ALT1, a Snf2 family chromatin remodeling ATPase, negatively regulates alkaline tolerance through enhanced defense against oxidative stress in rice.

Mingxin Guo,Xiaoqiang Liu,Kai Hua,Ruci Wang,Shanguo Yao,Juan Wang,Yueming Wang,Ji-Hong Liu

doi:10.1371/journal.pone.0112515

Abstract

Alkaline salt stress adversely affects rice growth, productivity and grain quality. However, the mechanism underlying this process remains elusive. We characterized here an alkaline tolerant mutant, alt1 in rice. Map-based cloning revealed that alt1 harbors a mutation in a chromatin remodeling ATPase gene. ALT1-RNAi transgenic plants under different genetic background mimicked the alt1 phenotype, exhibiting tolerance to alkaline stress in a transcript dosage-dependent manner. The predicted ALT1 protein belonged to the Ris1 subgroup of the Snf2 family and was localized in the nucleus, and transcription of ALT1 was transiently suppressed after alkaline treatment. Although the absorption of several metal ions maintained well in the mutant under alkaline stress, expression level of the genes involved in metal ions homeostasis was not altered in the alt1 mutant. Classification of differentially expressed abiotic stress related genes, as revealed by microarray analysis, found that the majority (50/78) were involved in ROS production, ROS scavenging, and DNA repair. This finding was further confirmed by that alt1 exhibited lower levels of H2O2 under alkaline stress and tolerance to methyl viologen treatment. Taken together, these results suggest that ALT1 negatively functions in alkaline tolerance mainly through the defense against oxidative damage, and provide a potential two-step strategy for improving the tolerance of rice plants to alkaline stress.

Highlights

The widely distributed salt and alkaline salts are important abiotic stress factors that greatly affect plant growth and development and severely threat crop productivity throughout the world [1]
From a total of 100,000 M2 individuals treated with NaHCO3-NaOH solution, we identified a mutant, alt1 with enhanced tolerance to alkaline stress
The common feature for plants grown in calcareous soils is chlorosis, a typical symptom of Fe deficiency

Summary

Introduction

The widely distributed salt and alkaline salts are important abiotic stress factors that greatly affect plant growth and development and severely threat crop productivity throughout the world [1]. Few regulators have been identified to function directly in the tolerance of plants to alkaline salt stress. Various groups have sought to genetically engineer crop plants with improved Fe uptake under alkaline salt conditions, by introducing genes encoding iron transporters, iron reductases, and enzymes involved in phytosiderophore biosynthesis into plants [8,9,10,11,12,13,14]. Ectopic expression of the yeast Fe3+-chelate-reductase gene refre1/372 greatly improved grain yield on calcareous soil-grown rice plants [9]

Methods

Results

Conclusion