overexpression of plant polyketide synthase AsPECPS from Aquilaria sinensis enhances the tolerance of the transgenic Nicotiana benthamiana to salt stress and ABA treatment

Type III polyketide synthases play significant roles in the biosynthesis of multiple plant secondary metabolites and plant adjustment to environmental stresses. AsPECPS , a type III polyketide synthase, is the key enzyme involved in the biosynthesis of 2-(2-phenylethyl) chromone derivatives which are the main components determining the quality of agarwood and special defensive substances of Aquilaria sinensis . However, the functions of AsPECPS in plant resistance have not been shown. Our findings indicated that AsPECPS was localized in the cytoplasm and cell wall. The expression of AsPECPS was significantly induced by salt stress and abscisic acid (ABA) treatment. Heterologous overexpression of AsPECPS in Nicotiana benthamiana enhanced the salt-stress tolerance at post-gemination stage showed by the transgenic plants with increased fresh weight, height, root length, and number of lateral roots. Furthermore, the overexpressing lines (OE) in soil retained more lateral roots, more proline content and lower malondialdehyde content under salinity stress. Additionally, AsPECPS -OE plants were less sensitive to ABA as indicated through the OE lines showing higher gemination rate, greater survival rate, and better growth characteristics. Further analyses demonstrated that the transgenic plants accumulated lower levels of ROS through down-regulating the expression of Rboh family genes and up-regulating the expression and activities of antioxidant enzymes under salt stress and ABA treatment. Overexpression of AsPECPS modulated the abundance of genes associated with ABA signaling pathway under ABA treatment. Taken together, our results indicated that overexpression of AsPECPS in N. benthamiana enhanced the plant tolerance to salt and ABA stresses. Key Message Overexpression of AsPECPS in N. benthamiana , a type III polyketide synthase involved in the biosynthesis of 2-(2-phenylethyl) chromone, enhanced the plant tolerance to salt and ABA stresses. Graphical abstract