Genome-Wide Analysis and Cloning of the Apple Stress-Associated Protein Gene Family Reveals MdSAP15, Which Confers Tolerance to Drought and Osmotic Stresses in Transgenic Arabidopsis

Qinglong Dong,Fengwang Ma,Bingyao Xu,Qian Wang,Chao Li,Dingyue Duan,Xiaoqing Gong,Changhai Liu,Jiawei Luo,Dong Huang,Shuang Zhao,Ke Mao

doi:10.3390/ijms19092478

Abstract

Stress-associated proteins (SAPs) are novel A20/AN1 zinc finger domain-containing proteins that are now favorable targets to improve abiotic stress tolerance in plants. However, the SAP gene family and their biological functions have not been identified in the important fruit crop apple (Malus × domestica Borkh.). We conducted a genome-wide analysis and cloning of this gene family in apple and determined that the overexpression of MdSAP15 enhances drought tolerance in Arabidopsis plants. We identified 30 SAP genes in the apple genome. Phylogenetic analysis revealed two major groups within that family. Results from sequence alignments and analyses of 3D structures, phylogenetics, genomics structure, and conserved domains indicated that apple SAPs are highly and structurally conserved. Comprehensive qRT-PCR analysis found various expression patterns for MdSAPs in different tissues and in response to a water deficit. A transgenic analysis showed that the overexpression of MdSAP15 in transgenic Arabidopsis plants markedly enhanced their tolerance to osmotic and drought stresses. Our results demonstrate that the SAP genes are highly conserved in plant species, and that MdSAP15 can be used as a target gene in genetic engineering approaches to improve drought tolerance.

Highlights

The growth, development, and survival of plants is constantly challenged by a variety of biotic and abiotic environmental factors
MDA concentrations did not differ among genotypes under normal conditions, but were lower in the overexpressed (OE) lines than in the WT following mannitol treatment (Figure 7H). These results suggested that the overexpression of MdSAP15 in Arabidopsis seedlings leads to enhanced osmotic stress tolerance
Sequencing of its genome has provided a good platform for genome-wide analyses of all putative gene families in apple, including the DREB [29], MYB [30], MADS-box [31], and WRKY [32,33] families

Summary

Introduction

The growth, development, and survival of plants is constantly challenged by a variety of biotic and abiotic environmental factors. Some key modulators of stress responses have been characterized and have emerged as appropriate targets to enhance abiotic stress tolerance in many plants. They include NAC domain-containing transcription factors, DRE/CRT-binding transcription factors (DREBs/CBFs), mitogen-activated protein kinases (MAPKs), stress-associated proteins (SAPs), and heat shock factor/proteins (HSPs/HSF) [1,3,4,5,6]. The SAPs are a newly identified class of zinc finger proteins (ZFPs) that play crucial roles in various abiotic stress responses by numerous plants [1,2,7]. One significant feature of plant SAPs is the very frequent occurrence of intronless genes [2]. 11 rice SAP genes, 15 from desert poplar (Populus euphratica), and 30 from cotton lack introns and show a remarkably higher percentage of intronless genes [2,6,11]

Methods

Results

Conclusion