Thermotolerant Genes Research Articles

Adaptive capability of slow-growing backyard poultry as indicated by physiological and molecular responses in a hot and humid coastal climate

Assessing the adaptability of slow-growing rural chickens for improving thermotolerance to suit the global climate change is a major research need. This work was aimed to evaluate the adaptability of CARI-Debendra chickens and to identify the polymorphism as well as expression profiling of thermotolerant genes (HSP70 and GRP78) under prevailing temperature-humidity indices and thermal stress in a coastal environment. One hundred sixty straight run chicks were reared at THI≥75 (control) and THI>80 under coastal climate till 12 weeks. Polymorphism of HSP70 and GRP78 candidate genes were explored using restriction enzymes TaqI and HaeIII to identify possible thermotolerance markers. Expression profiling of both the genes in liver, intestine and pectoralis muscle was determined through quantitative real-time PCR. Rectal and body surface temperature recorded in the neck and back showed significant differences (P < 0.01) with higher temperature in THI>80 group. Comparatively lower live weights (P < 0.05) and poor FCR were recorded in THI>80 group. The villi height in all intestinal segments was significantly lower (P < 0.01), but deeper crypt depth was observed in THI>80 than control group. A lowest thymus weight (P < 0.05) was noted with no significant differences in immune response in treatment group. Serum levels of cholesterol, activities of lactate dehydrogenase, creatinine kinase and concentration of potassium, sodium and thyroxine hormone were not different between the 2 groups. The concentration of triiodothyronine and chloride ion was lower in THI>80 group indicating adaptive changes for thermoregulation. HSP70 gene expressions in the three tissues were differentially increased (P < 0.01) by temperature-humidity indices, but the expression of GRP78 was not different between the 2 groups. The results concluded that the environmental factors interact with genetics on adaptability towards thermotolerance in slow-growing chickens.

Identification of anther thermotolerance genes by the integration of linkage and association analysis in maize.

Maize is one of the world's most important staple crops, yet its production is increasingly threatened by the rising frequency of high-temperature stress (HTS). To investigate the genetic basis of anther thermotolerance under field conditions, we performed linkage and association analysis to identify HTS response quantitative trait loci (QTL) using three recombinant inbred line (RIL) populations and an association panel containing 375 diverse maize inbred lines. These analyses resulted in the identification of 16 co-located large QTL intervals. Among the 37 candidate genes identified in these QTL intervals, five have rice or Arabidopsis homologs known to influence pollen and filament development. Notably, one of the candidate genes, ZmDUP707, has been subject to selection pressure during breeding. Its expression is suppressed by HTS, leading to pollen abortion and barren seeds. We also identified several additional candidate genes potentially underly QTL previously reported by other researchers. Taken together, our results provide a pool of valuable candidate genes that could be employed by future breeding programs aiming at enhancing maize HTS tolerance.

Photoperiod and temperature synergistically regulate heading date and regional adaptation in rice.

Plants must accurately integrate external environmental signals with their own development to initiate flowering at the appropriate time for reproductive success. Photoperiod and temperature are key external signals that determine flowering time; both are cyclical and periodic, and they are closely related. In this review, we describe photoperiod-sensitive genes that simultaneously respond to temperature signals in rice (Oryza sativa). We introduce the mechanisms by which photoperiod and temperature synergistically regulate heading date and regional adaptation in rice. We also discuss the prospects for designing different combinations of heading date genes and other cold tolerance or thermo-tolerance genes to help rice better adapt to changes in light and temperature via molecular breeding to enhance yield in the future.

Fine-control of growth and thermotolerance in plant response to heat stress

Global warming impacts plant growth and development, which in turn threatens food security. It has become clear that plants how to response warm-temperature (such as thermomorphogenesis) and high-temperature stress. At the molecular level, many small molecules play crucial roles in balancing growth and defense, achieving high and stable yields by fine-tuning in response to external stimuli. Therefore, it is essential to understand the molecular mechanisms underlying how plants grow in response to heat stress and how they can adjust their biological processes to survive heat stress conditions. In this review, we summarized the heat-responsive genetic networks in plants and crop plants based on recent studies. Focus on how plants sense the elevated temperatures and initiate cellular and metabolic responses that enable them to adapt to the adverse growing conditions. We also describe the trade-off between plant growth and responses to heat stress. Specifically, we address the regulatory network of plant response to the heat stress, which will facilitate the discovery of novel thermotolerant genes and be helpful to open new opportunities for agricultural applications.

Metabolic and Molecular Rearrangements of Sauvignon Blanc (Vitis vinifera L.) Berries in Response to Foliar Applications of Specific Dry Yeast.

Dry yeast extracts (DYE) are applied to vineyards to improve aromatic and secondary metabolic compound content and wine quality; however, systematic information on the underpinning molecular mechanisms is lacking. This work aimed to unravel, through a systematic approach, the metabolic and molecular responses of Sauvignon Blanc berries to DYE treatments. To accomplish this, DYE spraying was performed in a commercial vineyard for two consecutive years. Berries were sampled at several time points after the treatment, and grapes were analyzed for sugars, acidity, free and bound aroma precursors, amino acids, and targeted and untargeted RNA-Seq transcriptional profiles. The results obtained indicated that the DYE treatment did not interfere with the technological ripening parameters of sugars and acidity. Some aroma precursors, including cys-3MH and GSH-3MH, responsible for the typical aromatic nuances of Sauvignon Blanc, were stimulated by the treatment during both vintages. The levels of amino acids and the global RNA-seq transcriptional profiles indicated that DYE spraying upregulated ROS homeostatic and thermotolerance genes, as well as ethylene and jasmonic acid biosynthetic genes, and activated abiotic and biotic stress responses. Overall, the data suggested that the DYE reduced berry oxidative stress through the regulation of specific subsets of metabolic and hormonal pathways.

A review on heat stress altering the insect life history strategies and underlying mechanisms: Special reference to an economically important Lepidoptera, Bombyx mori (Linnaeus, 1758) (Lepidoptera: Bombycidae)

Lepidoptera is an order belonging to class Insecta consisting of Rhopalocera and Heterocera. B. mori belongs to this order and is the backbone of sericulture. Sericulture, the culture, rearing and maintenance of Bombyx mori (Linnaeus, 1785) for silk production, is widely practiced in India, contributing to its economy and providing livelihoods to many, especially those from lower socioeconomic backgrounds. Temperature and humidity affect silk production greatly. Heat shock genes and proteins protect B. mori to a certain extent from increased heat stress. However, outside this range, silkworm biology suffers. The silkworm adapts to heat by upregulating thermotolerance genes and proteins, especially heat shock proteins (HSPs). Produce different heat-resistant proteins at different temperatures. Larvae, embryos, and cocoons are affected by heat stress. Given the silkworm’s sensitivity to temperature and humidity and the alarming pace of climate change and global warming faced by the earth, it is necessary to consider solutions that will allow B. mori to adapt in the future decades. Molecular and enzymatic markers may help screen thermotolerant silkworm breeds. Given this insect’s temperature sensitivity, global warming and climate change may harm it even more than other insects. Therefore, to save this insect and the sericulture sector, steps must be taken in this direction.

Co-expression network analysis of diverse wheat landraces reveals markersof early thermotolerance and a candidate master regulator of thermotolerance genes.

Triticum aestivum L. (bread wheat) is a crop relied upon by billions of people around the world, as a major source of both income and calories. Rising global temperatures, however, pose a genuine threat to the livelihood of these people, as wheat growth and yields are extremely vulnerable to damage by heat stress. Here we present the YoGI wheat landrace panel, comprising 342 accessions that show remarkable phenotypic and genetic diversity thanks to their adaptation to different climates. We quantified the abundance of110 790 transcripts from the panel and used these data to conduct weighted co-expression network analysis and to identify hub genes in modules associated with abiotic stress tolerance. We found that the expression of three hub genes, all heat-shock proteins (HSPs), were significantly correlated with early thermotolerance in a validation panel of landraces. These hub genes belong to the same module, with one (TraesCS4D01G207500.1) being a candidate master-regulator potentially controlling the expression of the other two hub genes, as well as a suite of other HSPs and heat-stress transcription factors (HSFs). In this work, therefore, we identify three validated hub genes, the expression of which can serve as markers of thermotolerance during early development, and suggest that TraesCS4D01G207500.1 is a potential master regulator of HSP and HSF expression - presenting the YoGI landrace panel as an invaluable tool for breeders wishing to determine and introduce novel alleles into modern varieties, for the production of climate-resilient crops.

Thermoregulation in Sheep and Goats: A Review

Thermoregulation is the capability of an animal to maintain its core internal temperature by homeostasis. Small ruminants like sheep and goats acclimate to different environmental changes and often perform better during heat stress than other ruminants. Adapting small ruminants to exceptional weather events occurs through behavioral, genetic, physiological, and morphological mechanisms. Small ruminants can mitigate the consequences of thermal stress using behavioral strategies such as consuming more water, looking for shade, consuming less feed, standing instead of lying down behavior, and other morphological mechanisms such as size, shape, coat color, coat depth, pigmentation, and fat storage. Small ruminants also respond to thermal changes through physiological mechanisms such as variations in respiration, heart rate, core temperature, sweating rate, metabolic rate, and endocrine functions. From the genetic point of view, animals could inherit traits that favor their survival in specific climatic conditions. The adaptation of small ruminants to different thermal environments is determined by an elaborate network of genes with specific genome-wide DNA markers improving toleration to excessive heat. Therefore, genetic identification and analysis of thermotolerance genes should be applied as markers in breeding programs.

Construction of high version thermo-tolerance &amp;lt;italic&amp;gt;Saccharomyces cerevisiae&amp;lt;/italic&amp;gt; by random assembly of thermo-tolerance genetic circuits

<p indent="0mm">Existing green biomanufacturing systems require controlled fermentation at room temperature, consuming large amount of cooling water and energy. To solve this problem, reprogramming the <italic>Saccharomyces cerevisiae</italic> cell factory to improve its thermo-tolerance by randomly assembling the thermo-tolerance gene circuits with the aid of engineering and synthetic biology approaches is developed. In this study, 32 thermo-tolerance genes from <italic>Thermoanaerobacter tengcongensis</italic> MB4, <italic>Thermus thermophiles</italic> HB8, and <italic>Bacillus subtilis</italic> were selected as the core functional elements. The constitutive promoters (14) and terminators (10) with different intensities of <italic>S</italic>. <italic>cerevisiae</italic> were employed as regulatory elements. The thermo-tolerance genes and regulatory elements were randomly assembled by Golden Gate assembly. High-throughput screening of thermo-tolerance yeast was realized based on an automated high-throughput screening platform and high-throughput cell screening. The high version heat-resistant yeast was screened from the secondary screening system of 96-hole deep hole plate-1000 mL triangular flask and the secondary fermentation medium of synthetic medium-real material liquefied mash. Finally, the engineered strains of 4741-GRX5 and 4741-ttha0122 were obtained with residual glucose content of 77.4% and 74.5% of the control (BY4741), respectively. Furthermore, 4741-GRX5 and 4741-ttha0122 were found to augment the ethanol yield by 5.8% and 2.5% compared to BY4741, respectively. Therefore, a new screening platform for heat-resistant strains was established.

Effects of Non-genetic Factors on Production and Reproduction Traits in Tharparkar Cattle under Arid Region of Rajasthan

Background: Tharparkar is one of the important milch breed of cattle for the arid western region of India, which has the capacity to withstand harsh desert climatic conditions and has high thermo-tolerance gene (Bhat et al. 2016) with better reproductive efficiency and milk production. Methods: The present investigation was undertaken on 422 lactation record of 95 cows spread over 30 years from 1990 to 2020, available at ICAR-Central Arid Zone Research Institute, Jodhpur (Rajasthan). Various lactation and reproduction traits in Tharparkar cattle were analysed by using Linear Mixed Model methodology. Result: The overall least-square means were 1803.05±31.59 litre for 305-days lactation yield, 1915.38±36.87 litre for total lactation yield (TLY) in 313.12±4.28 days of lactation length (LL). The peak yield (PY) was 10.29±0.12 litre and days to attain peak yield was 68.12±2.16 days of calving. The least-square means of dry period (DP) and calving interval (CI) were 114.23±4.81 and 427.01±5.49 days, respectively. Significant improvement in production and reproduction traits was observed may be due to selection of high yielding animals and improving management condition of herd. Rigid culling of animals should be followed after 5th lactation onwards to make the dairy farm profitability. Non-significant effect of season of calving indicated the adaptive character against the extreme climatic conditions of the arid zone.

Comparative transcriptomic analysis unveils a network of energy reallocation in Litopenaeus vannamei responsive to heat-stress

Temperature serves as an important environmental factor in ecosystems. Understanding the cooperation of various tissues of animals in response to heat stress is the basis for clarifying the regulation mechanism of different species under heat stress. Herein, a comparative transcriptomic analysis was conducted on three tissues (hepatopancreas, gill and muscle) of the Pacific white shrimp Litopenaeus vannamei under heat stress. Three tissues displayed distinct gene expression patterns, suggesting a cooperation based on division of labor might have occurred among them. In hepatopancreas and gill, genes related to ATP generation and utilization were down-regulated, and energetically expensive protein turnover was almost shut down. While in muscle, genes related to ATP generation and utilization, and those involved in several energy-consuming processes were up-regulated. In consistent, significant accumulation of ATP and decrease of total protein concentration were detected in hepatopancreas and gill, while it was opposite in muscle. Therefore, we suggest that different tissues may cooperate with each other simultaneously via energy reallocation in response to heat stress. Less energy was channeled into protein turnover in gill and hepatopancreas, and more energy was required for muscle. This study not only provides a comprehensive understanding of the molecular mechanism of L. vannamei in response to high temperature, but also lays the foundation of mining thermotolerance genes and proposing effective strategies to cope with the high temperature environment.

Genomic selection signatures in Brazilian sheep breeds reared in a tropical environment

The molecular and genetic effects of heat stress are not as well understood as physiological effects. Heat Stress response should be considered one component of gene network coordinated across various cells, tissues and systems. Its action seeks to minimize the effects of the environment on cellular functions. The detection of selection signatures can identify genes and mutations associated with phenotypic traits even if they are no longer segregating within the populations of interest. This paper looked at 48 sheep breeds (1988 animals), of which 649 animals are from 6 Brazilian breeds reared in a tropical environment. These animals were genotyped using the 50 K SNP Chip. We applied different detection methods (HapFLK and PCAdapt) to identify genomic regions with selection signals (selection signatures). Three groups of breeds were defined, and the first component showed a clear separation between Hair_Warm and Wool_Cold groups. The second component showed some divergence between Wool_Cold and Wool_Warm, with some Hair_Warm breeds located together with Wool_Warm. Hair Brazilian breeds were separated from the others in the first breed component, while the second component segregated European breeds from African and Asian breeds. The four genomic regions identified in chromosomes 2, 7, 11 and 16 harbor several genes related to a wide range of functions. These include production traits (such as milk, growth and reproduction), metabolism (fat and energy), stress response (including immune and inflammation), as well as cell cycle functions. These genomic regions can be a starting point for identifying gene mutations and selecting adapted animals, mainly in a climate change scenario. The locally adapted tropical sheep breeds can be an important genetic reservoir of these thermotolerance genes.

Whole-genome comparative analysis reveals genetic mechanisms of disease resistance and heat tolerance of tropical Bos indicus cattle breeds.

Bos indicus cattle breeds have been naturally selected for thousands of years for disease resistance and thermo-tolerance. However, the genetic mechanisms underlying these specific inherited characteristics must be elucidated. Hence, in this study, a whole-genome comparative analysis of the Bos indicus cattle breeds Kangayam, Tharparkar, Sahiwal, Red Sindhi, and Hariana of the Indian subcontinent was conducted. Genetic variant identification analysis revealed 155 851 012 SNPs and 10 062 805 InDels in the mapped reads across all Bos indicus cattle breeds. The functional annotation of 17 252 genes that comprised both SNPs and InDels, with high functional impact on proteins, was carried out. The functional annotation results revealed the pathways involved in the innate immune response, including toll-like receptors, retinoic acid-inducible gene I-like receptors, NOD-like receptors, Jak-STAT signaling pathways, and non-synonymous variants in the candidate immune genes. We also identified several pathways involved in the heat shock response, hair and skin properties, oxidative stress response, osmotic stress response, thermal sweating, feed intake, metabolism, and non-synonymous variants in the candidate thermo-tolerant genes. These pathways and genes directly or indirectly contribute to the disease resistance and thermo-tolerance adaptations of Bos indicus cattle breeds.

Safeguarding genome integrity under heat stress in plants.

Heat stress adversely affects an array of molecular and cellular events in plant cells, such as denaturation of protein and lipid molecules and malformation of cellular membranes and cytoskeleton networks. Genome organization and DNA integrity are also disturbed under heat stress, and accordingly, plants have evolved sophisticated adaptive mechanisms that either protect their genomes from deleterious heat-induced damages or stimulate genome restoration responses. In particular, it is emerging that DNA damage responses are a critical defense process that underlies the acquirement of thermotolerance in plants, during which molecular players constituting the DNA repair machinery are rapidly activated. In recent years, thermotolerance genes that mediate the maintenance of genome integrity or trigger DNA repair responses have been functionally characterized in various plant species. Furthermore, accumulating evidence supports that genome integrity is safeguarded through multiple layers of thermoinduced protection routes in plant cells, including transcriptome adjustment, orchestration of RNA metabolism, protein homeostasis, and chromatin reorganization. In this review, we summarize topical progresses and research trends in understanding how plants cope with heat stress to secure genome intactness. We focus on molecular regulatory mechanisms by which plant genomes are secured against the DNA-damaging effects of heat stress and DNA damages are effectively repaired. We will also explore the practical interface between heat stress response and securing genome integrity in view of developing biotechnological ways of improving thermotolerance in crop species under global climate changes, a worldwide ecological concern in agriculture.

Differential Modulation of Heat-Inducible Genes Across Diverse Genotypes and Molecular Cloning of a sHSP From Pearl Millet [Pennisetum glaucum (L.) R. Br.

The survival, biomass, and grain yield of most of the crops are negatively influenced by several environmental stresses. The present study was carried out by using transcript expression profiling for functionally clarifying the role of genes belonging to a small heat shock protein (sHSP) family in pearl millet under high-temperature stress. Transcript expression profiling of two high-temperature-responsive marker genes, Pgcp70 and PgHSF, along with physio-biochemical traits was considered to screen out the best contrasting genotypes among the eight different pearl millet inbred lines in the seedling stage. Transcript expression pattern suggested the existence of differential response among different genotypes upon heat stress in the form of accumulation of heat shock-responsive gene transcripts. Genotypes, such as WGI 126, TT-1, TT-6, and MS 841B, responded positively toward high-temperature stress for the transcript accumulation of both Pgcp70 and PgHSF and also indicated a better growth under heat stress. PPMI-69 showed the least responsiveness to transcript induction; moreover, it supports the membrane stability index (MSI) data for scoring thermotolerance, thereby suggesting the efficacy of transcript expression profiling as a molecular-based screening technique for the identification of thermotolerant genes and genotypes at particular crop growth stages. The contrasting genotypes, such as PPMI-69 (thermosusceptible) and WGI-126 and TT-1 (thermotolerant), are further utilized for the characterization of thermotolerance behavior of sHSP by cloning a PgHSP16.97 from the thermotolerant cv. WGI-126. In addition, the investigation was extended for the identification and characterization of 28 different HSP20 genes through a genome-wide search in the pearl millet genome and an understanding of their expression pattern using the RNA-sequencing (RNA-Seq) data set. The outcome of the present study indicated that transcript profiling can be a very useful technique for high-throughput screening of heat-tolerant genotypes in the seedling stage. Also, the identified PgHSP20s genes can provide further insights into the molecular regulation of pearl millet stress tolerance, thereby bridging them together to fight against the unpredicted nature of abiotic stress.

Heat-responsive and time-resolved transcriptome and metabolome analyses of Escherichia coli uncover thermo-tolerant mechanisms

Current understanding of heat shock response has been complicated by the fact that heat stress is inevitably accompanied by changes in specific growth rates and growth stages. In this study, a chemostat culture was successfully performed to avoid the physico-chemical and biological changes that accompany heatshock, which provided a unique opportunity to investigate the full range of cellular responses to thermal stress, ranging from temporary adjustment to phenotypic adaptation at multi-omics levels. Heat-responsive and time-resolved changes in the transcriptome and metabolome of a widely used E. coli strain BL21(DE3) were explored in which the temperature was upshifted from 37 to 42 °C. Omics profiles were categorized into early (2 and 10 min), middle (0.5, 1, and 2 h), and late (4, 8, and 40 h) stages of heat stress, each of which reflected the initiation, adaptation, and phenotypic plasticity steps of the stress response. The continued heat stress modulated global gene expression by controlling the expression levels of sigma factors in different time frames, including unexpected downregulation of the second heatshock sigma factor gene (rpoE) upon the heat stress. Trehalose, cadaverine, and enterobactin showed increased production to deal with the heat-induced oxidative stress. Genes highly expressed at the late stage were experimentally validated to provide thermotolerance. Intriguingly, a cryptic capsular gene cluster showed considerably high expression level only at the late stage, and its expression was essential for cell growth at high temperature. Granule-forming and elongated cells were observed at the late stage, which was morphological plasticity occurred as a result of acclimation to the continued heat stress. Whole process of thermal adaptation along with the genetic and metabolic changes at fine temporal resolution will contribute to far-reaching comprehension of the heat shock response. Further, the identified thermotolerant genes will be useful to rationally engineer thermotolerant microorganisms.

Thermotolerance of tax-2 Is Uncoupled From Life Span Extension and Influenced by Temperature During Development in C. elegans.

Thermotolerance of an organism is a complex trait that is influenced by a multitude of genetic and environmental factors. Many factors controlling thermotolerance in Caenorhabditis elegans are known to extend life. To understand the regulation of thermotolerance, we performed a genetic screen for mutants with better survival at warm temperature. Here we identified by dauer survival a tax-2 mutation and several mutations disrupting an insulin signaling pathway including the daf-2 gene. While the tax-2 mutant has improved thermotolerance and long life span, the newly identified daf-2 and other insulin signaling mutants, unlike the canonical daf-2(e1370), do not show improved thermotolerance despite being long-lived. Examination of tax-2 mutations and their mutant phenotypes suggest that the control of thermotolerance is not coupled with the control of life span or dauer survival. With genetic interaction studies, we concluded that tax-2 has complex roles in life span and dauer survival and that tax-2 is a negative regulator of thermotolerance independent of other known thermotolerance genes including those in the insulin signaling pathway. Moreover, cold growth temperature during development weakens the improved thermotolerance associated with tax-2 and other thermotolerance-inducing mutations. Together, this study reveals previously unknown genetic and environmental factors controlling thermotolerance and their complex relationship with life span regulation.

Identification of Quantitative Trait Loci Controlling High-Temperature Tolerance in Cucumber (Cucumis sativus L.) Seedlings.

High temperature is one of the major abiotic stresses that affect cucumber growth and development. Heat stress often leads to metabolic malfunction, dehydration, wilting and death, which has a great impact on the yield and fruit quality. In this study, genetic analysis and quantitative trait loci (QTL) mapping for thermotolerance in cucumber seedlings was investigated using a recombinant inbred line (RILs; HR) population and a doubled haploid (DH; HP) population derived from two parental lines ‘65G’ (heat-sensitive) and ‘02245′ (heat-tolerant). Inheritance analysis suggested that both short-term extreme and long-term mild thermotolerance in cucumber seedlings were determined by multiple genes. Six QTLs for heat tolerance including qHT3.1, qHT3.2, qHT3.3, qHT4.1, qHT4.2, and qHT6.1 were detected. Among them, the major QTL, qHT3.2, was repeatedly detected for three times in HR and HP at different environments, explained 28.3% of the phenotypic variability. The 481.2 kb region harbored 79 genes, nine of which might involve in heat stress response. This study provides a basis for further identifying thermotolerant genes and helps understanding the molecular mechanism underlying thermotolerance in cucumber seedlings.

An Ancient COI1-Independent Function for Reactive Electrophilic Oxylipins in Thermotolerance.

The jasmonate signaling pathway regulates development, growth, and defense responses in plants. Studies in the model eudicot, Arabidopsis thaliana, have identified the bioactive hormone (jasmonoyl-isoleucine [JA-Ile]) and its Coronatine Insensitive 1 (COI1)/Jasmonate-ZIM Domain (JAZ) co-receptor. In bryophytes, a conserved signaling pathway regulates similar responses but uses a different ligand, the JA-Ile precursor dinor-12-oxo-10,15(Z)-phytodienoic acid (dn-OPDA), to activate a conserved co-receptor. Jasmonate responses independent of JA-Ile and COI1, thought to be mediated by the cyclopentenone OPDA, have also been suggested, but experimental limitations in Arabidopsis have hindered attempts to uncouple OPDA and JA-Ile biosynthesis. Thus, a clear understanding of this pathway remains elusive. Here, we address the role of cyclopentenones in COI1-independent responses using the bryophyte Marchantia polymorpha, which is unable to synthesize JA-Ile but does accumulate OPDA and dn-OPDA. We demonstrate that OPDA and dn-OPDA activate a COI1-independent pathway that regulates plant thermotolerance genes, and consequently, treatment with these oxylipins protects plants against heat stress. Furthermore, we identify that these molecules signal through their electrophilic properties. By performing comparative analyses between M.polymorpha and two evolutionary distant species, A.thaliana and the charophyte alga Klebsormidium nitens, we demonstrate that this pathway is conserved in streptophyte plants and pre-dates the evolutionary appearance of the COI1-dependent jasmonate pathway, which later co-opted the pre-existing dn-OPDA as its ligand. Taken together, our data indicate that cyclopentenone-regulated COI1-independent signaling is an ancient conserved pathway, whose ancestral role was to protect plants against heat stress. This pathway was likely crucial for plants' successful land colonization and will be critical for adaption to current climate warming.

Improvement of Thermotolerance of Zymomonas mobilis by Genes for Reactive Oxygen Species-Scavenging Enzymes and Heat Shock Proteins.

Thermotolerant genes, which are essential for survival at a high temperature, have been identified in three mesophilic microbes, including Zymomonas mobilis. Contrary to expectation, they include only a few genes for reactive oxygen species (ROS)-scavenging enzymes and heat shock proteins, which are assumed to play key roles at a critical high temperature (CHT) as an upper limit of survival. We thus examined the effects of increased expression of these genes on the cell growth of Z. mobilis strains at its CHT. When overexpressed, most of the genes increased the CHT by about one degree, and some of them enhanced tolerance against acetic acid. These findings suggest that ROS-damaged molecules or unfolded proteins that prevent cell growth are accumulated in cells at the CHT.