Regulator Of Thermotolerance Research Articles

Heat shock protein 70 and Cathepsin B genes are involved in the thermal tolerance of Aphis gossypii.

Elevated temperature can directly affect the insect pest population dynamics. Many experimental studies have indicated that high temperatures affect the biological and ecological characteristics of the widely distributed crop pest Aphis gossypii, but the molecular mechanisms underlying its response to heat stress remain unstudied. Here, we used transcriptomic analysis to explore the key genes and metabolic pathways involved in the regulation of thermotolerance in A. gossypii at 29 °C, 32 °C, and 35 °C. The results of bioinformatics analysis show that few genes were consistently differentially expressed among the higher temperature treatments compared to 29 °C, and a moderate temperature increase of 3°C can elicit gene expression changes that help A. gossypii adapt to warmer temperatures. Based on KEGG pathway enrichment analysis, we found that genes encoding four heat shock protein 70 s (Hsp70s) and nine cathepsin B (CathB) proteins were significantly upregulated at 35 °C compared with 32 °C. Genes related to glutathione production were also highly enriched between 32 °C and 29 °C. Silencing of two Hsp70s (ApHsp70A1-1 and ApHsp68) and two CathBs (ApCathB01 and ApCathB02) with RNA interference using a nanocarrier-based transdermal dsRNA delivery system significantly increased sensitivity of A. gossypii to high temperatures. A. gossypii is able to fine-tune its response across a range of temperatures, and Hsp70 and CathB genes are essential for adaption of A. gossypii to warmer temperatures. © 2023 Society of Chemical Industry.

Genetic and Physiological Responses to Heat Stress in Brassica napus.

Given the current rise in global temperatures, heat stress has become a major abiotic challenge affecting the growth and development of various crops and reducing their productivity. Brassica napus, the second largest source of vegetable oil worldwide, experiences a drastic reduction in seed yield and quality in response to heat. This review outlines the latest research that explores the genetic and physiological impact of heat stress on different developmental stages of B. napus with a special attention to the reproductive stages of floral progression, organogenesis, and post flowering. Several studies have shown that extreme temperature fluctuations during these crucial periods have detrimental effects on the plant and often leading to impaired growth and reduced seed production. The underlying mechanisms of heat stress adaptations and associated key regulatory genes are discussed. Furthermore, an overview and the implications of the polyploidy nature of B. napus and the regulatory role of alternative splicing in forming a priming-induced heat-stress memory are presented. New insights into the dynamics of epigenetic modifications during heat stress are discussed. Interestingly, while such studies are scarce in B. napus, opposite trends in expression of key genetic and epigenetic components have been identified in different species and in cultivars within the same species under various abiotic stresses, suggesting a complex role of these genes and their regulation in heat stress tolerance mechanisms. Additionally, omics-based studies are discussed with emphasis on the transcriptome, proteome and metabolome of B. napus, to gain a systems level understanding of how heat stress alters its yield and quality traits. The combination of omics approaches has revealed crucial interactions and regulatory networks taking part in the complex machinery of heat stress tolerance. We identify key knowledge gaps regarding the impact of heat stress on B. napus during its yield determining reproductive stages, where in-depth analysis of this subject is still needed. A deeper knowledge of heat stress response components and mechanisms in tissue specific models would serve as a stepping-stone to gaining insights into the regulation of thermotolerance that takes place in this important crop species and support future breeding of heat tolerant crops.

High-level, constitutive expression of the mgtC gene confers increased thermotolerance on Salmonella enterica serovar Typhimurium.

We found that mutations that increased the transcription of the mgtCBR (Mg2+ transport-related) operon conferred increased thermotolerance on this organism. The 5' leader of the mgtCBR mRNA contains two short open reading frames (ORFs), mgtM and mgtP, whose translation regulates the expression of the mgtCBR operon by a mechanism that is similar to attenuation in amino acid biosynthetic operons. We obtained two types of mutations that resulted in elevated transcription of the operon: defects in the mgtM ribosome-binding site, impairing the translation of this ORF and deletions encompassing the stop codon of mgtM that extend the translation of this ORF across a downstream Rho termination site. These mgtM mutations give further insights into the mechanism of the transcriptional control of the mgtCBR operon that we discuss in this work. We show that the increased thermotolerance requires elevated expression of the mgtC gene, but functional mgtB and mgtR, which respectively encode an Mg2+ transporter and a regulatory protein, are dispensable for this response. MgtC has been shown to have complex functions, including a requirement for virulence, flagella-independent motility and synthesis of cellulose and we now found that it has a role in the regulation of thermotolerance.

Involvement of CsCDPK20 and CsCDPK26 in Regulation of Thermotolerance in Tea Plant (Camellia sinensis)

Calcium-dependent protein kinases (CDPKs) play critical roles in the regulation of plant growth, development, and stress response. In this study, Camellia sinensis CsCDPK1, CsCDPK3, CsCDPK20, and CsCDPK26 were cloned and functionally characterized. Bioinformatics analyses showed that all analyzed CsCDPK genes encoded the expected CDPK structures. Subcellular localization indicated that the four CsCDPK proteins were localized to the cytoplasm and nucleus in onion epidermal cells. The quantitative real-time PCR results indicated that the four CsCDPK genes exhibited tissue-specific expression patterns. Exposure to heat stress and exogenous abscisic acid induced increases in CsCDPK20 and CsCDPK26 transcript abundance at different time points. Furthermore, overexpression of CsCDPK20 and CsCDPK26 increased the thermotolerance in transgenic Arabidopsis thaliana plants. The proline content in leaves was significantly higher in transgenic plants than that in wild-type under heat stress, whereas malondialdehyde content was lower in transgenic plants. Additionally, expression of stress-responsive genes (i.e., AtAPX1, AtPOD, AtProT1, AtP5CS2, AtHSFA2, AtHSP70, AtHSP101, AtRD29B, AtRAB18, AtABI1, AtRBOHD, and AtRBOHF) was increased in the CsCDPK20 and CsCDPK26 transgenic A. thaliana plants compared with that in the wild type. Collectively, our results suggest that CsCDPK20 and CsCDPK26 may act as positive regulator in C. sinensis response to heat stress.

Involvement of Ca2+ and CaM3 in Regulation of Thermotolerance in Lily (Lilium longiflorum)

Involvement of calcium (Ca2+) and different calmodulin (CaM) isoforms in heat shock (HS) signal transduction in lily (Lilium longiflorum) was investigated in this study. Application of CaCl2 enhanced the thermotolerance of lily, whereas treatment with calcium ion chelator EGTA and CaM antagonist trifluoperazine (TFP) lowered the thermotolerance. Besides, HS-induced expression of LlHsf1 and LlHsfA2 genes were up-regulated by CaCl2 and down-regulated by EGTA or TFP. These findings implied that Ca2+–CaM were involved in HS signal transduction in lily via HSF pathway. Subsequently, five LlCaM genes encoding three canonical CaM isoforms were isolated and characterized, among which the LlCaM3 expression was induced by heat and CaCl2 and correlated positively with thermotolerance of lily. Additionally, transient expression analysis determined LlCaM3 to be a cytoplasm and nucleus protein. Furthermore, overexpression of LlCaM3 in Arabidopsis (Arabidopsis thaliana) increased the transcript level of AtHsfA1a and AtHsp18.2 following HS and improved the thermotolerance of transgenic plants. Taken together, the results suggest that LlCaM3 is a key component in Ca2+–CaM HS signaling pathway in lily and may be in the upstream of HSF.

Heat stress-induced BBX18 negatively regulates the thermotolerance in Arabidopsis

There is increasing evidence for considerable interlinking between the responses to heat stress (HS) and light signaling. In the present work, we provide molecular evidence that BBX18, a negative regulator in photomorphogenesis belonging to the B-box zinc finger protein family in Arabidopsis thaliana, is involved in the regulation of thermotolerance. Using quantitative RT-PCR, GUS staining and immunoblot analysis, our results indicate that the expression of BBX18 was induced by HS. BBX18-RNAi and 35S::BBX18 transgenic Arabidopsis plants were obtained for functional analysis of BBX18. Under-expression of BBX18 displayed increased both basal and acquired thermotolerance in the transgenic plants, while over-expression of BBX18 reduced tolerance to HS in transgenic lines. Moreover, when wild-type, BBX18-RNAi and 35S::BBX18 transgenic plants were treated with HS, HR-related digalactosyldiacylglycerol synthase 1 (DGD1) was down-regulated by BBX18 in both normal and heat shock conditions. Besides, the expression levels of Hsp70, Hsp101 and APX2 were increased in BBX18-RNAi transgenic plants, but lower in 35S::BBX18 transgenic plants. However, the expression of HsfA2 was lower in BBX18-RNAi transgenic plants and higher in the 35S::BBX18 after high-temperature treatment. These results suggesting that, by modulated expression of a set of HS-responsive genes, BBX18 weakened tolerance to HS in Arabidopsis. So our data indicate that BBX18 plays a negative role in thermotolerance.

Regulation of Thermotolerance by Stress-Induced Transcription Factors in Saccharomyces cerevisiae

The heat shock transcription factor Hsf1 and the general stress transcription factors Msn2 and Msn4 (Msn2/4) are major regulators of the heat shock response in Saccharomyces cerevisiae. Here, we show that transcriptional activation of their target genes, including HSP104, an antistress chaperone gene, is obligatory for thermotolerance. Although Hsf1 activity might be necessary before the exposure of cells to high temperature, severe heat shock induced the binding of hyperphosphorylated Hsf1 to its target promoters. However, promoter-bound, phosphorylated Hsf1 was inactive for transcription because RNA polymerase II was inactive at high temperatures. Rather, our results suggest that Hsf1 activates the transcription of most of its target genes during the recovery period following severe heat shock. This delayed upregulation by Hsf1, which would be induced by misfolded proteins that accumulate in severely heat-shocked cells, is required for the resumption of normal cell growth. In contrast, the factors Msn2/4 were not involved in the delayed upregulation of genes and were dispensable for cell growth during the recovery period, suggesting that they play a role before the exposure to high temperature. These results show that Hsf1 and Msn2/4 act differentially before and after exposure to extreme temperatures to ensure cell survival and growth.