The Protein Phosphatase RCF2 and Its Interacting Partner

The Protein Phosphatase RCF2and Its Interacting Partner NAC019Are Critical for Heat Stress–Responsive Gene Regulation and Thermotolerance in Arabidopsis W

Qingmei Guan,Xiule Yue,Haitao Zeng,and Jianhua Zhu1

Department of Plant Science and Landscape Architecture,University of Maryland,College Park,Maryland20742

ORCID ID:0000-0003-3258-3071(J.Z.)

Heat stress is a major environmental constraint for crop production worldwide.To respond to and cope with heat stress,plants synthesize heat shock proteins(HSPs),which are often molecular chaperones and are under the control of heat stress transcription factors(HSFs).Very little is known about the upstream regulators of HSFs.In a forward genetic screen for regulators of C-REPEAT BINDING FACTOR(CBF)gene expression(RCFs),we identi?ed RCF2and found that it is allelic to CPL1/FIERY2,which encodes a homolog of C-terminal domain phosphatase.Our results also showed that,in addition to being critical for cold stress tolerance,RCF2is required for heat stress–responsive gene regulation and thermotolerance,because, compared with the wild type,the rcf2-1mutant is hypersensitive to heat stress and because the reduced thermotolerance is correlated with lower expression of most of the21HSFs and some of the HSPs in the mutant plants.We found that RCF2 interacts with the NAC transcription factor NAC019and that RCF2dephosphorylates NAC019in vivo.The nac019mutant is more sensitive to heat stress than the wild type,and chromatin immunoprecipitation followed by quantitative PCR analysis revealed that NAC019binds to the promoters of HSFA1b,HSFA6b,HSFA7a,and HSFC1.Overexpression of RCF2or NAC019in Arabidopsis thaliana increases thermotolerance.Together,our results suggest that,through dephosphorylation of NAC019, RCF2is an integrator of high-temperature signal transduction and a mechanism for HSF and HSP activation.

INTRODUCTION

Land plants are frequently challenged by the changing physical environment that often generates various biotic and abiotic stresses,including heat and drought and sometimes a combina-tion of heat and drought.Heat stress is usually de?ned as a condition in which temperatures are suf?ciently high for enough time to irreversibly damage plant function or development.Heat tolerance is generally de?ned as the ability of the plant to grow and produce economic yield under high temperatures.Heat stress reduces crop production worldwide.The detrimental ef-fects of heat stress can be alleviated by developing heat-tolerant crop plants by various genetic strategies,including traditional and contemporary molecular breeding protocols and transgenic ap-proaches.Although a few plants with improved thermotolerance have been developed through the use of traditional breeding practices,the success of genetic transformation has been limited because of limited knowledge and availability of genes with known effects on plant thermotolerance.Overcoming these limi-tations and developing strategies for improving crop tolerance will require a comprehensive understanding of the physiological responses of plants to high temperature and of the molecular mechanisms of heat tolerance.

Heat stress can adversely impact almost all aspects of plant growth,development,reproduction,and yield.Although every plant tissue is vulnerable to heat stress,the reproductive tissues are particularly susceptible(Zinn et al.,2010).At very high tem-peratures,severe cellular injury and even cell death can occur within a short time(e.g.,within minutes),which may be due to a catastrophic collapse of cellular organization(Schöf?et al.,1999). At moderately high temperatures,injury or cell death may occur only after a relatively long time(e.g.,hours to days).Direct injuries due to high temperature include protein denaturation and ag-gregation and increased?uidity of membrane lipids,while indirect injuries include inactivation of enzymes in chloroplasts and mi-tochondria,inhibition of protein synthesis,protein degradation, loss of membrane integrity,and disruption of cytoskeleton structures(Smertenko et al.,1997;Howarth,2005).These injuries can eventually result in starvation,reduced ion?ux,accumulation of toxic by-products including reactive oxygen species,and disrupted growth and development(Schöf?et al.,1999;Howarth,2005; McClung and Davis,2010;Ruelland and Zachowski,2010;Suzuki et al.,2012).Exposure to heat stress for prolonged periods can even result in plant death,as exempli?ed by the huge loss in maize (Zea mays)and soybean(Glycine max)?elds caused by the de-vastating heat waves in the summer of2012.

To resist heat stress,plants use a variety of mechanisms,in-cluding the maintenance of membrane stability,scavenging of re-active oxygen species,production of antioxidants and compatible organic compounds,induction of mitogen-activated protein kinase and calcium-dependent protein kinase signaling events,and,most importantly,induction of molecular chaperone signaling and tran-scriptional activation(Wahid et al.,2007).A central component of responses to heat stress in all living organisms including plants is

1Address correspondence to jhzhu@umd.edu.

The author responsible for distribution of materials integral to the?ndings

presented in this article in accordance with the policy described in the

Instructions for Authors(http://doc.guandang.net)is:Jianhua Zhu(jhzhu@umd.

edu).

W Online version contains Web-only data.

http://doc.guandang.net/cgi/doi/10.1105/tpc.113.118927

The Plant Cell,Vol.26:438–453,January2014,http://doc.guandang.netã2014American Society of Plant Biologists.All rights reserved.

the induction of heat shock proteins(HSPs)through the action of heat stress transcription factors(HSFs).HSPs are categorized into ?ve classes based on their approximate molecular masses in kD: HSP100,HSP90,HSP70,HSP60,and small HSPs(15to30kD; Vierling,1991;Trent,1996).HSPs function as molec …… 此处隐藏：75499字，全部文档内容请下载后查看。喜欢就下载吧 ……