6-SFT, a Protein from Leymus mollis, Positively Regulates Salinity Tolerance and Enhances Fructan Levels in Arabidopsis thaliana.

Mao Li,Xinhong Chen,Jixin Zhao,Jun Wu,Xiaolan He,Qunhui Yang,Dongdong Hao

doi:10.3390/ijms20112691

Abstract

Fructans play vital roles in abiotic stress tolerance in plants. In this study, we isolated the sucrose:6-fructosyltransferase gene, which is involved in the synthesis of fructans, from Leymus mollis by rapid amplification of cDNA ends. The Lm-6-SFT gene was introduced into Arabidopsis thaliana cv. Columbia by Agrobacterium-mediated transformation. The transgenic plants were evaluated under salt stress conditions. The results showed that the expression of Lm-6-SFT was significantly induced by light, abscisic acid (ABA), salicylic acid (SA), and salt treatment in L. mollis plants. Overexpression of Lm-6-SFT in Arabidopsis promoted seed germination and primary root growth during the early vegetative growth stage under salt stress. We also found that the transgenic plants expressing Lm-6-SFT had increased proline and fructan levels. β-Glucuronidase staining and promoter analysis indicated that the promoter of Lm-6-SFT was regulated by light, ABA, and salt stress. Quantitative PCR suggested that overexpression of Lm-6-SFT could improve salt tolerance by interacting with the expression of some salt stress tolerance genes. Thus, we demonstrated that the Lm-6-SFT gene is a candidate gene that potentially confers salt stress tolerance to plants. Our study will aid the elucidation of the regulatory mechanism of 6-SFT genes in herb plants.

Highlights

Abiotic stress, such as drought, low/high temperature, and soil salinity, has severe negative impact on plant growth and crop yield [1]
Gene structure analysis indicated that the Lm-6-SFT open reading frame (ORF) comprised 1866 bp and encoded a protein with 621 amino acids (Supplementary 1)
The cDNA for Lm-6-SFT was very similar to the 6-SFT genes from Psathyrostachys huashanica (NsNs) and Leymus racemosus (Lam.) Tzvel. (NsNsXmXm)

Summary

Introduction

Abiotic stress, such as drought, low/high temperature, and soil salinity, has severe negative impact on plant growth and crop yield [1]. Plants adapt to environmental stress by synthesizing stress-related substances such as proline and fructan. Soluble fructose is released to regulate the cellular osmotic pressure and stabilize cell membranes in plants [10,11]. Fructose plays important roles in enhancing the tolerance of plants to various types of abiotic stress [12,13,14]. Five types of fructans are found in plants, and these fructans are synthesized by four different fructosyltransferase (FT) enzymes [15,16]. In monocots, sucrose:fructan 6-fructosyltransferase (6-SFT) is a critical enzyme for fructan biosynthesis [17,18]. During the biosynthesis of fructans, 6-SFT could transfer a fructose unit to a fructan via a β(2,6) linkage [19,20]. Many types of 6-SFT genes have been identified in plant species such as wheat (Triticum aestivum) [21,22], barley (Hordeum vulgare), and oats (Avena sativa) [23]. 6-SFT genes have been used to generate transformed plants to test the functions of the genes [24,25,26]

Methods

Results

Conclusion