ThNAC13, a NAC Transcription Factor from Tamarix hispida, Confers Salt and Osmotic Stress Tolerance to Transgenic Tamarix and Arabidopsis

Abstract

NAC (NAM, ATAF1/2, and CUC2) proteins play critical roles in many plant biological processes and environmental stress. However, NAC proteins from <i>Tamarix hispida</i> have not been functionally characterized. Here, we studied a <i>NAC</i> gene from <i>T</i>. <i>hispida, ThNAC13</i>, in response to salt and osmotic stresses. ThNAC13 is a nuclear protein with a C-terminal transactivation domain. ThNAC13 can bind to NAC recognized sites and calmodulin-binding NAC (CBNAC) binding element. Overexpression of <i>ThNAC13</i> in <i>Arabidopsis</i> improved seed germination rate and increased root growth and fresh weight gain under salt or osmotic stress. Transgenic <i>T</i>. <i>hispida</i> plants transiently overexpressing <i>ThNAC13</i> and with RNAi-silenced <i>ThNAC13</i> were generated for gain- and loss-of-function experiments. Following exposure to salt or osmotic stress, overexpression of <i>ThNAC13</i> induced superoxide dismutase (SOD) and peroxidase (POD) activities, chlorophyll and proline contents; decreased the reactive oxygen species (ROS) and malondialdehyde levels; and reduced electrolyte leakage rates in both transgenic <i>Tamarix</i> and <i>Arabidopsis</i> plants. In contrast, RNAi-silenced <i>ThNAC13</i> showed the opposite results in transgenic <i>Tamarix</i>. Furthermore, <i>ThNAC13</i> induced the expression of <i>SOD</i>s and <i>POD</i>s in transgenic <i>Arabidopsis</i>. These results suggest that ThNAC13 improves salt and osmotic tolerance by enhancing the ROS-scavenging capability and adjusting osmotic potential.