Heat-inducible SlWRKY3 confers thermotolerance by activating the SlGRXS1 gene cluster in tomato

High temperature stress is one of the major environmental factors that affect the growth and development of plants. Although WRKY transcription factors play a critical role in stress responses, there are few studies on the regulation of heat stress by WRKY transcription factors,especially in tomato. Here, we identified a group I WRKY transcription factor, SlWRKY3, involved in thermotolerance in tomato. First, SlWRKY3 was induced and upregulated under heat stress. Accordingly, overexpression of SlWRKY3 led to an increase, whereas knock-out of SlWRKY3 resulted in decreased tolerance to heat stress. Overexpression of SlWRKY3 accumulated less reactive oxygen species(ROS), whereas knock-out of SlWRKY3 accumulated more ROS under heat stress. This indicated that SlWRKY3 positively regulates heat stress in tomato. In addition,SlWRKY3 activated the expression of a range of abiotic stress-responsive genes involved in ROS scavenging, such as a SlGRXS1 gene cluster.Further analysis showed that SlWRKY3 can bind to the promoters of the SlGRXS1 gene cluster and activate their expression. Collectively, these results imply that SlWRKY3 is a positive regulator of thermotolerance through direct binding to the promoters of the SlGRXS1 gene cluster and activating their expression and ROS scavenging.

Plant VOCs emission： a new strategy of thermotolerance

Plant leaves may emit a substantial amount of volatile organic compounds （VOCs） into the atmosphere, which include isoprene, terpene, alkanes, alkenes, alcohols, aldehydes, eters, esters and carboxylic acids. Furthermore, most of these compounds actively participate in tropospheric chemistry. Great progresses have been made in linking emission of these compounds to climate. However, the VOCs emission function in plant is still not clear. Recently, some evidence has emerged that the production and the emission of VOCs, such as isoprene and monoterpenes, which account for 80% of total VOCs, exhibit plant protection against high temperatures. These increases in VOCs emissions could contribule in a significant way to plant thermotolerance. This perspective summarizes some latest literatures regarding the VOCs emission-dependent thermoprotection in plant species subjected to high temperature stress, presents the achievement in studies concerning plant VOCs emission-dependent thermotolerance, and then exhibits the proposed mechanisms of such plant thermotolerance. Finally open questions regarding the plant VOCs emission were shown, and the future researches were proposed.

GABA Enhances Thermotolerance of Seeds Germination by Attenuating the ROS Damage in Arabidopsis

Seeds germination is strictly controlled by environment factor such as high temperature(HT)through altering the balance between gibberellin acid(GA)and abscisic acid(ABA).Gama-aminobutyric acid(GABA)is a small molecule with four-carbon amino acid,which plays a crucial role during plant physiological process associated with pollination,wounding or abiotic stress,but its role in seeds germination under HT remains elusive.In this study we found that HT induced the overaccumulation of ROS,mainly H_(2)O_(2) and O_(2)^(-),to suppress seeds germination,meanwhile,HT also activated the enzyme activity of GAD for the rapid accumulation of GABA,hinting the regulatory function of GABA in con-trolling seeds germination against HT stress.Applying GABA directly attenuated HT-induced ROS accumulation,upregulated GA biosynthesis and downregulated ABA biosynthesis,ultimately enhanced seeds germination.Consistently,genetic analysis using the gad1/2 mutant defective in GABA biosynthesis,or pop2-5 mutant with high endogenous GABA content supported the potential function of GABA in improving seeds germination tolerance to HT through scavenging ROS overaccumulation.Based on these data,we propose that GABA acts as a novel signal to enhance thermotolerance of seeds germination through alleviating the ROS damage to seeds viability.

<i>α</i>-Mangostin Promotes DAF-16-Mediated Thermotolerance in <i>Caenorhabditis elegans</i>

Garcinia mangostana, commonly known as mangosteen, is a tropical fruit with a reddish-purple pericarp. In Southeast Asia, the pericarp has traditionally been used as a medicine to treat various diseases, including inflammation, wounds, and bacterial infections, as well as aging. α-mangostin is an abundant xanthone in the pericarp, and is thought to play a critical role in the medicinal effects of mangosteens. Previous studies have demonstrated numerous beneficial effects of α-mangostin, such as cytotoxicity in cancer cells. However, the effects of this xanthone in in vivo have not yet been studied. In the current study, C. elegans was used to test the in vivo effects of α-mangostin using several bioassays, including fat accumulation, pharyngeal movement (pumping) and heat-stress assays. Quantitative real time PCR (qRT-PCR) was also used to examine the expression of heat shock proteins. The results revealed that α-mangostin appeared to cause an increase in fat accumulation, which correlated with an increase in pharyngeal movement. The thrashing movement of the worms after heat stress also showed a correlation with an increase in heat shock protein mRNA expression.

Effect of Inorganic Salts on the Thermotolerance and Probiotic Properties of Lactobacilli Isolated from Curdled Milk Traditionally Produced in Mezam Division, Cameroon

The industrial production of most food and probiotic products often requires processing involving high temperatures and physiological stress causing loss of viability of probiotic microbial strains. The viability and stability of probiotic strains is a key determinant of their efficacy during administration in human and animal. Thermotolerance is actually a very important feature for probiotic undergoing industrial processing. This paper aimed at assessing the effect of some mineral salts on the thermotolerance and the probiotic properties of lactobacilli isolated from curded milk produced in Mezam Division, Cameroon. Lactobacilli were isolated by pour plate method on de Man Rogosa and Sharpe (MRS) agar. Lactobacilli were selected based on their ability to suppress in-vitro and in-vivo food borne pathogenic bacteria;Salmonella enterica serovar Enteridis and Esherichia coli. Inhibitory activities against these food borne pathogens were performed by disc diffusion method on Mueller Hinton agar. In-vivo inhibition of Salmonella was achieved using oral administration by gavage of (1.0 × 109 CFU/ml) of selected probiotic strain suspended in sterile water. Thermotolerance was assessed by measuring the survival rate of the strain after heating at various temperatures in the presence and absence of mineral salts. Resistance to bile was determined by measuring the survival rate of probiotics after incubation in the presence of oxgallbille and mineral salts. Two catalase negatives isolates were selected based on their capacity to exhibit inhibitory activities in-vitro and in-vivo against food borne pathogens. They were identified as strain of Lactobacillus casei (LS3) and Lactobacillus plantarum (LM4). These strains exhibited significant reduction (P Salmonella count in caeca swabs of infected chick model. The calcium and magnesium salts increased significantly (P < 0.05) the thermo-tolerance and resistance to bile of probiotic strains studied. These results suggested that calcium and magnesium could be used to monitor the viability of probiotic strains in probiotic products.

Heterologous Expression of Thermolabile Proteins Enhances Thermotolerance in Escherichia coli

Heat shock proteins (HSPs) play important roles in the mechanism of cellular protection against various environmental stresses. It is well known that accumulation of misfolded proteins in a cell triggers the HSPs expression in prokaryotes as well as eukaryotes. In this study, we heterologously expressed two proteins in E. coli, namely, citrate synthase (CpCSY) and malate dehydrogenase (CpMDH) from a psychrophilic bacterium Colwellia psychrerythraea 34H (optimal growth temperature 8°C). Our analyses using circular dichromism along with temperature-dependant enzyme activities measured in purified or direct cell extracts confirmed that the CpCSY and CpMDH are thermolabile and present in misfolded form even at physiological growth temperature. We observed that the cellular levels of HSPs, both GroEL and DnaK cheperonins were increased. Similarly, higher levels were observed for sigma factor s32 which is specific to heat-shock protein expression. These results suggest that the misfolded-thermolabile proteins expressed in E. coli induced the heat shock response. Furthermore, heat treatment (53°C) to wild type E. coli noticeably delayed their growth recovery but cells expressing CpCSY and CpMDH recovered their growth much faster than that of wild type E. coli. This reveals that the HSPs expressed in response to misfolded-thermolabile proteins protected E. coli against heat-induced damage. This novel approach may be a useful tool for investigating stress-tolerance mechanisms of E. coli.

NFXL1 functions as a transcriptional activator required for thermotolerance at reproductive stage in Arabidopsis

Plants are highly susceptible to abiotic stresses,particularly heat stress during the reproductive stage.However,the specific molecular mechanisms underlying this sensitivity remain largely unknown.In the current study,we demonstrate that the Nuclear Transcription Factor,X-box Binding Protein 1-Like 1(NFXL1),directly regulates the expression of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2A(DREB2A),which is crucial for reproductive thermotolerance in Arabidopsis.NFXL1 is upregulated by heat stress,and its mutation leads to a reduction in silique length(seed number)under heat stress conditions.RNA-Seq analysis reveals that NFXL1 has a global impact on the expression of heat stress responsive genes,including DREB2A,Heat Shock Factor A3(HSFA3)and Heat Shock Protein 17.6(HSP17.6)in flower buds.Interestingly,NFXL1 is enriched in the promoter region of DREB2A,but not of either HSFA3 or HSP17.6.Further experiments using electrophoretic mobility shift assay have confirmed that NFXL1 directly binds to the DNA fragment derived from the DREB2A promoter.Moreover,effector-reporter assays have shown that NFXL1 activates the DREB2A promoter.The DREB2A mutants are also heat stress sensitive at the reproductive stage,and DEREB2A is epistatic to NFXL1 in regulating thermotolerance in flower buds.It is known that HSFA3,a direct target of DREB2A,regulates the expression of heat shock proteins genes under heat stress conditions.Thus,our findings establish NFXL1 as a critical upstream regulator of DREB2A in the transcriptional cassette responsible for heat stress responses required for reproductive thermotolerance in Arabidopsis.

A LIMYB305‑LlC3H18‑LIWRKY33 module regulates thermotolerance in lily

The CCCH proteins play important roles in plant growth and development,hormone response,pathogen defense and abiotic stress tolerance.However,the knowledge of their roles in thermotolerance are scarce.Here,we identified a heat-inducible CCCH gene LlC3H18 from lily.LIC3H18 was localized in the cytoplasm and nucleus under normal conditions,while it translocated in the cytoplasmic foci and co-located with the markers of two messenger ribonucleoprotein(mRNP)granules,processing bodies(PBs)and stress granules(SGs)under heat stress conditions,and it also exhibited RNA-binding ability.In addition,LIC3H18 exhibited transactivation activity in both yeast and plant cells.In lily and Arabidopsis,overexpression of LIC3H18 damaged their thermotolerances,and silencing of LIC3H18 in lily also impaired its thermotolerance.Similarly,Arabidopsis atc3h18 mutant also showed decreased thermotolerance.These results indicated that the appropriate expression of C3H18 was crucial for establishing thermotolerance.Further analysis found that LIC3H18 directly bound to the promoter of LIWRKY33 and activated its expression.Besides,it was found that LIMYB305 acted as an upstream factor of LlC3H18 and activated its expression.In conclusion,we demonstrated that there may be a LIMYB305-LlC3H18-LIWRKY33 regulatory module in lily that is involved in the establishment of thermotolerance and finely regulates heat stress response.

Interfering small ubiquitin modifiers(SUMO)improves the thermotolerance of apple by facilitating the activity of MdDREB2A

Heat stress,which is caused by global warming,threatens crops yield and quality across the world.As a kind of post-translation modification,SUMOylation involves in plants heat stress response with a rapid and wide pattern.Here,we identified small ubiquitin modifiers(SUMO),which affect drought tolerance in apple,also participated in thermotolerance.Six isoforms of SUMOs located on six chromosomes in apple genome,and all the SUMOs were up-regulated in response to heat stress condition.The MdSUMO2 RNAi transgenic apple plants exhibited higher survival rate,lower ion leakage,higher catalase(CAT)activity,and Malondialdehyde(MDA)content under heat stress.MdDREB2A,the substrate of MdSUMO2 in apple,was accumulated in MdSUMO2 RNAi transgenic plants than the wild type GL-3 at the protein level in response to heat stress treatment.Further,the inhibited SUMOylation level of MdDREB2A in MdSUMO2 RNAi plants might repress its ubiquitination,too.The accumulated MdDREB2A in MdSUMO2 RNAi plants further induced heat-responsive genes expression to strengthen plants thermotolerance,including MdHSFA3,MdHSP26.5,MdHSP18.2,MdHSP70,MdCYP18-1 and MdTLP1.In summary,these findings illustrate that interfering small ubiquitin modifiers(SUMO)in apple improves plants thermotolerance,partly by facilitating the stability and activity of MdDREB2A.

Exploring the genetic control of sweat gland characteristics in beef cattle for enhanced heat tolerance

Background Thermal stress in subtropical regions is a major limiting factor in beef cattle production systems with around$369 million being lost annually due to reduced performance.Heat stress causes numerous physiological and behavioral disturbances including reduced feed intake and decreased production levels.Cattle utilize various physiological mechanisms such as sweating to regulate internal heat.Variation in these traits can help identify genetic variants that control sweat gland properties and subsequently allow for genetic selection of cattle with greater thermotolerance.Methods This study used 2,401 Brangus cattle from two commercial ranches in Florida.Precise phenotypes that contribute to an animal's ability to manage heat stress were calculated from skin biopsies and included sweat gland area,sweat gland depth,and sweat gland length.All animals were genotyped with the Bovine GGP F250K,and BLUPF90 software was used to estimate genetic parameters and for Genome Wide Association Study.Results Sweat gland phenotypes heritability ranged from 0.17 to 0.42 indicating a moderate amount of the phenotypic variation is due to genetics,allowing producers the ability to select for favorable sweat gland properties.A weighted single-step GWAS using sliding 10 kb windows identified multiple quantitative trait loci(QTLs)explaining a significant amount of genetic variation.QTLs located on BTA7 and BTA12 explained over 1.0%of genetic variance and overlap the ADGRV1 and CCDC168 genes,respectively.The variants identified in this study are implicated in processes related to immune function and cellular proliferation which could be relevant to heat management.Breed of Origin Alleles(BOA)were predicted using local ancestry in admixed populations(LAMP-LD),allowing for identification of markers'origin from either Brahman or Angus ancestry.A BOA GWAS was performed to identify regions inherited from particular ancestral breeds that might have a significant impact on sweat gland phenotypes.Conclusions The results of the BOA GWAS indicate that both Brahman and Angus alleles contribute positively to sweat gland traits,as evidenced by favorable marker effects observed from both genetic backgrounds.Understanding and utilizing genetic traits that confer better heat tolerance is a proactive approach to managing the impacts of climate change on livestock farming.

Arabidopsis Transcription Factors SPL1 and SPL12 Confer Plant Thermotolerance at Reproductive Stage

Plant reproductive organs are vulnerable to heat, but regulation of heat-shock responses in inflorescence is largely uncharacterized. Here, we report that two of the SQUAMOSA PROMOTER BINDING PROTEIN- LIKE （SPL） transcriptional factors in Arabidopsis, SPL1 and SPL12, act redundantly in thermotolerance at the reproductive stage. The spll-1 sp112-1 inflorescences displayed hypersensitivity to heat stress, whereas overexpression of SPL 1 or SPL 12 enhanced the thermotolerance in both Arabidopsis and tobacco. RNA sequencing revealed 1939 upregulated and 1479 downregulated genes in wild-type inflorescence upon heat stress, among which one-quarter （1,040） was misregulated in spll-1 sp112-1, indicating that SPL1 and SPL12 contribute greatly to the heat-triggered transcriptional reprogramming in inflorescence. Notably, heat stress induced a large number of abscisic acid （ABA） responsive genes, of which -39% were disturbed in heat induction in spll-1 sp112-1 inflorescence. Preapplication of ABA and overex- pression of SPL1 restored the inflorescence thermotolerance in spll-1 sp112-1 and in the ABA biosynthesis mutant aba2-1, but not in the pyl sextuple mutant defective in ABA receptors PYR 1/PYL 1/PYL2/PYL4/PYL5/ PYL8. Thus, inflorescence thermotolerance conferred by SPL1 and SPL2 involves PYL-mediated ABA signaling. The molecular network consisting of SPL1 and SPL12 illustrated here shed new light on the mechanisms of plant thermotolerance at the reproductive stage.

Overexpression of Sweet Pepper Glycerol-3-Phosphate Acyltransferase Gene Enhanced Thermotolerance of Photosynthetic Apparatus in Transgenic Tobacco

In order to investigate the relationship between the lipid composition in thylakoid membrane and thermostability of photosynthetic apparatus, tobacco transformed with sweet pepper sense glycerol-3-phosphate acyltransferase （GPAT） gene were used to analyze the lipid composition in thylakoid membrane, the net photosynthetic rate and chlorophyll fluorescence parameters under high temperature stress. The results showed that the saturated extent of monogalactosyldiacylglycerol （MGDG）, sulfoquinovosyldiacylglycerol, digalactosyldiacylglycerol and phosphatidylglycerol in thylakoid membrane of transgenic tobacco T1 lines increased generally. Particularly, the saturated extent in MGDG increased obviously by 16.2% and 12.6% in T1-2 and T1-1, respectively. With stress temperature elevating, the maximum efficiency of photosystem Ⅱ （PSⅡ） photochemistry （Fv/Fm）, actual photochemical efficiency of PSll in the light （ФPSⅡ） and net photosynthetic rate （Pn） of the two lines and wild type tobacco plants decreased gradually, but those parameters decreased much less in transgenic plants. Even though the recovery process appeared differently in the donor and acceptor side of PSⅡ in transgenic tobacco compared with wild-type plants, the entire capability of PSⅡ recovered faster in transgenic tobacco, which was shown in the parameters of PI, Fv/Fm and ФPSⅡ, as a result, the recovery of Pn was accelerated. Conclusively, we proposed that the increase in saturated extent of thylakoid membrane lipids in transgenic plants enhanced the stability of photosynthetic apparatus under high temperature stress.

Thioredoxin Reductase Type C （NTRC） Orchestrates Enhanced Thermotolerance to Arabidopsis by Its Redox-Dependent Holdase Chaperone Function

Genevestigator analysis has indicated heat shock induction of transcripts for NADPH-thioredoxin reduc-tase, type C （NTRC） in the light. Here we show overexpression of NTRC in Arabidopsis （NTRC°E） resulting in enhanced tolerance to heat shock, whereas NTRC knockout mutant plants （ntrcl） exhibit a temperature sensitive phenotype. To investigate the underlying mechanism of this phenotype, we analyzed the protein＇s biochemical properties and protein structure. NTRC assembles into homopolymeric structures of varying complexity with functions as a disulfide reductase, a foldase chaperone, and as a holdase chaperone. The multiple functions of NTRC are closely correlated with protein structure.. Complexes of higher molecular weight （HMW） showed stronger activity as a holdase chaperone, while low molecular weight （LMW） species exhibited weaker holdase chaperone activity but stronger disulfide reductase and fol-dase chaperone activities. Heat shock converted LMW proteins into HMW complexes. Mutations of the two active site Cys residues of NTRC into Ser （C217/454S-NTRC） led to a complete inactivation of its disulfide reductase and foldase chaperone functions, but conferred only a slight decrease in its holdase chaperone function. The overexpression of the mutated C217/454S-NTRC provided Arabidopsis with a similar degree of thermotolerance compared with that of NTRC°E plants. However, after prolonged incubation under heat shock, NTRC°E plants tolerated the stress to a higher degree than C217/454S-NTRC°E plants. The results suggest that the heat shock-mediated holdase chaperone function of NTRC is responsible for the increased thermotolerance of Arabidopsis and the activity is significantly supported by NADPH.

UBA domain protein SUF1 interacts with NatA-complex subunit NAA15 to regulate thermotolerance in Arabidopsis

During recovery from heat stress,plants clear away the heat-stress-induced misfolded proteins through the ubiquitin-proteasome system(UPS).In the UPS,the recognition of substrate proteins by E3 ligase can be regulated by the N-terminal acetyltransferase A(NatA)complex.Here,we determined that Arabidopsis STRESS-RELATED UBIQUITIN-ASSOCIATED-DOMAIN PROTEIN FACTOR 1(SUF1)interacts with the NatA complex core subunit NAA15 and positively regulates NAA15.The suf1 and naa15 mutants are sensitive to heat stress;the NatA substrate NSNC1 is stabilized in suf1 mutant plants during heat stress recovery.Therefore,SUF1 and its interactor NAA15 play important roles in basal thermotolerance in Arabidopsis.

SYP-5 regulates meiotic thermotolerance in Caenorhabditis elegans

Meiosis produces the haploid gametes required by all sexually reproducing organisms,occurring in specific temperature ranges in different organisms.However,how meiotic thermotolerance is regulated remains largely unknown.Using the model organism Caenorhabditis elegans,here,we identified the synaptonemal complex(SC)protein SYP-5 as a critical regulator of meiotic thermotolerance.syp-5-null mutants maintained a high percentage of viable progeny at 20℃ but produced significantly fewer viable progeny at 25℃,a permissive temperature in wild-type worms.Cytological analysis of meiotic events in the mutants revealed that while SC assembly and disassembly,as well as DNA double-strand break repair kinetics,were not affected by the elevated temperature,crossover designation,and bivalent formation were significantly affected.More severe homolog segregation errors were also observed at elevated temperature.A temperature switching assay revealed that late meiotic prophase events were not temperature-sensitive and that meiotic defects during pachytene stage were responsible for the reduced viability of syp-5 mutants at the elevated temperature.Moreover,SC polycomplex formation and hexanediol sensitivity analysis suggested that SYP-5 was required for the normal properties of the SC,and charge-interacting elements in SC components were involved in regulating meiotic thermotolerance.Together,these findings provide a novel molecular mechanism for meiotic thermotolerance regulation.

Brassinosteroids promote thermotolerance through releasing BIN2-mediated phosphorylation and suppression of HsfA1 transcription factors in Arabidopsis

High temperature adversely affects plant growth and development.The steroid phytohormones brassinosteroids(BRs)are recognized to play important roles in plant heat stress responses and thermotolerance,but the underlying mechanisms remain obscure.Here,we demonstrate that the glycogen synthase kinase 3(GSK3)-like kinase BRASSINOSTEROID INSENSITIVE2(BIN2),a negative component in the BR signaling pathway,interacts with the master heat-responsive transcription factors CLASS A1 HEAT SHOCK TRANSCRIPTION FACTORS(HsfA1s).Furthermore,BIN2 phosphorylates HsfA1d on T263 and S56 to suppress its nuclear localization and inhibit its DNA-binding ability,respectively.BR signaling promotes plant thermotolerance by releasing the BIN2 suppression of HsfA1d to facilitate its nuclear localization and DNA binding.Our study provides insights into the molecular mechanisms by which BRs promote plant thermotolerance by strongly regulating HsfA1d through BIN2 and suggests potential ways to improve crop yield under extreme high temperatures.

Fecal Enterococci Levels in Selected Tributaries of the Pampanga River Basin, Philippines, and Their Relation to Land Use

This study aims to generate data which can be used as a potential starting point for the updating of the Philippine Water Quality Criteria and the determination of the true impact of land use to the fecal contamination of the Pampanga River Basin (PRB), the largest subwatershed of Manila Bay. Levels of fecal indicator bacteria (FIB) were determined in the selected tributaries of the PRB, representing three land use categories, namely, the forest/woodland (control), agricultural and residential lands. FIB were quantified in order to investigate the potential contribution of the selected areas in the fecal contamination of the PRB. The study was conducted in 2021 covering March, May, June, July, and September to represent the dry (March and May) and wet (June, July, and September) seasons. Counts of FIB, namely thermotolerant coliform, E. coli, and enterococci were qualitatively correlated with the results of the ocular survey and key informant interview based on known fecal contributors and their relevant rainfall data. FIB counts of water bodies in the selected agricultural and residential land use categories had Geometric Mean (GM) counts that are statistically greater than those of bodies of water near the representative forest/woodland (control), and exceeded the acceptable GM limits for all FIB, regardless of the season. Notably, the GM values recorded for the waters near the selected forest/woodland (control) passed the water quality criteria for all measured FIB parameters for both seasons. Furthermore, enterococci levels in the control site were statistically lower during the wet season. These initial findings suggest that agricultural and residential land use categories could be major contributors to the unacceptable water quality of tributaries of the Pampanga River Basin. The prevalence of thermotolerant coliforms and E. coli was noted regardless of rainfall and land use, indicating these FIB may not be adequate as water quality indicators. With their ability to survive and persist in fecally contaminated sediments in water bodies and in nutrient-poor environments, enterococci could be more definitive indicators of fecal contamination and microbiological quality of environmental waters.

The impact of high-temperature stress on rice: Challenges and solutions

Heat stress (HS) caused by rapidly warming climate has become a serious threat to global food security.Rice (Oryza sativa L.) is a staple food crop for over half of the world’s population,and its yield and quality are often reduced by HS.There is an urgent need for breeding heat-tolerant rice cultivars.Rice plants show various morphological and physiological symptoms under HS.Precise analysis of the symptoms(phenotyping) is essential for the selection of elite germplasm and the identification of thermotolerance genes.In response to HS,rice plants trigger a cascade of events and activate complex transcriptional regulatory networks.Protein homeostasis under HS is especially important for rice thermotolerance,which is affected by protein quality control,effective elimination of toxic proteins,and translational regulation.Although some agronomic and genetic approaches for improving heat tolerance have been adopted in rice,the molecular mechanisms underlying rice response to HS are still elusive,and success in engineering rice thermotolerance in breeding has been limited.In this review,we summarize HS-caused symptoms in rice and progress in heat-stress sensing and signal cascade research,and propose approaches for improving rice thermotolerance in future.

Molecular regulation and genetic control of rice thermal response

Global warming threatens food security.Rice(Oryza sativa L.),a vital food crop,is vulnerable to heat stress,especially at the reproductive stage.Here we summarize putative mechanisms of high-temperature perception(via RNA secondary structure,the phyB gene,and phase separation)and response(membrane fluidity,heat shock factors,heat shock proteins,and ROS(reactive oxygen species)scavenging)in plants.We describe how rice responds to heat stress at different cell-component levels(membrane,endoplasmic reticulum,chloroplasts,and mitochondria)and functional levels(denatured protein elimination,ROS scavenging,stabilization of DNA and RNA,translation,and metabolic flux changes).We list temperature-sensitive genetic male sterility loci available for use in rice hybrid breeding and explain the regulatory mechanisms associated with some of them.Breeding thermotolerant rice species without yield penalties via natural alleles mining and transgenic editing should be the focus of future work.

cDNA Cloning of Heat Shock Protein Genes and Their Expression in an Indigenous Cryptic Species of the Whitefly Bemisia tabaci Complex from China

Thermal adaptation plays a fundamental role in shaping the distribution and abundance of insects,and heat shock proteins（Hsps）play important roles in the temperature adaptation of various organisms.To better understand the temperature tolerance of the indigenous ZHJ2-biotype of whitefly Bemisia tabaci species complex,we obtained complete cDNA sequences for hsp90,hsp70,and hsp20 and analyzed their expression profiles under different high temperature treatments by real-time quantitative polymerase chain reaction.The high temperature tolerance of B.tabaci ZHJ2-biotype was determined by survival rate after exposure to different high temperatures for 1 h.The results showed that after 41°C heat-shock treatment for 1 h,the survival rates of ZHJ2 adults declined significantly and the estimated temperature required to cause 50% mortality（LT50）is 42.85°C for 1 h.Temperatures for onset（Ton）or maximal（Tmax）induction of hsps expression in B.tabaci ZHJ2-biotype were 35 and 39°C（or 41°C）.Compared with previous studies,indigenous ZHJ2-biotype exhibits lower heat temperature stress tolerance and Ton（or Tmax）than the invasive B-biotype.