Overexpression of LcSABP, an Orthologous Gene for Salicylic Acid Binding Protein 2, Enhances Drought Stress Tolerance in Transgenic Tobacco.

Qian Li,Ting An,Chunfeng Guan,Yurong Wang,Jing Ji,Chao Jin,Gang Wang,Yue Zhang,Dan Yang

doi:10.3389/fpls.2019.00200

Abstract

Salicylic acid (SA) plays an essential role in the growth and development of plants, and in their response to abiotic stress. Previous studies have mostly focused on the effects of exogenously applied SA on the physiological response of plants to abiotic stresses; however, the underlying genetic mechanisms for the regulatory functions of endogenous SA in the defense response of plants remain unclear. In plants, SA binding protein 2 (SABP2), possessing methyl salicylate (MeSA) esterase activity, catalyzes the conversion of MeSA to SA. Herein, a SABP2-like gene, LcSABP, was cloned from Lycium chinense, which contained a complete open reading frame of 795 bp and encoded a protein of 264 amino acids that shared high sequence similarities with SABP2 orthologs from other plants. Overexpression of LcSABP enhanced the drought tolerance of transgenic tobacco plants. The results indicated that increased levels of LcSABP transcripts and endogenous SA content were involved in the enhanced drought tolerance. Physiological and biochemical studies further demonstrated that higher chlorophyll content, increased photosynthetic capacity, lower malondialdehyde content, and higher activities of superoxide dismutase, peroxidase, and catalase enhanced the drought tolerance of transgenic plants. Moreover, overexpression of LcSABP also increased the expression of reactive oxygen species (ROS)- and stress-responsive genes under drought stress. Overall, our results demonstrate that LcSABP plays a positive regulatory role in drought stress response by enhancing the endogenous SA content, promoting the scavenging of ROS, and regulating of the expression of stress-related transcription factor genes. Our findings indicate that LcSABP functions as a major regulator of the plant’s response to drought stress through a SA-dependent defense pathway.

Highlights

Abiotic stresses, such as drought and high salt stress, are thought to be the main factors adversely affecting plant growth and crop productivity, which limit global agricultural production (An et al, 2015; Wei T. et al, 2017)
The results indicated that increased levels of LcSABP transcripts and endogenous Salicylic acid (SA) content were involved in the enhanced drought tolerance
The results of multiple sequence alignment indicated that LcSABP shared high sequence identity with other SA binding protein 2 (SABP2) proteins from N. tabacum (NP_001312442.1, 88%), Capsicum baccatum (PHT55238.1, 84%), Solanum tuberosum (XP_006363634.1, 83%), Ipomoea nil (XP_019176400.1, 71%), Sesamum indicum (XP_011099228.1, 66%), Erythranthe guttata (XP_012852990.1, 67%), and Ziziphus jujuba (XP_015890093.1, 63%) (Figure 1A)

Summary

Introduction

Abiotic stresses, such as drought and high salt stress, are thought to be the main factors adversely affecting plant growth and crop productivity, which limit global agricultural production (An et al, 2015; Wei T. et al, 2017). SA is a naturally occurring phenolic compound and is one of the most important signaling molecules involved in the regulation of plant development, maturation, aging, and other physiological processes (Vlot et al, 2009; Klessig et al, 2018). It plays important roles in tolerance to abiotic stresses, such as those induced by salt, heat, and heavy metals (Kang et al, 2014). SA was shown to induce plants’ response to abiotic stress (Panda and Patra, 2007; Kang et al, 2012), most of the previous studies have focused on deciphering the mechanism of modulation of stress response by exogenous SA (Zhang et al, 2011), and the roles of endogenous SA remain poorly understood (Asensi-Fabado and Munné-Bosch, 2011; Miura et al, 2013)

Methods

Results

Conclusion