The Functional and Regulatory Mechanisms of the Thellungiella salsuginea Ascorbate Peroxidase 6 (TsAPX6) in Response to Salinity and Water Deficit Stresses.

Zeqin Li,Genfa Zhang,Hongjie Li,Jilong Zhang,Jingxiao Li,Hong Zhang

doi:10.1371/journal.pone.0154042

Zeqin Li, Genfa Zhang + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0154042

Copy DOI

Abstract

Soil salinization is a resource and ecological problem in the world. Thellungiella salsuginea is becoming a new model plant because it resembles its relative species, Arabidopsis thaliana, in small genome and short life cycle. It is highly tolerant to salinity and drought stresses. Ascorbate peroxidase (APX) is an enzyme that clears H2O2 in plants. The function and molecular and regulation mechanisms of APX in T. salsuginea have rarely been reported. In this study, an APX gene, TsApx6, was cloned from T. salsuginea and its responses to abiotic stresses in transgenic Arabidopsis were studied. Under high salinity treatment, the expression of TsApx6 was significantly induced. Under drought treatment, overexpression of TsApx6 increased the survival rate and reduced leaf water loss rate in Arabidopsis. Compared to the wild type plants, high salinity treatment reduced the concentrations of MDA, H2O2 and proline but elevated the activities of APX, GPX, CAT and SOD in the TsApx6-overexpressing plants. Meanwhile, germination rate, cotyledon greening, and root length were improved in the transgenic plants compared to the wild type plants under salt and water deficit conditions. Based on these findings, TsApx6 has an important function in the resistance of plants to certain abiotic stresses. The TsApx6 promoter sequence was obtained using Genome Walking technology. Bioinformatics analysis indicated that it contains some cis-acting elements related to stress response. The treatments of salt, dehydration, and ABA induced the expression of Gus gene under the regulation of the TsApx6 promoter. Mutation analysis showed that the MBS motif present in the TsApx6 promoter might be a key negative regulatory element which has an important effect on the growth and developmental process of plants.

Highlights

The life cycle of a plant is influenced by various environmental factors
The activities of all the antioxidant enzymes in transgenic lines, especially 35S:TsApx6-GFP, were prominently greater than those in the atapx6 mutant and the WT (P < 0.01). These findings strongly indicated that the expression of TsApx6 in Arabidopsis resulted in the coordinated increase of antioxidant enzyme activities under the conditions of salt stress, which provided a common protection for plants against oxidative damage
The present study focused on an ascorbate peroxidase, which is located in cytoplasm and has important function in the physiological and metabolism systems in T. salsuginea

Summary

Introduction

The life cycle of a plant is influenced by various environmental factors. Drought and salinity are important in reducing plant productivity and limiting plant distribution. Plants have a large network for ROS production and scavenging in various cellular compartments that are essential for regulating ROS signals in the growth, development, and defense against environmental stresses. In Arabidopsis thaliana L., such a network consists of at least 152 genes encoding ROS producing proteins, including nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and ROS removing enzymes. This class of enzymes includes ascorbate peroxidases (APX, EC 1.11.1.1), glutathione peroxidase (GPX, EC 1.11.1.9), catalase (CAT, EC 1.11.1.6) and superoxide dismutases (SOD, EC 1.15.1.1) [8,9,10,11]. Ascorbate peroxidases with the strongest affinity for H2O2 are central components of the H2O2 scavenging networks and very important in the regulation of cellular ROS levels [12]

Methods

Results

Conclusion