A maize heat shock factor ZmHsf11 negatively regulates heat stress tolerance in transgenic plants

A pumpkin heat shock factor CmHSF30 positively regulates thermotolerance in transgenic plants

Heat shock factors (HSFs) play a central role in regulating the responses of plants to various stresses. However, the function and regulation of HSFs in pumpkins remains largely unknown. In this study, an HSF, CmHSF30 was identified in Cucurbiamoschata, which belongs to the HSFA subfamily. The expression level of CmHSF30 was significantly upregulated in response to heat stress and exogenous phytohormone treatments, including ABA, GA, IAA, and SA. The CmHSF30 was localized in the nucleus and functions as a transcriptional activator. By overexpressing CmHSF30 in Arabidopsis and pumpkin, the function and regulation of CmHSF30 in response to heat stress were studied. The overexpression of CmHSF30 in Arabidopsis enhanced plant thermotolerance by increased germination rate and survival rate under heat stress, as evidenced by the elevated of contents chlorophyll and GSH, and SOD activity, and decreased contents of H2O2 and MDA. Furthermore, the overexpression of CmHSF30 in pumpkins also enhanced the thermotolerance of transgenic pumpkins by reducing cell death. In contrast, CRISPR/Cas9 mediated knockout of CmHSF30 decreased pumpkin thermotolerance. Besides, RT-qPCR analysis revealed that CmHSF30 plays a positive role in regulating the expression of stress-related genes, including AtHSP18.2, AtHSP20, AtHSP70, AtPP2C, and AtMYB82 from Arabidopsis and CmHSP18.2, CmHSP20, CmHSP70, CmPP2C, and CmMYB46 from pumpkin. Yeast two-hybrid showed that CmHSF30 interacts with CmMYB46. The results indicate that CmHSF30 functions as a positive regulator, enhancing plant thermotolerance by regulating target genes and reducing ROS accumulation.

The uORF-HsfA1a-WOX11 module controls crown root development in rice

OsWOX11 is a key essential determinant of crown root development in rice. However, either overexpression or downregulation of OsWOX11 results in pleiotropic developmental defects, including dwarfism and reduced yield. Therefore, it is necessary to ensure an optimal level of OsWOX11 expression for balancing the subterranean root system and aerial organ development. OsHsfA1a activates OsWOX11 expression by directly binding to heat stress element-like elements within its promoter. Genetic evidence demonstrated that OsHsfA1a overexpressing or knockout transgenic plants phenocopied the crown root growth in OsWOX11 transgenic plants. Additionally, increased expression of OsWOX11 in OsHsfA1a RNAi background could partially complement the defective crown root phenotypes. A uORF (uORFHsfA1a) was identified within the 5'-untranslated region of OsHsfA1a. Transient expression assays coupled with ribosome profiling revealed that uORFHsfA1a attenuated the translation efficiency of OsHsfA1a mRNA. Furthermore, HsfA1aP:uORFHsfA1a-HsfA1a-GFP plants exhibited wild-type crown root phenotypes, whereas uORFHsfA1a knockout transgenic plants displayed similar crown root phenotypes to OsWOX11 overexpressing plants. These findings suggest that uORFHsfA1a fine-tunes the crown root development by repressing OsHsfA1a translation, thereby indirectly modulating OsWOX11 transcript levels. Our study demonstrated a novel uORFHsfA1a-HsfA1a-WOX11 regulatory module that coordinated transcriptional and translational control to maintain optimal OsWOX11 expression. This mechanism ensures the trade-off between root and shoot development. Importantly, targeting uORFHsfA1a regulatory elements provided a new strategy for engineering robust root system architecture without compromising agronomic traits, thereby addressing a critical challenge in cereal crop improvement.

SmHSFA8 Enhances the Heat Tolerance of Eggplant by Regulating the SmEGY3-SmCSD1 Module and Promoting SmF3H-mediated Flavonoid Biosynthesis

High temperature (HT) is a major environmental factor that restrains eggplant growth and production. Heat shock factors (HSFs) play a vital role in the response of plants to high-temperature stress (HTS). However, the molecular mechanism by which HSFs regulate heat tolerance in eggplants remains unclear. Previously, we reported that SmEGY3 enhanced the heat tolerance of eggplant. Herein, SmHSFA8 activated SmEGY3 expression and interacted with SmEGY3 protein to enhance the activation function of SmEGY3 on SmCSD1. Virus-induced gene silencing (VIGS) and overexpression assays suggested that SmHSFA8 positively regulated heat tolerance in plants. SmHSFA8 enhanced the heat tolerance of tomato plants by promoting SlEGY3 expression, H2O2 production and H2O2-mediated retrograde signalling pathway. DNA affinity purification sequencing (DAP-seq) analysis revealed that SmHSPs (SmHSP70, SmHSP70B and SmHSP21) and SmF3H were candidate downstream target genes of SmHSFA8. SmHSFA8 regulated the expression of HSPs and F3H and flavonoid content in plants. The silencing of SmF3H by VIGS reduced the flavonoid content and heat tolerance of eggplant. In addition, exogenous flavonoid treatment alleviated the HTS damage to eggplants. These results indicated that SmHSFA8 enhanced the heat tolerance of eggplant by activating SmHSPs exprerssion, mediating the SmEGY3-SmCSD1 module, and promoting SmF3H-mediated flavonoid biosynthesis.

Transcription factor PgCDF2 enhances heat tolerance of Physalis grisea by activating heat shock transcription factors PgHSFA1 and PgHSFB3

High temperature influence flower bud differentiation in Physalis grisea, resulting in the production of deformed fruits and affects fruit yield and quality. However, the molecular mechanisms underlying the response of P. grisea to heat stress (HS) remain unclear. In this study, HS treatment and dynamic transcriptome analysis of P. grisea identified the PgCDF2-PgHSFA1/PgHSFB3 transcriptional regulatory module as playing a key role in the response of P. grisea to HS. Gene Ontology (GO) enrichment analysis, transcriptional regulation prediction, and weighted correlation network analysis (WGCNA) of heat stress (HS)-responsive transcriptome data identified three key genes, PgCDF2, PgHSFA1 and PgHSFB3, as components of the regulatory network of heat stress in P. grisea. The expression levels of PgCDF2, PgHSFA1, and PgHSFB3 were up-regulated following exposure to HS. Silencing of PgHSFA1 and PgHSFB3 resulted in reduced heat stress tolerance and altered reactive oxygen species levels in P. grisea. Dual-luciferase assay and Electrophoretic Mobility Shift Assay (EMSA) results indicate that PgCDF2 binds to the promoters of PgHSFA1 and PgHSFB3 and activate their expression. Silencing of PgCDF2 inhibited the expression of PgHSFA1 and PgHSFB3 and also reduced the heat tolerance of P. grisea. In summary, under HS, PgCDF2 enhances the heat tolerance of P. grisea by activating the expression of PgHSFA1 and PgHSFB3. This study clarifies the role of the PgCDF2-PgHSFA1/PgHSFB3 module in the response of P. grisea to HS, providing a theoretical basis for a more in-depth analysis of the molecular mechanisms underlying this response.

Facilitating Maize Seed Germination Under Heat Stress via Exogenous Melatonin

Seed germination is a critical phase during which plants are particularly sensitive to environmental stresses, especially heat stress, due to the high metabolic and physiological activities required for initial growth. Melatonin (MT), a key antioxidant, is crucial for assisting plants in managing abiotic stresses. While the impact of melatonin on heat stress has been explored in other developmental stages or species, this is the first study to specifically focus on its role during maize seed germination under heat stress. The treatment with 50 μM melatonin significantly enhanced seed germination under heat stress by improving antioxidant capacity, osmotic regulation, and hydrolytic enzyme activity, likely through the modulation of key signaling pathways, thus reducing oxidative damage and starch content. Furthermore, melatonin application promoted the accumulation of endogenous gibberellins (GAs) and significantly inhibited abscisic acid (ABA) content, thereby maintaining a dynamic equilibrium between these phytohormones. Principal component analysis and correlation analysis provided deeper insights into the overall effects of these physiological and biochemical parameters. Integrated transcriptomic and metabolomic analysis revealed that melatonin exerted its regulatory effects by modulating key genes and pathways associated with antioxidant defense, stress responses, and plant hormone signal transduction. Furthermore, melatonin significantly modulated the GA and ABA signaling pathways, starch and sucrose metabolism, and phenylpropanoid biosynthesis, thereby reducing oxidative damage induced by heat stress and strengthening the defense mechanisms of maize seeds. The alignment between the qRT-PCR findings and transcriptomic data further validated the robustness of these underlying mechanisms. In conclusion, this study provides novel insights into the role of melatonin in enhancing maize seed germination under heat stress and offers a promising strategy for improving crop heat tolerance through melatonin application in agricultural practices.

Impact of High-Temperature Stress on Maize Seed Setting: Cellular and Molecular Insights of Thermotolerance

Global warming poses a significant threat to crop production and food security, with maize (Zay mays L.) particularly vulnerable to high-temperature stress (HTS). This review explores the detrimental impacts of elevated temperatures on maize development across various growth stages, analyzed within the source-sink framework, with a particular focus on seed setting and yield reduction. It provides a broad analysis of maize cellular and molecular responses to HTS, highlighting the key roles of plant hormone abscisic acid (ABA) signaling, calcium signaling, chloroplast, and the DNA damage repair (DDR) system in maize. HTS disrupts ABA signaling pathways, impairing stomatal regulation and reducing water-use efficiency, while calcium signaling orchestrates stress responses by activating heat shock proteins and other protective mechanisms. Chloroplasts, as central to photosynthesis, are particularly sensitive to HTS, often exhibiting photosystem II damage and chlorophyll degradation. Recent studies also highlight the significance of the DDR system, with genes like ZmRAD51C playing crucial roles in maintaining genomic stability during reproductive organ development. DNA damage under HTS conditions emerges as a key factor contributing to reduced seed set, although the precise molecular mechanisms remain to be fully elucidated. Furthermore, the review examines cutting-edge genetic improvement strategies, aimed at developing thermotolerant maize cultivars. These recent research advances underscore the need for further investigation into the molecular basis of thermotolerance and open the door for future advancements in breeding thermotolerant crops.

RtHSFA9s of Rhodomyrtus tomentosa Positively Regulate Thermotolerance by Transcriptionally Activating RtHSFA2s and RtHSPs

Heat shock transcription factors (HSFs) are crucial components in heat stress response. However, the contribution of the HSFs governing the inherent thermotolerance in Rhodomyrtus tomentosa has barely been investigated. We here compared the roles of RtHSFA9a, RtHSFA9b, and RtHSFA9c in heat stress tolerance. These three genes are the results of gene duplication events, but there exist vast variations in their amino acid sequences. They are all localized to the nucleus. Arabidopsis thaliana plants with overexpressed RtHSFA9a and RtHSFA9c outperformed the wild-type plants, while the over-accumulation of RtHSFA9b had little impact on plant thermotolerance. By transiently overexpressing RtHSFA9a, RtHSFA9b, and RtHSFA9c in R. tomentosa seedlings, the mRNA abundance of heat shock response genes, including RtHSFA2a, RtHSFA2b, RtHSP17.4, RtHSP21.8, RtHSP26.5, and RtHSP70, were upregulated. Transactivation assays confirmed that there exist regulatory divergences among these three genes, viz., RtHSFA9a has the highest transcription activity in regulating RtHSFA2a, RtHSFA2b, RtHSP21.8, and RtHSP70; RtHSFA9c can transcriptionally activate RtHSFA2b, RtHSP21.8, and RtHSP70; RtHSFA9b makes limited contributions to the accumulation of RtHSFA2b, RtHSP21.8, and RtHSP70. Our results indicate that the RtHSFA9 genes make crucial contributions to the thermal adaption of R. tomentosa by positively regulating the RtHSFA2a, RtHSFA2b, and RtHSP genes, which provides novel insights into the RtHSFA9 subfamily.

The heat shock factor 20-HSF4-cellulose synthase A2 module regulates heat stress tolerance in maize

Temperature shapes the geographical distribution and behavior of plants. Understanding the regulatory mechanisms underlying the plant heat stress response is important for developing climate-resilient crops, including maize (Zea mays). To identify transcription factors (TFs) that may contribute to the maize heat stress response, we generated a dataset of short- and long-term transcriptome changes following a heat treatment time course in the inbred line B73. Co-expression network analysis highlighted several TFs, including the class B2a heat shock factor (HSF) ZmHSF20. Zmhsf20 mutant seedlings exhibited enhanced tolerance to heat stress. Furthermore, DNA affinity purification sequencing and Cleavage Under Targets and Tagmentation assays demonstrated that ZmHSF20 binds to the promoters of Cellulose synthase A2 (ZmCesA2) and three class A Hsf genes, including ZmHsf4, repressing their transcription. We showed that ZmCesA2 and ZmHSF4 promote the heat stress response, with ZmHSF4 directly activating ZmCesA2 transcription. In agreement with the transcriptome analysis, ZmHSF20 inhibited cellulose accumulation and repressed the expression of cell wall-related genes. Importantly, the Zmhsf20 Zmhsf4 double mutant exhibited decreased thermotolerance, placing ZmHsf4 downstream of ZmHsf20. We proposed an expanded model of the heat stress response in maize, whereby ZmHSF20 lowers seedling heat tolerance by repressing ZmHsf4 and ZmCesA2, thus balancing seedling growth and defense.

The complex transcriptional regulation of heat stress response in maize

As one of the most important food and feed crops worldwide, maize suffers much more tremendous damages under heat stress compared to other plants, which seriously inhibits plant growth and reduces productivity. To mitigate the heat-induced damages and adapt to high temperature environment, plants have evolved a series of molecular mechanisms to sense, respond and adapt high temperatures and heat stress. In this review, we summarized recent advances in molecular regulations underlying high temperature sensing, heat stress response and memory in maize, especially focusing on several important pathways and signals in high temperature sensing, and the complex transcriptional regulation of ZmHSFs (Heat Shock Factors) in heat stress response. In addition, we highlighted interactions between ZmHSFs and several epigenetic regulation factors in coordinately regulating heat stress response and memory. Finally, we laid out strategies to systematically elucidate the regulatory network of maize heat stress response, and discussed approaches for breeding future heat-tolerance maize.

Characterization of the Heat Shock Transcription Factor Family in Lycoris radiata and Its Potential Roles in Response to Abiotic Stresses

Heat shock transcription factors (HSFs) are an essential plant-specific transcription factor family that regulates the developmental and growth stages of plants, their signal transduction, and their response to different abiotic and biotic stresses. The HSF gene family has been characterized and systematically observed in various species; however, research on its association with Lycoris radiata is limited. This study identified 22 HSF genes (LrHSFs) in the transcriptome-sequencing data of L. radiata and categorized them into three classes including HSFA, HSFB, and HSFC, comprising 10, 8, and 4 genes, respectively. This research comprises basic bioinformatics analyses, such as protein sequence length, molecular weight, and the identification of its conserved motifs. According to the subcellular localization assessment, most LrHSFs were present in the nucleus. Furthermore, the LrHSF gene expression in various tissues, flower developmental stages, two hormones stress, and under four different abiotic stresses were characterized. The data indicated that LrHSF genes, especially LrHSF5, were essentially involved in L. radiata development and its response to different abiotic and hormone stresses. The gene-gene interaction network analysis revealed the presence of synergistic effects between various LrHSF genes' responses against abiotic stresses. In conclusion, these results provided crucial data for further functional analyses of LrHSF genes, which could help successful molecular breeding in L. radiata.

Calcium Signaling and the Response to Heat Shock in Crop Plants

Climate change and the increasing frequency of high temperature (HT) events are significant threats to global crop yields. To address this, a comprehensive understanding of how plants respond to heat shock (HS) is essential. Signaling pathways involving calcium (Ca2+), a versatile second messenger in plants, encode information through temporal and spatial variations in ion concentration. Ca2+ is detected by Ca2+-sensing effectors, including channels and binding proteins, which trigger specific cellular responses. At elevated temperatures, the cytosolic concentration of Ca2+ in plant cells increases rapidly, making Ca2+ signals the earliest response to HS. In this review, we discuss the crucial role of Ca2+ signaling in raising plant thermotolerance, and we explore its multifaceted contributions to various aspects of the plant HS response (HSR).

Exploring the Heat Shock Transcription Factor (HSF) Gene Family in Ginger: A Genome-Wide Investigation on Evolution, Expression Profiling, and Response to Developmental and Abiotic Stresses

Ginger is a valuable crop known for its nutritional, seasoning, and health benefits. However, abiotic stresses, such as high temperature and drought, can adversely affect its growth and development. Heat shock transcription factors (HSFs) have been recognized as crucial elements for enhancing heat and drought resistance in plants. Nevertheless, no previous study has investigated the HSF gene family in ginger. In this research, a total of 25 ZoHSF members were identified in the ginger genome, which were unevenly distributed across ten chromosomes. The ZoHSF members were divided into three groups (HSFA, HSFB, and HSFC) based on their gene structure, protein motifs, and phylogenetic relationships with Arabidopsis. Interestingly, we found more collinear gene pairs between ZoHSF and HSF genes from monocots, such as rice, wheat, and banana, than dicots like Arabidopsis thaliana. Additionally, we identified 12 ZoHSF genes that likely arose from duplication events. Promoter analysis revealed that the hormone response elements (MEJA-responsiveness and abscisic acid responsiveness) were dominant among the various cis-elements related to the abiotic stress response in ZoHSF promoters. Expression pattern analysis confirmed differential expression of ZoHSF members across different tissues, with most showing responsiveness to heat and drought stress. This study lays the foundation for further investigations into the functional role of ZoHSFs in regulating abiotic stress responses in ginger.

Identification of QTN-by-environment interactions for yield related traits in maize under multiple abiotic stresses

INTRODUCTION

Quantitative trait nucleotide (QTN)-by-environment interactions (QEIs) play an increasingly essential role in the genetic dissection of complex traits in crops as global climate change accelerates. The abiotic stresses, such as drought and heat, are the major constraints on maize yields. Multi-environment joint analysis can improve statistical power in QTN and QEI detection, and further help us to understand the genetic basis and provide implications for maize improvement.

METHODS

In this study, 3VmrMLM was applied to identify QTNs and QEIs for three yield-related traits (grain yield, anthesis date, and anthesis-silking interval) of 300 tropical and subtropical maize inbred lines with 332,641 SNPs under well-watered and drought and heat stresses.

RESULTS

Among the total 321 genes around 76 QTNs and 73 QEIs identified in this study, 34 known genes were reported in previous maize studies to be truly associated with these traits, such as ereb53 (GRMZM2G141638) and thx12 (GRMZM2G016649) associated with drought stress tolerance, and hsftf27 (GRMZM2G025685) and myb60 (GRMZM2G312419) associated with heat stress. In addition, among 127 homologs in Arabidopsis out of 287 unreported genes, 46 and 47 were found to be significantly and differentially expressed under drought vs well-watered treatments, and high vs. normal temperature treatments, respectively. Using functional enrichment analysis, 37 of these differentially expressed genes were involved in various biological processes. Tissue-specific expression and haplotype difference analysis further revealed 24 candidate genes with significantly phenotypic differences across gene haplotypes under different environments, of which the candidate genes GRMZM2G064159, GRMZM2G146192, and GRMZM2G114789 around QEIs may have gene-by-environment interactions for maize yield.

DISCUSSION

All these findings may provide new insights for breeding in maize for yield-related traits adapted to abiotic stresses.