Understanding Mechanisms of Salinity Tolerance in Barley by Proteomic and Biochemical Analysis of Near-Isogenic Lines.

Juan Zhu,Rugen Xu,Sergey Shabala,Baojian Guo,Chengdao Li,Yun Fan,Chao Lv,Meixue Zhou

doi:10.3390/ijms21041516

Abstract

Salt stress is one of the major environmental factors impairing crop production. In our previous study, we identified a major QTL for salinity tolerance on chromosome 2H on barley (Hordeum vulgare L.). For further investigation of the mechanisms responsible for this QTL, two pairs of near-isogenic lines (NILs) differing in this QTL were developed. Sensitive NILs (N33 and N53) showed more severe damage after exposure to 300 mM NaCl than tolerant ones (T46 and T66). Both tolerant NILs maintained significantly lower Na+ content in leaves and much higher K+ content in the roots than sensitive lines under salt conditions, thus indicating the presence of a more optimal Na+/K+ ratio in plant tissues. Salinity stress caused significant accumulation of H2O2, MDA, and proline in salinity-sensitive NILs, and a greater enhancement in antioxidant enzymatic activities at one specific time or tissues in tolerant lines. One pair of NILs (N33 and T46) were used for proteomic studies using two-dimensional gel electrophoresis. A total of 53 and 51 differentially expressed proteins were identified through tandem mass spectrometry analysis in the leaves and roots, respectively. Proteins which are associated with photosynthesis, reactive oxygen species (ROS) scavenging, and ATP synthase were found to be specifically upregulated in the tolerant NIL. Proteins identified in this study can serve as a useful resource with which to explore novel candidate genes for salinity tolerance in barley.

Highlights

Soil salinity, one of the major abiotic stresses, has become a serious issue limiting agricultural production and threatening environmental health and economic welfare [1]
near-isogenic lines (NILs) offer unique advantages in physiological and genetic studies, since only two isolines are involved in assessing the effect of a particular allele, and the fixed genetic background avoids the noise from other genes [32]
Two pairs of NILs with contrasting salinity tolerance caused by an unique advantages in physiological and genetic studies, since only two isolines are involved in assessing the effect of a particular allele, and the fixed genetic background avoids the noise from other genes [32]

Summary

Introduction

One of the major abiotic stresses, has become a serious issue limiting agricultural production and threatening environmental health and economic welfare [1]. The response of plants to salinity stress presents complex quantitative traits that are affected by multiple environmental factors, involving complex physiological and molecular mechanisms [3]. Despite extensive and numerous studies having been conducted over the past few decades on the responses and mechanisms of salinity tolerance in plants, little progress has been made to date in developing high-yielding, salt-tolerant genotypes because of the genetic and physiological complexity of salinity tolerance [4] and a lack of reliable screening methods [5]. Osmotic stress and high accumulation of toxic Na+ in cytoplasm induce stomatal closure which causes a strong imbalance between light capture and energy utilization, reduces the photosynthetic rate, impairs the bioenergetic processes of photosynthesis, and leads to the formation of reactive oxygen species (ROS), such as superoxide radical (O2−), hydroxyl radical (OH), singlet oxygen (1O2), and hydrogen peroxide (H2O2) [6,7]. High respiration rates lead to excessive carbon being consumed by respiration, rather than in the synthesis of new tissue [13], and more ROS generation because of the overreduction of the electron transport in mitochondria [14]

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Conclusion