The NAC Protein from Tamarix hispida, ThNAC7, Confers Salt and Osmotic Stress Tolerance by Increasing Reactive Oxygen Species Scavenging Capability

Abstract

Plant specific NAC (NAM, ATAF1/2 and CUC2) transcription factors (TFs) play important roles in response to abiotic stress. In this study, we identified and characterized a NAC protein, ThNAC7, from <i>Tamarix hispida</i>. <i>ThNAC7</i> is a nuclear localized protein and has transcriptional activation activity. <i>ThNAC7</i> expression was markedly induced by salt and osmotic stresses. Transiently transformed <i>T. hispida</i> seedlings overexpressing <i>ThNAC7</i> (OE) or with RNA interference (RNAi) silenced <i>ThNAC7</i> were generated to investigate abiotic stress tolerance via the gain- and loss- of function. Overexpressing <i>ThNAC7</i> showed an increased reactive oxygen species (ROS) scavenging capabilities and proline content, which was accomplished by enhancing the activities of superoxide dismutase (SOD) and peroxidase (POD) in transiently transformed <i>T. hispida</i> and stably transformed <i>Arabidopsis</i> plants. Additionally, <i>ThNAC7</i> activated these physiological changes by regulating the transcription level of <i>P5CS</i>, <i>SOD</i> and <i>POD</i> <i>genes</i>. RNA-sequencing (RNA-seq) comparison between wild-type and <i>ThNAC7</i>-transformed <i>Arabidopsis</i> showed that more than 40 known salt tolerance genes might regulated by <i>ThNAC7</i>, including stress tolerance-related genes and TF genes. The results indicated that <i>ThNAC7</i> induces the transcription level of genes associated with stress tolerance to enhance salt and osmotic stress tolerance via an increase in osmotic potential and enhanced ROS scavenging.