Transcriptional regulation of heat shock proteins and ascorbate peroxidase by CtHsfA2b from African bermudagrass conferring heat tolerance in Arabidopsis.

Xiuyun Wang,Bingru Huang,Jun Liu,Wanlu Huang,Zhimin Yang

doi:10.1038/srep28021

Abstract

Heat stress transcription factor A2s (HsfA2s) are key regulators in plant response to high temperature. Our objectives were to isolate an HsfA2 gene (CtHsfA2b) from a warm-season grass species, African bermudagrass (Cynodon transvaalensis Burtt-Davy), and to determine the physiological functions and transcriptional regulation of HsfA2 for improving heat tolerance. Gene expression analysis revealed that CtHsfA2b was heat-inducible and exhibited rapid response to increasing temperature. Ectopic expression of CtHsfA2b improved heat tolerance in Arabidopsis and restored heat-sensitive defects of Arabidopsis hsfa2 mutant, which was demonstrated by higher survival rate and photosynthetic parameters, and lower electrolyte leakage in transgenic plants compared to the WT or hsfa2 mutant. CtHsfA2b transgenic plants showed elevated transcriptional regulation of several downstream genes, including those encoding ascorbate peroxidase (AtApx2) and heat shock proteins [AtHsp18.1-CI, AtHsp22.0-ER, AtHsp25.3-P and AtHsp26.5-P(r), AtHsp70b and AtHsp101-3]. CtHsfA2b was found to bind to the heat shock element (HSE) on the promoter of AtApx2 and enhanced transcriptional activity of AtApx2. These results suggested that CtHsfA2b could play positive roles in heat protection by up-regulating antioxidant defense and chaperoning mechanisms. CtHsfA2b has the potential to be used as a candidate gene to genetically modify cool-season species for improving heat tolerance.

Highlights

Temperatures above the normal optimum, sensed as heat stress (HS), are main environmental adverse factors for terrestrial plants limiting their growth, yield and distribution worldwide
QRT-PCR analysis demonstrated that CtHsfA2b exhibited rapid response to heat stress (Fig. 1c), as the expression level increased within 30 min and reached the highest level by 1 h of 42 °C heat treatment in leaves and roots of African bermudagrass
CtHsfA2b was rapidly up-regulated within 1 h of 42 °C heat treatment and transcripts of CtHsfA2b attenuated quickly when plants were exposed to the normal temperature and remained at low levels during the recovery phase

Summary

Introduction

Temperatures above the normal optimum, sensed as heat stress (HS), are main environmental adverse factors for terrestrial plants limiting their growth, yield and distribution worldwide. The objectives of the study were to isolate an HsfA2 gene (CtHsfA2b) from a heat-tolerant warm-season perennial grass species, African bermudagrass (Cynodon transvaalensis Burtt-Davy), and to determine the physiological functions and transcriptional regulation of CtHsfA2b on downstream target genes conferring heat tolerance in the model species, Arabidopsis. To our knowledge, this is the first study reporting the roles of HsfA2b cloned from a warm-season perennial grass species in improving plant heat tolerance through transcriptional upregulation of a chaperoning and antioxidant-defense gene in improving plant heat tolerance. CtHsfA2b could be used as a candidate gene to genetically modify cool-season grass species or developing molecular markers for improving cool-season grass heat tolerance in the future

Objectives

Methods

Results

Conclusion