The transcription factor MYB1 activates DGAT2 transcription to promote triacylglycerol accumulation in sacha inchi (Plukenetia volubilis L.) leaves under heat stress.

Triacylglycerol (TAG) accumulation is frequently triggered in vegetative tissues experiencing heat stress, which may increases plant basal plant thermo-tolerance by sequestering the toxic lipid intermediates that contribute to membrane damage or cell death under stress conditions. However, stress-responsive TAG biosynthesis and the underlying regulatory mechanisms are not fully understood. Here, we investigated the lipidomic and transcriptomic landscape under heat stress in the leaves of sacha inchi (Plukenetia volubilis L.), an important oilseed crop in tropical regions. Under heat stress (45 °C), the content of polyunsaturated TAGs (e.g., TAG18:2 and TAG18:3) and total TAGs were significantly higher, while those of unsaturated sterol esters, including ZyE 28:4, SiE 18:2 and SiE 18:3, were dramatically lower. Transcriptome analysis showed that the expression of PvDGAT2-2, encoding a type II diacylglycerol acyltransferase (DGAT) that is critical for TAG biosynthesis, was substantially induced under heat stress. We confirmed the function of PvDGAT2-2 in TAG production by complementing a yeast mutant defective in TAG biosynthesis. Importantly, we also identified the heat-induced transcription factor PvMYB1 as an upstream activator of PvDGAT2-2 transcription. Our findings on the molecular mechanism leading to TAG biosynthesis in leaves exposed to heat stress have implications for improving the biotechnological production of TAGs in vegetative tissues, offering an alternative to seeds.

Molecular Insights into the Accelerated Sprouting of and Apical Dominance Release in Potato Tubers Subjected to Post-Harvest Heat Stress.

Climate change-induced heat stress (HS) increasingly threatens potato (Solanum tuberosum L.) production by impacting tuberization and causing the premature sprouting of tubers grown during the hot season. However, the effects of post-harvest HS on tuber sprouting have yet to be explored. This study aims to investigate the effects of post-harvest HS on tuber sprouting and to explore the underlying transcriptomic changes in apical bud meristems. The results show that post-harvest HS facilitates potato tuber sprouting and negates apical dominance. A meticulous transcriptomic profiling of apical bud meristems unearthed a spectrum of differentially expressed genes (DEGs) activated in response to HS. During the heightened sprouting activity that occurred at 15-18 days of HS, the pathways associated with starch metabolism, photomorphogenesis, and circadian rhythm were predominantly suppressed, while those governing chromosome organization, steroid biosynthesis, and transcription factors were markedly enhanced. The critical DEGs encompassed the enzymes pivotal for starch metabolism, the genes central to gibberellin and brassinosteroid biosynthesis, and influential developmental transcription factors, such as SHORT VEGETATIVE PHASE, ASYMMETRIC LEAVES 1, SHOOT MERISTEMLESS, and MONOPTEROS. These findings suggest that HS orchestrates tuber sprouting through nuanced alterations in gene expression within the meristematic tissues, specifically influencing chromatin organization, hormonal biosynthesis pathways, and the transcription factors presiding over meristem fate determination. The present study provides novel insights into the intricate molecular mechanisms whereby post-harvest HS influences tuber sprouting. The findings have important implications for developing strategies to mitigate HS-induced tuber sprouting in the context of climate change.

Genome-wide identification and expression analysis reveal the role of histone methyltransferase and demethylase genes in heat stress response in potato (Solanum tuberosum L.).

BACKGROUND: Potato (Solanum tuberosum L.), the third most important non-cereal crop, is sensitive to high temperature. Histone modifications have been known to regulate various abiotic stress responses. However, the role of histone methyltransferases and demethylases remain unexplored in potato under heat stress. METHODS: Potato genome database was used for genome-wide analysis of StPRMT and StHDMA gene families, which were further characterized by analyzing gene structure, conserved motif, domain organization, sub-cellular localization, promoter region and phylogenetic relationships. Additionally, expression profiling under high-temperature stress in leaf and stolon tissue of heat contrasting potato genotypes was done to study their role in response to high temperature stress. RESULTS: The genome-wide analysis led to identification of nine StPRMT and eleven StHDMA genes. Structural analysis, including conserved motifs, exon/intron structure and phylogenetic relationships classified StPRMT and StHDMA gene families into two classes viz. Class I and Class II. A variety of cis-regulatory elements were explored in the promoter region associated with light, developmental, hormonal and stress responses. Prediction of sub-cellular localization of StPRMT proteins revealed their occurrence in nucleus and cytoplasm, whereas StHDMA proteins were observed in different sub-cellular compartments. Furthermore, expression profiling of StPRMT and StHDMA gene family members revealed genes responding to heat stress. Heat-inducible expression of StPRMT1, StPRMT3, StPRMT4 and StPRMT5 in leaf and stolon tissues of HS and HT cultivar indicated them as probable candidates for enhancing thermotolerance in potato. However, StHDMAs responded dynamically in leaf and stolon tissue of heat contrasting genotypes under high temperature. CONCLUSION: The current study presents a detailed analysis of histone modifiers in potato and indicates their role as an important epigenetic regulators modulating heat tolerance. GENERAL SIGNIFICANCE: Understanding epigenetic mechanisms underlying heat tolerance in potato will contribute towards breeding of thermotolerant potato varieties.

StHsfB5 Promotes Heat Resistance by Directly Regulating the Expression of Hsp Genes in Potato.

With global warming, high temperatures have become a major environmental stress that inhibits plant growth and development. Plants evolve several mechanisms to cope with heat stress accordingly. One of the important mechanisms is the Hsf (heat shock factor)-Hsp (heat shock protein) signaling pathway. Therefore, the plant transcription factor Hsf family plays important roles in response to heat stress. All Hsfs can be divided into three classes (A, B, and C). Usually, class-A Hsfs are transcriptional activators, while class-B Hsfs are transcriptional repressors. In potato, our previous work identified 27 Hsfs in the genome and analyzed HsfA3 and HsfA4C functions that promote potato heat resistance. However, the function of HsfB is still elusive. In this study, the unique B5 member StHsfB5 in potato was obtained, and its characterizations and functions were comprehensively analyzed. A quantitative real-time PCR (qRT-PCR) assay showed that StHsfB5 was highly expressed in root, and its expression was induced by heat treatment and different kinds of phytohormones. The subcellular localization of StHsfB5 was in the nucleus, which is consistent with the characterization of transcription factors. The transgenic lines overexpressing StHsfB5 showed higher heat resistance compared with that of the control nontransgenic lines and inhibitory lines. Experiments on the interaction between protein and DNA indicated that the StHsfB5 protein can directly bind to the promoters of target genes small Hsps (sHsp17.6, sHsp21, and sHsp22.7) and Hsp80, and then induce the expressions of these target genes. All these results showed that StHsfB5 may be a coactivator that promotes potato heat resistance ability by directly inducing the expression of its target genes sHsp17.6, sHsp21, sHsp22.7, and Hsp80.

Effect of Glucose Supplementation on Apoptosis in the Pectoralis major of Chickens Raised under Thermoneutral or Heat Stress Environment.

Reduced feed intake during heat stress (HS) disrupts glucose homeostasis, thereby resulting in endoplasmic reticulum (ER) stress and triggering apoptosis in chickens. We hypothesize that glucose supplementation could reduce apoptosis in chickens raised under HS. This study comprised 456 28-day-old broiler chickens randomly assigned to four treatment combinations under glucose supplementation and HS. The treatments were TN0, TN6, HS0, and HS6 with two glucose levels (0% and 6%) and two temperature levels (25 °C (thermoneutral-TN) and 35 °C (8.00 AM to 8.00 PM, (HS)). After 7 days post-HS, the blood glucose level for the HS6 group was higher than for TN0, TN6, and HS0. We studied the mRNA expression of genes and caspase-3 activity in the four experimental groups. The expressions of GCN2, ATF4, CHOP, and FOXO3a increased during HS regardless of glucose supplementation, while PERK and MAFbx increased only under HS with glucose supplementation. We show that under TN conditions, glucose supplementation led to a significant increase in cellular apoptosis in the Pectoralis (P.) major. However, under HS with glucose, the level of apoptosis was similar to that of chickens raised under TN conditions with no glucose supplementation. The utility of glucose to curtail apoptosis under HS should be tested under other intense models of HS.

Molecular analysis of the 14-3-3 genes in Panax ginseng and their responses to heat stress.

Background: Panax Ginseng is a perennial and semi-shady herb with tremendous medicinal value. Due to its unique botanical characteristics, ginseng is vulnerable to various abiotic factors during its growth and development, especially in high temperatures. Proteins encoded by 14-3-3 genes form a highly conserved protein family that widely exists in eukaryotes. The 14-3-3 family regulates the vital movement of cells and plays an essential role in the response of plants to abiotic stresses, including high temperatures. Currently, there is no relevant research on the 14-3-3 genes of ginseng. Methods: The identification of the ginseng 14-3-3 gene family was mainly based on ginseng genomic data and Hidden Markov Models (HMM). We used bioinformatics-related databases and tools to analyze the gene structure, physicochemical properties, cis-acting elements, gene ontology (GO), phylogenetic tree, interacting proteins, and transcription factor regulatory networks. We analyzed the transcriptome data of different ginseng tissues to clarify the expression pattern of the 14-3-3 gene family in ginseng. The expression level and modes of 14-3-3 genes under heat stress were analyzed by quantitative real-time PCR (qRT-PCR) technology to determine the genes in the 14-3-3 gene family responding to high-temperature stress. Results: In this study, 42 14-3-3 genes were identified from the ginseng genome and renamed PgGF14-1 to PgGF14-42. Gene structure and evolutionary relationship research divided PgGF14s into epsilon (ε) and non-epsilon (non-ε) groups, mainly located in four evolutionary branches. The gene structure and motif remained highly consistent within a subgroup. The physicochemical properties and structure of the predicted PgGF14 proteins conformed to the essential characteristics of 14-3-3 proteins. RNA-seq results indicated that the detected PgGF14s existed in different organs and tissues but differed in abundance; their expression was higher in roots, stems, leaves, and fruits but lower in seeds. The analysis of GO, cis-acting elements, interacting proteins, and regulatory networks of transcription factors indicated that PgGF14s might participate in physiological processes, such as response to stress, signal transduction, material synthesis-metabolism, and cell development. The qRT-PCR results indicated PgGF14s had multiple expression patterns under high-temperature stress with different change trends in several treatment times, and 38 of them had an apparent response to high-temperature stress. Furthermore, PgGF14-5 was significantly upregulated, and PgGF14-4 was significantly downregulated in all treatment times. This research lays a foundation for further study on the function of 14-3-3 genes and provides theoretical guidance for investigating abiotic stresses in ginseng.

Physiological and transcriptional responses to heat stress in a typical phenotype of Pinellia ternata.

Pinellia ternata is an important medicinal plant, and its growth and development are easily threatened by high temperature. In this study, comprehensive research on physiological, cytological and transcriptional responses to different levels of heat stress were conducted on a typical phenotype of P. ternata. First, P. ternata exhibited tolerance to the increased temperature, which was supported by normal growing leaves, as well as decreased and sustained photosynthetic parameters. Severe stress aggravated the damages, and P. ternata displayed an obvious leaf senescence phenotype, with significantly increased SOD and POD activities (46% and 213%). In addition, mesophyll cells were seriously damaged, chloroplast thylakoid was fuzzy, grana lamellae and stroma lamellae were obviously broken, and grana thylakoids were stacked, resulting in a dramatically declined photosynthetic rate (74.6%). Moreover, a total of 16 808 genes were significantly differential expressed during this process, most of which were involved in photosynthesis, transmembrane transporter activity and plastid metabolism. The number of differentially expressed transcription factors in MYB and bHLH families was the largest, indicating that these genes might participate in heat stress response in P. ternata. These findings provide insight into the response to high temperature and facilitate the standardized cultivation of P. ternata.

Thermosensitivity of pollen: a molecular perspective.

A current trend in climate comprises adverse weather anomalies with more frequent and intense temperature events. Heatwaves are a serious threat to global food security because of the susceptibility of crop plants to high temperatures. Among various developmental stages of plants, even a slight rise in temperature during reproductive development proves detrimental, thus making sexual reproduction heat vulnerable. In this context, male gametophyte or pollen development stages are the most sensitive ones. High-temperature exposure induces pollen abortion, reducing pollen viability and germination rate with a concomitant effect on seed yield. This review summarizes the ultrastructural, morphological, biochemical, and molecular changes underpinning high temperature-induced aberrations in male gametophytes. Specifically, we highlight the temperature sensing cascade operating in pollen, involving reactive oxygen species (ROS), heat shock factors (HSFs), a hormones and transcriptional regulatory network. We also emphasize integrating various omics approaches to decipher the molecular events triggered by heat stress in pollen. The knowledge of genes, proteins, and metabolites conferring thermotolerance in reproductive tissues can be utilized to breed/engineer thermotolerant crops to ensure food security.

miRNAs and Their Target Genes Play a Critical Role in Response to Heat Stress in Cynodon dactylon (L.) Pers.

Annual global temperature is increasing rapidly. Therefore, in the near future, plants will be exposed to severe heat stress. However, the potential of microRNAs-mediated molecular mechanism for modulating the expression of their target genes is unclear. To investigate the changes of miRNAs in thermo-tolerant plants, in this study, we first investigated the impact of four high temperature regimes including 35/30 °C, 40/35 °C, 45/40 °C, and 50/45 °C in a day/night cycle for 21 days on the physiological traits (total chlorophyll, relative water content and electrolyte leakage and total soluble protein), antioxidant enzymes activities (superoxide dismutase, ascorbic peroxidase, catalase and peroxidase), and osmolytes (total soluble carbohydrates and starch) in two bermudagrass accessions named Malayer and Gorgan. The results showed that more chlorophyll and the relative water content, lower ion leakage, more efficient protein and carbon metabolism and activation of defense proteins (such as antioxidant enzymes) in Gorgan accession, led to better maintained plant growth and activity during heat stress. In the next stage, to investigate the role of miRNAs and their target genes in response to heat stress in a thermo-tolerant plant, the impact of severe heat stress (45/40 °C) was evaluated on the expression of three miRNAs (miRNA159a, miRNA160a and miRNA164f) and their target genes (GAMYB, ARF17 and NAC1, respectively). All measurements were performed in leaves and roots simultaneously. Heat stress significantly induced the expression of three miRNAs in leaves of two accession, while having different effects on the expression of these miRNAs in roots. The results showed that a decrease in the expression of the transcription factor ARF17, no change in the expression of the transcription factor NAC1, and an increase in the expression of the transcription factor GAMYB in leaf and root tissues of Gorgan accession led to improved heat tolerance in it. These results also showed that the effect of miRNAs on the modulating expression of target mRNAs in leaves and roots is different under heat stress, and miRNAs and mRNAs show spatiotemporal expression. Therefore, the simultaneous analysis of miRNAs and mRNAs expressions in shoot and roots is needed to comprehensively understand miRNAs regulatory function under heat stress.

Effects of dietary supplementation of cumin (Cuminum cyminum L.) essential oil on expression of genes related to antioxidant, apoptosis, detoxification, and heat shock mechanism in heat-stressed broiler chickens.

This study was carried out to evaluate the impact of cumin essential oil (CEO) supplementation on levels of certain gene expression related to antioxidant, apoptotic, detoxific, and heat shock mechanisms in the breast meat and ileum of heat-stressed broilers. The study was conducted on a 2 × 6 factorial design (heat stress + feed additive) on 600 day-old male broiler chicks for a period of 42 days. From day 7 to 42, although broilers in heat stress groups (HT) were exposed to constant chronic heat stress (36 °C), others were housed at thermoneutral ambient temperature (TN). The chicks in both conditions were fed with 6 experimental diets: C0 (basal diet with no additive), ANTIB (basal diet + 100 mg/kg chloramphenicol), VITE (basal diet + 50 IU α-tocopherol), C2 (basal diet + 200 mg/kg CEO), C4 (basal diet + 400 mg/kg CEO), C6 (basal diet+ 600 mg/kg CEO). The results showed that heat stress upregulated (except for Bcl-2) the genes related to antioxidant, apoptosis, detoxification, and heat shock mechanism. However, cumin essential oil increased the dose-dependently positive effect on certain genes in tissues of the heat-stressed broilers and downregulated (except for Bcl-2) these genes.

Effect of selenium nanoparticles on alternative splicing in heat-stressed rainbow trout primary hepatocytes.

Alternative splicing (AS) is a ubiquitous post-transcriptional regulatory mechanism in eukaryotes that generates multiple mRNA isoforms from a single gene, increasing diversity of mRNAs and proteins that are essential for eukaryotic developmental processes and responses to environmental stress. Results showed that a total of 37,463 AS events were identified in rainbow trout hepatocytes. In addition, a total of 364 differential alternative splicing (DAS) events were identified in hepatocytes under selenium nanoparticles (SeNPs) and 3632 DAS events were identified under a combination of SeNPs and heat stress (24 °C). Gene Ontology (GO) enrichment showed that some subcategories "immune effector processes", "response to stimuli" and "antioxidant activity" were associated with immunity, abiotic stimuli and antioxidants. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment showed that differentially expressed genes (DEGs) were significantly enriched in spliceosomes by adding SeNPs in heat-stressed hepatocytes. Splicing factor family (SRSF3, SRSF7, SRSF9, U2AF1 and U2AF2) and pre-RNA splicing factors (ACIN1 and PPRF18) were significantly upregulated and promoted AS. Furthermore, addition of SeNPs activated the phosphatidylinositol signaling system and upregulated the related genes PI4KA, DGKH, ITPK1 and Ocrl, and thus attenuated the inflammatory response to heat stress and enhanced resistance to heat stress by activating the adherent plaque kinase-PI3K-Akt signaling pathway and calcium channels. Those findings suggested that AS could be an essential regulatory mechanism in adaptation of rainbow trout to heat-stressed environments.

Physiological and transcriptional responses to heat stress in a typical phenotype of Pinellia ternata / 中国天然药物

Pinellia ternata is an important medicinal plant, and its growth and development are easily threatened by high temperature. In this study, comprehensive research on physiological, cytological and transcriptional responses to different levels of heat stress were conducted on a typical phenotype of P. ternata. First, P. ternata exhibited tolerance to the increased temperature, which was supported by normal growing leaves, as well as decreased and sustained photosynthetic parameters. Severe stress aggravated the damages, and P. ternata displayed an obvious leaf senescence phenotype, with significantly increased SOD and POD activities (46% and 213%). In addition, mesophyll cells were seriously damaged, chloroplast thylakoid was fuzzy, grana lamellae and stroma lamellae were obviously broken, and grana thylakoids were stacked, resulting in a dramatically declined photosynthetic rate (74.6%). Moreover, a total of 16 808 genes were significantly differential expressed during this process, most of which were involved in photosynthesis, transmembrane transporter activity and plastid metabolism. The number of differentially expressed transcription factors in MYB and bHLH families was the largest, indicating that these genes might participate in heat stress response in P. ternata. These findings provide insight into the response to high temperature and facilitate the standardized cultivation of P. ternata.

Transcriptomic Analysis of the Porcine Gut in Response to Heat Stress and Dietary Soluble Fiber from Beet Pulp.

This study aimed to investigate the impact of heat stress (HS) and the effects of dietary soluble fiber from beet pulp (BP) on gene expression (differentially expressed genes, DEGs) of the porcine jejunum. Out of the 82 DEGs, 47 genes were up-regulated, and 35 genes were downregulated between treatments. The gene ontology (GO) enrichment analysis showed that the DEGs were related mainly to the actin cytoskeleton organization and muscle structure development in biological processes, cytoplasm, stress fibers, Z disc, cytoskeleton, and the extracellular regions in cellular composition, and actin binding, calcium ion binding, actin filament binding, and pyridoxal phosphate binding in the molecular function. The KEGG pathway analysis showed that the DEGs were involved in hypertrophic cardiomyopathy, dilated cardiomyopathy, vascular smooth muscle contraction, regulation of actin cytoskeleton, mucin type O-glycan biosynthesis, and African trypanosomiasis. Several of the genes (HSPB6, HSP70, TPM1, TAGLN, CCL4) in the HS group were involved in cellular oxidative stress, immune responses, and cellular differentiation. In contrast, the DEGs in the dietary BP group were related to intestinal epithelium integrity and immune response to pathogens, including S100A2, GCNT3, LYZ, SCGB1A1, SAA3, and ST3GAL1. These findings might help understand the HS response and the effect of dietary fiber (DF) regarding HS and be a valuable reference for future studies.

Heat shock-induced failure of meiosis I to meiosis II transition leads to 2n pollen formation in a woody plant.

The formation of diploid gametes through chromosome doubling is a major mechanism of polyploidization, diversification, and speciation in plants. Unfavorable climate conditions can induce or stimulate the production of diploid gametes during meiosis. Here, we demonstrated that heat shock stress (38°C for 3 or 6 h) induced 2n pollen formation, and we generated 42 triploids derived from heat shock-induced 2n pollen of Populus canescens. Meiotic analysis of treated pollen mother cells revealed that induced 2n pollen originated from the complete loss of meiosis II (MII). Among the 42 triploids, 38 triploids derived from second division restitution (SDR)-type 2n pollen and 4 triploids derived from first division restitution-type 2n pollen were verified using simple sequence repeats (SSR) molecular markers. Twenty-two differentially expressed genes related to the cell cycle were identified and characterized by expression profile analysis. Among them was POPTR_0002s08020g (PtCYCA1;2), which encodes a type A Cyclin CYCA1;2 that is required for the meiosis I (MI) to MII transition. After male flower buds were exposed to heat shock, a significant reduction was detected in PtCYCA1;2 expression. We inferred that the failure of MI-to-MII transitions might be associated with downregulated expression of PtCYCA1;2, leading to the formation of SDR-type 2n pollen. Our findings provide insights into mechanisms of heat shock-induced 2n pollen formation in a woody plant and verify that sensitivity to environmental stress has evolutionary importance in terms of polyploidization.

[Drought and Heat Stress-Mediated Modulation of Alternative Splicing in the Genes Involved in Biosynthesis of Metabolites Related to Tea Quality].

Alternative splicing (AS) regulates mRNAs at the post-transcriptional level to affect both their amounts and the protein function. However, little is known about the roles of AS in regulation of biosynthesis of amino acids, flavonoids, and volatile compounds in tea plants. In this study, we used Iso-seq and transcriptome deep sequencing (RNA-seq) to identify AS events, and analyzed the expression of respective mRNAs in tea plants under drought (DS), heat stress (HS), and their combination (HD). By RT-PCR, we validated the AS events in nine genes involved in the biosynthesis of amino acids and flavonoids. The genes accumulating AS transcripts under DS, HS, and HD conditions included those encoding for anthocyanidin reductase (ANR), dihydrofavonol-4-reductase-like (DFRA), and chalcone isomerase (CHI). Similarly, genes directly or indirectly involved in the biosynthesis of volatile compounds such as lipoxygenase (LOX), terpenoid/terpene synthase (TPS), and 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) also had AS events. Our study revealed that AS might specifically regulate the biosynthesis of amino acids in tea plants under stressful conditions. Moreover, we suggest that the AS events within the ANR and DFRA transcripts might play an important role in the regulation of flavonoid biosynthesis under DS, HS, and HD conditions. This study improved our understanding of the genetic drivers of the changes in the content of bioactive ingredients of tea plants subjected to abiotic stresses.

Genome-wide identification of PEBP gene family members in potato, their phylogenetic relationships, and expression patterns under heat stress.

BACKGROUND: The phosphatidylethanolamine-binding protein (PEBP) gene family is involved in regulating many plant traits. Genome-wide identification of PEPB members and knowledge of their responses to heat stress may assist genetic improvement of potato (Solanum tuberosum). METHODS AND RESULTS: We identified PEBP gene family members from both the recently-updated, long-reads-based reference genome (DM v6.1) and the previous short-reads-based annotation (PGSC DM v3.4) of the potato reference genome and characterized their heat-induced gene expression using RT-PCR and RNA-Seq. Fifteen PEBP family genes were identified from DM v6.1 and named as StPEBP1 to StPEBP15 based on their locations on 6 chromosomes and were classified into FT, TFL, MFT, and PEBP-like subfamilies. Most of the StPEBP genes were found to have conserved motifs 1 to 5. Tandem or segmental duplications were found between StPEBP genes in seven pairs. Heat stress induced opposite expression patterns of certain FT and TFL members but involving different members in leaves, roots and tubers. CONCLUSION: The long-reads-based genome assembly and annotation provides a better genomic resource for identification of PEBP family genes. Heat stress tends to decrease FT gene activities but increases TFL gene activities, but this opposite expression involves different FT/TFL pairs in leaves, roots, and tubers. This tissue-specific expression pattern of PEBP members may partly explain why different potato organs differ in their sensitivities to heat stress. Our study provides candidate PEBP family genes and relevant information for genetic improvement of heat tolerance in potato and may help understand heat-induced responses in other plants.

Pollen viability as a potential trait for screening heat-tolerant wheat (Triticum aestivum L.).

High temperature during reproductive stage of winter crops causes sterility of pollen grains and reduced yield. It is essential to find the genotypes with higher pollen viability, as it is most sensitive to temperature extremes. A field study was conducted with wheat (Triticum aestivum L.) genotypes to understand the effect of high temperature on pollen viability and grain yield for 2years under timely (TS) and late sown (LS) conditions. A strong correlation was observed between higher pollen viability and higher grain yield under heat stress condition. Genotypes like K7903, HD2932, WH730 and RAJ3765 showed higher pollen viability, whereas DBW17, HUW468, RAJ4014 and UP2425 had lower pollen viability under LS condition. Further, the quantification of antioxidant enzymes activity mainly, Super oxide dismutase (SOD), Catalase (CAT), Peroxidase (POD) and Glutathione peroxidase (GPX) has showed significant variation among study genotypes. Thus, the identified high pollen viability genotypes can serve as a potential source for trait based breeding under heat stress in wheat. The present study is a first of its kind to assess more number of wheat genotypes for pollen viability and antioxidants activity under field condition. It also confirms that pollen viability can be used as a potential trait to screen genotypes for heat stress tolerance in wheat.

In vitro effects of 5-Hydroxy-L-tryptophan supplementation on primary bovine mammary epithelial cell gene expression under thermoneutral or heat shock conditions.

Serotonin (5-HT) is an autocrine-paracrine molecule within the mammary gland regulating homeostasis during lactation and triggering involution after milk stasis. Exposure of dairy cows to hyperthermia during the dry period alters mammary gland involution processes leading to reduced subsequent yields. Herein, primary bovine mammary epithelial cells (pBMEC) under thermoneutral (TN, 37 °C) or heat shock (HS, 41.5 °C) conditions were cultured with either 0, 50, 200, or 500 µM 5-Hydroxy-L-tryptophan (5-HTP; 5-HT precursor) for 8-, 12- or 24-h. Expression of 95 genes involved in 5-HT signaling, involution and tight junction regulation were evaluated using a Multiplex RT-qPCR BioMark Dynamic Array Circuit. Different sets of genes were impacted by 5-HTP or temperature, or by their interaction. All 5-HT signaling genes were downregulated after 8-h of HS and then upregulated after 12-h, relative to TN. After 24-h, apoptosis related gene, FASLG, was upregulated by all doses except TN-200 µM 5-HTP, and cell survival gene, FOXO3, was upregulated by HS-50, 200 and 500 µM 5-HTP, suggesting 5-HTP involvement in cell turnover under HS. Supplementing 5-HTP at various concentrations in vitro to pBMEC modulates the expression of genes that might aid in promoting epithelial cell turn-over during involution in dairy cattle under hyperthermia.

Holistic insights from pollen omics: co-opting stress-responsive genes and ER-mediated proteostasis for male fertility.

Sexual reproduction in flowering plants takes place without an aqueous environment. Sperm are carried by pollen through air to reach the female gametophyte, though the molecular basis underlying the protective strategy of the male gametophyte is poorly understood. Here we compared the published transcriptomes of Arabidopsis thaliana pollen, and of heat-responsive genes, and uncovered insights into how mature pollen (MP) tolerates desiccation, while developing and germinating pollen are vulnerable to heat stress. Germinating pollen expresses molecular chaperones or "heat shock proteins" in the absence of heat stress. Furthermore, pollen tubes that grew through pistils at basal temperature showed induction of the endoplasmic reticulum (ER) stress response, which is a characteristic of stressed vegetative tissues. Recent studies show MP contains mRNA-protein (mRNP) aggregates that resemble "stress" granules triggered by heat or other stresses to protect cells. Based on these observations, we postulate that mRNP particles are formed in maturing pollen in response to developmentally programmed dehydration. Dry pollen can withstand harsh conditions as it is dispersed in air. We propose that, when pollen lands on a compatible pistil and hydrates, mRNAs stored in particles are released, aided by molecular chaperones, to become translationally active. Pollen responds to osmotic, mechanical, oxidative, and peptide cues that promote ER-mediated proteostasis and membrane trafficking for tube growth and sperm discharge. Unlike vegetative tissues, pollen depends on stress-protection strategies for its normal development and function. Thus, heat stress during reproduction likely triggers changes that interfere with the normal pollen responses, thereby compromising male fertility. This holistic perspective provides a framework to understand the basis of heat-tolerant strains in the reproduction of crops.

A standardized extract of Asparagus officinalis stem improves HSP70-mediated redox balance and cell functions in bovine cumulus-granulosa cells.

Heat shock (HS) protein 70 (HSP70), a well-known HS-induced protein, acts as an intracellular chaperone to protect cells against stress conditions. Although HS induces HSP70 expression to confer stress resistance to cells, HS causes cell toxicity by increasing reactive oxygen species (ROS) levels. Recently, a standardized extract of Asparagus officinalis stem (EAS), produced from the byproduct of asparagus, has been shown to induce HSP70 expression without HS and regulate cellular redox balance in pheochromocytoma cells. However, the effects of EAS on reproductive cell function remain unknown. Here, we investigated the effect of EAS on HSP70 induction and oxidative redox balance in cultured bovine cumulus-granulosa (CG) cells. EAS significantly increased HSP70 expression; however, no effect was observed on HSP27 and HSP90 under non-HS conditions. EAS decreased ROS generation and DNA damage and increased glutathione (GSH) synthesis under both non-HS and HS conditions. Moreover, EAS synergistically increased HSP70 and HSF1 expression and increased progesterone levels in CG cells. Treatment with an HSP70 inhibitor significantly decreased GSH level, increased ROS level, and decreased HSF1, Nrf2, and Keap1 expression in the presence of EAS. Furthermore, EAS significantly increased progesterone synthesis. Thus, EAS improves HSP70-mediated redox balance and cell function in bovine CG cells.