Clock-regulated coactivators selectively control gene expression in response to different temperature stress conditions in Arabidopsis.

Plants respond to severe temperature changes by inducing the expression of numerous genes whose products enhance stress tolerance and responses. Dehydration-responsive element (DRE)-binding protein 1/C-repeat binding factor (DREB1/CBF) transcription factors act as master switches in cold-inducible gene expression. Since DREB1 genes are rapidly and strongly induced by cold stress, the elucidation of the molecular mechanisms of DREB1 expression is vital for the recognition of the initial responses to cold stress in plants. A previous study indicated that the circadian clock-related MYB-like transcription factors REVEILLE4/LHY-CCA1-Like1 (RVE4/LCL1) and RVE8/LCL5 directly activate DREB1 expression under cold stress conditions. These RVEs function in the regulation of circadian clock-related gene expression under normal temperature conditions. They also activate the expression of HSF-independent heat-inducible genes under high-temperature conditions. Thus, there are thought to be specific regulatory mechanisms whereby the target genes of these transcription factors are switched when temperature changes are sensed. We revealed that NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED (LNK) proteins act as coactivators of RVEs in cold and heat stress responses in addition to regulating circadian-regulated genes at normal temperatures. We found that among the four Arabidopsis LNKs, LNK1 and LNK2 function under normal and high-temperature conditions, and LNK3 and LNK4 function under cold conditions. Thus, these LNK proteins play important roles in inducing specific genes under different temperature conditions. Furthermore, LNK3 and LNK4 are specifically phosphorylated under cold conditions, suggesting that phosphorylation is involved in their activation.

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.

HSP70A promotes the photosynthetic activity of marine diatom Phaeodactylum tricornutum under high temperature.

With global climate change, the high-temperature environment has severely impacted the community structure and phenotype of marine diatoms. Phaeodactylum tricornutum, a model species of marine diatom, is sensitive to high temperature, which grow slowly under high temperature. However, the regulatory mechanism of P. tricornutum in response to high-temperature is still unclear. In this study, we found that the expression level of the HSP70A in the wild type (WT) increased 28 times when exposed to high temperature (26°C) for 1 h, indicating that HSP70A plays a role in high temperature in P. tricornutum. Furthermore, overexpression and interference of HSP70A have great impact on the exponential growth phase of P. tricornutum under 26°C. Moreover, the results of Co-immunoprecipitation (Co-IP) suggested that HSP70A potentially involved in the correct folding of the photosynthetic system-related proteins (D1/D2), preventing aggregation. The photosynthetic activity results demonstrated that overexpression of HSP70A improves non-photochemical quenching (NPQ) activity under high-temperature stress. These results reveal that HSP70A regulates the photosynthetic activity of P. tricornutum under high temperatures. This study not only helps us to understand the photosynthetic activity of marine diatoms to high temperature but also provides a molecular mechanism for HSP70A in P. tricornutum under high-temperature stress.

'Against all floods': plant adaptation to flooding stress and combined abiotic stresses.

Current climate change brings with it a higher frequency of environmental stresses, which occur in combination rather than individually leading to massive crop losses worldwide. In addition to, for example, drought stress (low water availability), also flooding (excessive water) can threaten the plant, causing, among others, an energy crisis due to hypoxia, which is responded to by extensive transcriptional, metabolic and growth-related adaptations. While signalling during flooding is relatively well understood, at least in model plants, the molecular mechanisms of combinatorial flooding stress responses, for example, flooding simultaneously with salinity, temperature stress and heavy metal stress or sequentially with drought stress, remain elusive. This represents a significant gap in knowledge due to the fact that dually stressed plants often show unique responses at multiple levels not observed under single stress. In this review, we (i) consider possible effects of stress combinations from a theoretical point of view, (ii) summarize the current state of knowledge on signal transduction under single flooding stress, (iii) describe plant adaptation responses to flooding stress combined with four other abiotic stresses and (iv) propose molecular components of combinatorial flooding (hypoxia) stress adaptation based on their reported dual roles in multiple stresses. This way, more future emphasis may be placed on deciphering molecular mechanisms of combinatorial flooding stress adaptation, thereby potentially stimulating development of molecular tools to improve plant resilience towards multi-stress scenarios.

Wheat TaNACα18 functions as a positive regulator of high-temperature adaptive responses and improves cell defense machinery.

Global wheat production amounted to >780 MMT during 2022-2023 whose market size are valued at >$128 billion. Wheat is highly susceptible to high-temperature stress (HTS) throughout the life cycle and its yield declines 5-7% with the rise in each degree of temperature. Previously, we reported an array of HTS-response markers from a resilient wheat cv. Unnat Halna and described their putative role in heat acclimation. To complement our previous results and identify the key determinants of thermotolerance, here we examined the cytoplasmic proteome of a sensitive cv. PBW343. The HTS-triggered metabolite reprograming highlighted how proteostasis defects influence the formation of an integrated stress-adaptive response. The proteomic analysis identified several promising HTS-responsive proteins, including a NACα18 protein, designated TaNACα18, whose role in thermotolerance remains unknown. Dual localization of TaNACα18 suggests its crucial functions in the cytoplasm and nucleus. The homodimerization of TaNACα18 anticipated its function as a transcriptional coactivator. The complementation of TaNACα18 in yeast and overexpression in wheat demonstrated its role in thermotolerance across the kingdom. Altogether, our results suggest that TaNACα18 imparts tolerance through tight regulation of gene expression, cell wall remodeling and activation of cell defense responses.

Time of day and genotype sensitivity adjust molecular responses to temperature stress in sorghum.

Sorghum is one of the four major C4 crops that are considered to be tolerant to environmental extremes. Sorghum shows distinct growth responses to temperature stress depending on the sensitivity of the genetic background. About half of the transcripts in sorghum exhibit diurnal rhythmic expressions emphasizing significant coordination with the environment. However, an understanding of how molecular dynamics contribute to genotype-specific stress responses in the context of the time of day is not known. We examined whether temperature stress and the time of day impact the gene expression dynamics in thermo-sensitive and thermo-tolerant sorghum genotypes. We found that time of day is highly influencing the temperature stress responses, which can be explained by the rhythmic expression of most thermo-responsive genes. This effect is more pronounced in thermo-tolerant genotypes, suggesting a stronger regulation of gene expression by the time of day and/or by the circadian clock. Genotypic differences were mostly observed on average gene expression levels, which may be responsible for contrasting sensitivities to temperature stress in tolerant versus susceptible sorghum varieties. We also identified groups of genes altered by temperature stress in a time-of-day and genotype-specific manner. These include transcriptional regulators and several members of the Ca2+ -binding EF-hand protein family. We hypothesize that expression variation of these genes between genotypes along with time-of-day independent regulation may contribute to genotype-specific fine-tuning of thermo-responsive pathways. These findings offer a new opportunity to selectively target specific genes in efforts to develop climate-resilient crops based on their time-of-day and genotype variation responses to temperature stress.

Complete mitochondrial genome assembly of Juglans regia unveiled its molecular characteristics, genome evolution, and phylogenetic implications.

BACKGROUND: The Persian walnut (Juglans regia), an economically vital species within the Juglandaceae family, has seen its mitochondrial genome sequenced and assembled in the current study using advanced Illumina and Nanopore sequencing technology. RESULTS: The 1,007,576 bp mitogenome of J. regia consisted of three circular chromosomes with a 44.52% GC content encoding 39 PCGs, 47 tRNA, and five rRNA genes. Extensive repetitive sequences, including 320 SSRs, 512 interspersed, and 83 tandem repeats, were identified, contributing to genomic complexity. The protein-coding sequences (PCGs) favored A/T-ending codons, and the codon usage bias was primarily shaped by selective pressure. Intracellular gene transfer occurred among the mitogenome, chloroplast, and nuclear genomes. Comparative genomic analysis unveiled abundant structure and sequence variation among J. regia and related species. The results of selective pressure analysis indicated that most PCGs underwent purifying selection, whereas the atp4 and ccmB genes had experienced positive selection between many species pairs. In addition, the phylogenetic examination, grounded in mitochondrial genome data, precisely delineated the evolutionary and taxonomic relationships of J. regia and its relatives. We identified a total of 539 RNA editing sites, among which 288 were corroborated by transcriptome sequencing data. Furthermore, expression profiling under temperature stress highlighted the complex regulation pattern of 28 differently expressed PCGs, wherein NADH dehydrogenase and ATP synthase genes might be critical in the mitochondria response to cold stress. CONCLUSIONS: Our results provided valuable molecular resources for understanding the genetic characteristics of J. regia and offered novel perspectives for population genetics and evolutionary studies in Juglans and related woody species.

Identification and expression analysis of CCCH gene family and screening of key low temperature stress response gene CbuC3H24 and CbuC3H58 in Catalpa bungei.

Catalpa bungei, a tree indigenous to China, is renowned for its superior timber quality and as an ornamental in horticulture. To promote the cultivation of C. bungei in cold regions and expand its distribution, enhancing its cold tolerance is essential. The CCCH gene family is widely involved in plant growth, development, and expression under stress conditions, including low-temperature stress. However, a comprehensive identification and analysis of these genes have not yet been conducted. This study aims to identify key cold-tolerance-related genes within the CCCH gene family of C. bungei, providing the necessary theoretical support for its expansion in cold regions. In this study, 61 CCCH genes within C. bungei were identified and characterized. Phylogenetic assessment divided these genes into 9 subfamilies, with 55 members mapped across 16 chromosomes. The analysis of gene structures and protein motifs indicated that members within the same subfamily shared similar exon/intron distribution and motif patterns, supporting the phylogenetic classification. Collinearity analysis suggested that segmental duplications have played a significant role in the expansion of the C. bungei CCCH gene family. Notably, RNA sequencing analysis under 4 °C cold stress conditions identified CbuC3H24 and CbuC3H58 as exhibiting the most significant responses, highlighting their importance within the CCCH zinc finger family in response to cold stress. The findings of this study lay a theoretical foundation for further exploring the mechanisms of cold tolerance in C. bungei, providing crucial insights for its cultivation in cold regions.

Identification of transient receptor potential channel genes from the swimming crab, Portunus Trituberculatus, and their expression profiles under acute temperature stress.

BACKGROUND: Temperature is an important environment factor that is critical to the survival and growth of crustaceans. However, the mechanisms by which crustaceans detect changes in temperature are still unclear. The transient receptor potential (TRP) channels are non-selective cation channels well known for properties in temperature sensation. However, comprehensive understandings on TRP channels as well as their temperature sensing functions are still lacking in crustaceans. RESULTS: In this study, a total of 26 TRP genes were identified in the swimming crab, Portunus trituberculatus, which can be classified into TRPA, TRPC, TRPP, TRPM, TRPML, TRPN and TRPV. Tissue expression analysis revealed a wide distribution of these TRP genes in P. trituberculatus, and antennules, neural tissues, and ovaries were the most commonly expressed tissues. To investigate the responsiveness of TRP genes to the temperature change, 18 TRPs were selected to detect their expression after high and low temperature stress. The results showed that 12 TRPs showed induced gene expression in both high and low temperature groups, while 3 were down-regulated in the low temperature group, and 3 showed no change in expression in either group. CONCLUSIONS: This study characterized the TRP family genes in P. trituberculatus, and explored their involvement in response to temperature stress. Our results will enhance overall understanding of crustacean TRP channels and their possible functions.

Discovery and demonstration of the temperature stress response functions of Dermatophagoides farinae proteins 1 and 2.

BACKGROUND: Dermatophagoides farinae proteins (DFPs) are abundantly expressed in D. farinae; however, their functions remain unknown. Our previous transcriptome sequencing analyses revealed that the basal expression of DFP1 and DFP2 in D. farinae was high and, more importantly, upregulated under temperature stress. Therefore, DFPs were speculated to exert a temperature stress response function. RESULTS: Real-time quantitative polymerase chain reaction detection revealed that both DFP1 and DFP2 were significantly upregulated under temperature stress. Particularly, DFP1 was upregulated under cold stress. Electrophoresis of D. farinae total proteins revealed an increased abundance of DFP1 and DFP2 (40-55 kDa bands) under temperature stress, which was corroborated by the mass spectrometry results. After silencing DFP1 and DFP2 further, temperature stress led to decreases in gene expression and survival rates. Moreover, DFP1 was identified as the upstream regulator of DFP2. CONCLUSION: This study highlights the temperature stress response functions of DFP1 and DFP2 at the mRNA and protein levels. These results provide important insights for applying DFP1 and DFP2 as potential target genes for the molecular prevention and control of D. farinae to prevent allergic diseases. The newly established methods provide methodological guidance for the study of genes with unknown functions in mites.

Genome-wide identification of polyamine metabolism and ethylene synthesis genes in Chenopodium quinoa Willd. and their responses to low-temperature stress.

BACKGROUND: Quinoa (Chenopodium quinoa Willd.) is valued for its nutritional richness. However, pre-harvest sprouting poses a significant threat to yield and grain quality. This study aims to enhance our understanding of pre-harvest sprouting mitigation strategies, specifically through delayed sowing and avoiding rainy seasons during quinoa maturation. The overarching goal is to identify cold-resistant varieties and unravel the molecular mechanisms behind the low-temperature response of quinoa. We employed bioinformatics and genomics tools for a comprehensive genome-wide analysis of polyamines (PAs) and ethylene synthesis gene families in quinoa under low-temperature stress. RESULTS: This involved the identification of 37 PA biosynthesis and 30 PA catabolism genes, alongside 227 ethylene synthesis. Structural and phylogenetic analyses showcased conserved patterns, and subcellular localization predictions indicated diverse cellular distributions. The results indicate that the PA metabolism of quinoa is closely linked to ethylene synthesis, with multiple genes showing an upregulation in response to cold stress. However, differential expression within gene families suggests a nuanced regulatory network. CONCLUSIONS: Overall, this study contributes valuable insights for the functional characterization of the PA metabolism and ethylene synthesis of quinoa, which emphasize their roles in plant low-temperature tolerance and providing a foundation for future research in this domain.

The rhizobacterial Priestia megaterium strain SH-19 mitigates the hazardous effects of heat stress via an endogenous secondary metabolite elucidation network and molecular regulation signalling.

Global warming is a leading environmental stress that reduces plant productivity worldwide. Several beneficial microorganisms reduce stress; however, the mechanism by which plant-microbe interactions occur and reduce stress remains to be fully elucidated. The aim of the present study was to elucidate the mutualistic interaction between the plant growth-promoting rhizobacterial strain SH-19 and soybeans of the Pungsannamul variety. The results showed that SH-19 possessed several plant growth-promoting traits, such as the production of indole-3-acetic acid, siderophore, and exopolysaccharide, and had the capacity for phosphate solubilisation. The heat tolerance assay showed that SH-19 could withstand temperatures up to 45 °C. The strain SH-19 was identified as P. megaterium using the 16S ribosomal DNA gene sequence technique. Inoculation of soybeans with SH-19 improved seedling characteristics under high-temperature stress. This may be due to an increase in the endogenous salicylic acid level and a decrease in the abscisic acid level compared with the negative control group. The strain of SH-19 increased the activity of the endogenous antioxidant defense system, resulting in the upregulation of GSH (44.8%), SOD (23.1%), APX (11%), and CAT (52.6%). Furthermore, this study involved the transcription factors GmHSP, GmbZIP1, and GmNCED3. The findings showed upregulation of the two transcription factors GmbZIP1 (17%), GmNCED3 (15%) involved in ABA biosynthesis and induced stomatal regulation, similarly, a downregulation of the expression pattern of GmHSP by 25% was observed. Overall, the results of this study indicate that the strain SH-19 promotes plant growth, reduces high-temperature stress, and improves physiological parameters by regulating endogenous phytohormones, the antioxidant defense system, and genetic expression. The isolated strain (SH-19) could be commercialized as a biofertilizer.

Comparative transcriptomic and metabolomic analyses provide insights into the responses to high temperature stress in Alfalfa (Medicago sativa L.).

High temperature stress is one of the most severe forms of abiotic stress in alfalfa. With the intensification of climate change, the frequency of high temperature stress will further increase in the future, which will bring challenges to the growth and development of alfalfa. Therefore, untargeted metabolomic and RNA-Seq profiling were implemented to unravel the possible alteration in alfalfa seedlings subjected to different temperature stress (25 ℃, 30 ℃, 35 ℃, 40 ℃) in this study. Results revealed that High temperature stress significantly altered some pivotal transcripts and metabolites. The number of differentially expressed genes (DEGs) markedly up and down-regulated was 1876 and 1524 in T30_vs_CK, 2, 815 and 2667 in T35_vs_CK, and 2115 and 2, 226 in T40_vs_CK, respectively. The number for significantly up-regulated and down-regulated differential metabolites was 173 and 73 in T30_vs_CK, 188 and 57 in T35_vs_CK, and 220 and 66 in T40_vs_CK, respectively. It is worth noting that metabolomics and transcriptomics co-analysis characterized enriched in plant hormone signal transduction (ko04705), glyoxylate and dicarboxylate metabolism (ko00630), from which some differentially expressed genes and differential metabolites participated. In particular, the content of hormone changed significantly under T40 stress, suggesting that maintaining normal hormone synthesis and metabolism may be an important way to improve the HTS tolerance of alfalfa. The qRT-PCR further showed that the expression pattern was similar to the expression abundance in the transcriptome. This study provides a practical and in-depth perspective from transcriptomics and metabolomics in investigating the effects conferred by temperature on plant growth and development, which provided the theoretical basis for breeding heat-resistant alfalfa.

Muti-omics revealed the mechanisms of MT-conferred tolerance of Elymus nutans Griseb. to low temperature at XiZang.

BACKGROUND: Low temperature seriously limited the development of grass and crops in plateau. Thus, it is urgent to develop an effective strategy for improving the plant cold tolerance and elucidate the underlying mechanisms. RESULTS: We found that MT alleviated the effects of cold stress on suppressing ENG growth, then improved cold tolerance of ENG. Integration of transcriptome and metabolome profiles showed that both cold exposure (TW) and MT reprogrammed the transcription pattern of galactose and flavonoids biosynthesis, leading to changes in compositions of soluble sugar and flavonoids in ENG. Additionally, TW inhibited the photosynthesis, and destroyed the antioxidant system of ENG, leading to accumulation of oxidant radicals represented by MDA. By contrast, MT promoted activities of antioxidant enzymes and flavonoid accumulation in ENG under cold condition, then reduced the MDA content and maintained normal expression of photosynthesis-related genes in ENG even under TW. Importantly, MT mainly enhanced cold tolerance of ENG via activating zeatin synthesis to regulate flavonoid biosynthesis in vivo. Typically, WRKY11 was identified to regulate MT-associated zeatin synthesis in ENG via directly binding on zeatin3 promoter. CONCLUSIONS: MT could enhance ENG tolerance to cold stress via strengthening antioxidant system and especially zeatin synthesis to promote accumulation of flavonoids in ENG. Thus, our research gain insight into the global mechanisms of MT in promoting cold tolerance of ENG, then provided guidance for protecting plant from cold stress in plateau.

Overexpression of PavHIPP16 from Prunus avium enhances cold stress tolerance in transgenic tobacco.

BACKGROUND: The heavy metal-associated isoprenylated plant protein (HIPP) is an important regulatory element in response to abiotic stresses, especially playing a key role in low-temperature response. RESULTS: This study investigated the potential function of PavHIPP16 up-regulated in sweet cherry under cold stress by heterologous overexpression in tobacco. The results showed that the overexpression (OE) lines' growth state was better than wild type (WT), and the germination rate, root length, and fresh weight of OE lines were significantly higher than those of WT. In addition, the relative conductivity and malondialdehyde (MDA) content of the OE of tobacco under low-temperature treatment were substantially lower than those of WT. In contrast, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) activities, hydrogen peroxide (H2O2), proline, soluble protein, and soluble sugar contents were significantly higher than those of WT. Yeast two-hybrid assay (Y2H) and luciferase complementation assay verified the interactions between PavbHLH106 and PavHIPP16, suggesting that these two proteins co-regulated the cold tolerance mechanism in plants. The research results indicated that the transgenic lines could perform better under low-temperature stress by increasing the antioxidant enzyme activity and osmoregulatory substance content of the transgenic plants. CONCLUSIONS: This study provides genetic resources for analyzing the biological functions of PavHIPPs, which is important for elucidating the mechanisms of cold resistance in sweet cherry.

Integration analysis of miRNA-mRNA pairs between two contrasting genotypes reveals the molecular mechanism of jujube (Ziziphus jujuba Mill.) response to high-temperature stress.

With global warming, high temperature (HT) has become one of the most common abiotic stresses resulting in significant crop yield losses, especially for jujube (Ziziphus jujuba Mill.), an important temperate economic crop cultivated worldwide. This study aims to explore the coping mechanism of jujube to HT stress at the transcriptional and post-transcriptional levels, including identifying differentially expressed miRNAs and mRNAs as well as elucidating the critical pathways involved. High-throughput sequencing analyses of miRNA and mRNA were performed on jujube leaves, which were collected from "Fucumi" (heat-tolerant) and "Junzao" (heat-sensitive) cultivars subjected to HT stress (42 °C) for 0, 1, 3, 5, and 7 days, respectively. The results showed that 45 known miRNAs, 482 novel miRNAs, and 13,884 differentially expressed mRNAs (DEMs) were identified. Among them, integrated analysis of miRNA target genes prediction and mRNA-seq obtained 1306 differentially expressed miRNAs-mRNAs pairs, including 484, 769, and 865 DEMIs-DEMs pairs discovered in "Fucuimi", "Junzao" and two genotypes comparative groups, respectively. Furthermore, functional enrichment analysis of 1306 DEMs revealed that plant-pathogen interaction, starch and sucrose metabolism, spliceosome, and plant hormone signal transduction were crucial pathways in jujube leaves response to HT stress. The constructed miRNA-mRNA network, composed of 20 DEMIs and 33 DEMs, displayed significant differently expressions between these two genotypes. This study further proved the regulatory role of miRNAs in the response to HT stress in plants and will provide a theoretical foundation for the innovation and cultivation of heat-tolerant varieties.

Genome-wide identification and comprehensive analysis of the AP2/ERF gene family in Prunus sibirica under low-temperature stress.

BACKGROUND: AP2/ERF transcription factors are involved in the regulation of growth, development, and stress response in plants. Although the gene family has been characterized in various species, such as Oryza sativa, Arabidopsis thaliana, and Populus trichocarpa, studies on the Prunus sibirica AP2/ERF (PsAP2/ERF) gene family are lacking. In this study, PsAP2/ERFs in P. sibirica were characterized by genomic and transcriptomic analyses. RESULTS: In the study, 112 PsAP2/ERFs were identified and categorized into 16 subfamilies. Within each subfamily, PsAP2/ERFs exhibited similar exon-intron structures and motif compositions. Additionally, 50 pairs of segmentally duplicated genes were identified within the PsAP2/ERF gene family. Our experimental results showed that 20 PsAP2/ERFs are highly expressed in leaves, roots, and pistils under low-temperature stress conditions. Among them, the expression of PsAP2/ERF21, PsAP2/ERF56 and PsAP2/ERF88 was significantly up-regulated during the treatment period, and it was hypothesised that members of the PsAP2/ERF family play an important role inlow temperature stress tolerance. CONCLUSIONS: This study improves our understanding of the molecular basis of development and low-temperature stress response in P. sibirica and provides a solid scientific foundation for further functional assays and evolutionary analyses of PsAP2/ERFs.

The role of cis-zeatin in enhancing high-temperature resistance and fucoxanthin biosynthesis in Phaeodactylum tricornutum.

Phaeodactylum tricornutum a prominent source of industrial fucoxanthin production, faces challenges in its application due to its tolerance to high-temperature environments. This study investigates the physiological responses of P. tricornutum to high-temperature stress and its impact on fucoxanthin content, with a specific focus on the role of cis-zeatin. The results reveal that high-temperature stress inhibits P. tricornutum's growth and photosynthetic activity, leading to a decrease in fucoxanthin content. Transcriptome analysis shows that high temperature suppresses the expression of genes related to photosynthesis (e.g., psbO, psbQ, and OEC) and fucoxanthin biosynthesis (e.g., PYS, PDS1, and PSD2), underscoring the negative effects of high temperature on P. tricornutum. Interestingly, genes associated with cis-zeatin biosynthesis and cytokinesis signaling pathways exhibited increased expression under high-temperature conditions, indicating a potential role of cis-zeatin signaling in response to elevated temperatures. Content measurements confirm that high temperature enhances cis-zeatin content. Furthermore, the exogenous addition of cytokinesis mimetics or inhibitors significantly affected P. tricornutum's high-temperature resistance. Overexpression of the cis-zeatin biosynthetic enzyme gene tRNA DMATase enhanced P. tricornutum's resistance to high-temperature stress, while genetic knockout of tRNA DMATase reduced its resistance to high temperatures. Therefore, this research not only uncovers a novel mechanism for high-temperature resistance in P. tricornutum but also offers a possible alga species that can withstand high temperatures for the industrial production of fucoxanthin, offering valuable insights for practical utilization.IMPORTANCEThis study delves into Phaeodactylum tricornutum's response to high-temperature stress, specifically focusing on cis-zeatin. We uncover inhibited growth, reduced fucoxanthin, and significant cis-zeatin-related gene expression under high temperatures, highlighting potential signaling mechanisms. Crucially, genetic engineering and exogenous addition experiments confirm that the change in cis-zeatin levels could influence P. tricornutum's resistance to high-temperature stress. This breakthrough deepens our understanding of microalgae adaptation to high temperatures and offers an innovative angle for industrial fucoxanthin production. This research is a pivotal step toward developing heat-resistant microalgae for industrial use.

Physiology, gene expression, and epiphenotype of two Dianthus broteri polyploid cytotypes under temperature stress.

Increasing evidence supports a major role for abiotic stress response in the success of plant polyploids, which usually thrive in harsh environments. However, understanding the ecophysiology of polyploids is challenging due to interactions between genome doubling and natural selection. Here, we investigated physiological responses, gene expression, and the epiphenotype of two related Dianthus broteri cytotypes-with different genome duplications (4× and 12×) and evolutionary trajectories-to short extreme temperature events (42/28 °C and 9/5 °C). The 12× cytotype showed higher expression of stress-responsive genes (SWEET1, PP2C16, AI5L3, and ATHB7) and enhanced gas exchange compared with 4×. Under heat stress, both ploidies had greatly impaired physiological performance and altered gene expression, with reduced cytosine methylation. However, the 12× cytotype exhibited remarkable physiological tolerance (maintaining gas exchange and water status via greater photochemical integrity and probably enhanced water storage) while down-regulating PP2C16 expression. Conversely, 4× D. broteri was susceptible to thermal stress despite prioritizing water conservation, showing signs of non-stomatal photosynthetic limitations and irreversible photochemical damage. This cytotype also presented gene-specific expression patterns under heat, up-regulating ATHB7. These findings provide insights into divergent stress response strategies and physiological resistance resulting from polyploidy, highlighting its widespread influence on plant function.

Vitamin C as a functional enhancer in the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab, Scylla paramamosain.

This experiment was conducted to explore the effects of dietary vitamin C supplementation on non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab (Scylla paramamosain). Mud crabs with an initial weight of 14.67 ± 0.13 g were randomly divided into 6 treatments and fed diets with 0.86 (control), 44.79, 98.45, 133.94, 186.36 and 364.28 mg/kg vitamin C, respectively. The experiment consisted of 6 treatments, each treatment was designed with 4 replicates and each replicate was stocked with 8 crabs. After 42 days of feeding experiment, 2 crabs were randomly selected from each replicate, and a total of 8 crabs in each treatment were carried out 72 h low-temperature challenge experiment. The results showed that crabs fed diets with 186.36 and 364.28 mg/kg vitamin C significantly improved the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemolymph and hepatopancreas (P < 0.05). Crabs fed diet with 133.94 mg/kg vitamin C significantly decreased the concentration of nitric oxide (NO) and the activity of nitric oxide synthase (NOS) in hemolymph (P < 0.05). Diet with 133.94 mg/kg vitamin C was improved the activity of polyphenol oxidase (PPO) and the concentration of albumin (ALB) in hemolymph. Crabs fed diet with 133.94 mg/kg vitamin C showed lower concentration of malondialdehyde (MDA) in hemolymph and hepatopancreas than those fed the other diets. Meanwhile, crabs fed diet with 98.45 mg/kg vitamin C showed higher activity of total superoxide dismutase (T-SOD) in hemolymph, and crabs fed diet with 133.94 mg/kg vitamin C showed higher activity of T-SOD in hepatopancreas. Crabs fed diet with 186.36 mg/kg vitamin C significantly decreased the concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GSH-PX) in hepatopancreas (P < 0.05). In normal temperature, crabs fed diets with 133.94 mg/kg vitamin C significantly up-regulated the expression levels of gpx (glutathione peroxidase) and trx (thioredoxin) in hepatopancreas compared with the control treatment (P < 0.05). The highest expression levels of relish, il16 (interleukin 16), caspase 2 (caspase 2), p38 mapk (p38 mitogen-activated protein kinases) and bax (bcl-2 associated x protein) in hepatopancreas were found at crabs fed control diet (P < 0.05). Moreover, crabs fed diet with 133.94 mg/kg vitamin C showed higher expression levels of alf-3 (anti-lipopolysaccharide factor 3) and bcl-2 (B-cell lymphoma 2) in hepatopancreas than those fed the other diets (P < 0.05). Under low-temperature stress, crabs fed diet with 133.94 mg/kg vitamin C significantly improved the expression levels of hsp90 (heat shock protein 90), cat (catalase), gpx, prx (thioredoxin peroxidase) and trx in hepatopancreas (P < 0.05). In addition, dietary with 133.94 vitamin C significantly up-regulated the expression levels of alf-3 and bcl-2 (P < 0.05). Based on two slope broken-line regression analysis of activity of PPO against the dietary vitamin C level, the optimal dietary vitamin C requirement was estimated to be 144.81 mg/kg for juvenile mud crab. In conclusion, dietary 133.94-144.81 mg/kg vitamin C significantly improved the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab.