Overexpression of wheat transcription factor (TaHsfA6b) provides thermotolerance in barley

Application of Zinc Oxide Nanoparticles to Mitigate Cadmium Toxicity: Mechanisms and Future Prospects

Cadmium (Cd), as the most prevalent heavy metal contaminant poses serious risks to plants, humans, and the environment. The ubiquity of this toxic metal is continuously increasing due to the rapid discharge of industrial and mining effluents and the excessive use of chemical fertilizers. Nanoparticles (NPs) have emerged as a novel strategy to alleviate Cd toxicity. Zinc oxide nanoparticles (ZnO-NPs) have become the most important NPs used to mitigate the toxicity of abiotic stresses and improve crop productivity. The plants quickly absorb Cd, which subsequently disrupts plant physiological and biochemical processes and increases the production of reactive oxygen species (ROS), which causes the oxidation of cellular structures and significant growth losses. Besides this, Cd toxicity also disrupts leaf osmotic pressure, nutrient uptake, membrane stability, chlorophyll synthesis, and enzyme activities, leading to a serious reduction in growth and biomass productivity. Though plants possess an excellent defense mechanism to counteract Cd toxicity, this is not enough to counter higher concentrations of Cd toxicity. Applying Zn-NPs has proven to have significant potential in mitigating the toxic effects of Cd. ZnO-NPs improve chlorophyll synthesis, photosynthetic efficiency, membrane stability, nutrient uptake, and gene expression, which can help to counter toxic effects of Cd stress. Additionally, ZnO-NPs also help to reduce Cd absorption and accumulation in plants, and the complex relationship between ZnO-NPs, osmolytes, hormones, and secondary metabolites plays an important role in Cd tolerance. Thus, this review concentrates on exploring the diverse mechanisms by which ZnO nanoparticles can alleviate Cd toxicity in plants. In the end, this review has identified various research gaps that need addressing to ensure the promising future of ZnO-NPs in mitigating Cd toxicity. The findings of this review contribute to gaining a deeper understanding of the role of ZnO-NPs in combating Cd toxicity to promote safer and sustainable crop production by remediating Cd-polluted soils. This also allows for the development of eco-friendly approaches to remediate Cd-polluted soils to improve soil fertility and environmental quality.

Heat-stress-responsive HvHSFA2e gene regulates the heat and drought tolerance in barley through modulation of phytohormone and secondary metabolic pathways

KEY MESSAGE

The heat stress transcription factor HSFA2e regulates both temperature and drought response via hormonal and secondary metabolism alterations. High temperature and drought are the primary yield-limiting environmental constraints for staple food crops. Heat shock transcription factors (HSF) terminally regulate the plant abiotic stress responses to maintain growth and development under extreme environmental conditions. HSF genes of subclass A2 predominantly express under heat stress (HS) and activate the transcriptional cascade of defense-related genes. In this study, a highly heat-inducible HSF, HvHSFA2e was constitutively expressed in barley (Hordeum vulgare L.) to investigate its role in abiotic stress response and plant development. Transgenic barley plants displayed enhanced heat and drought tolerance in terms of increased chlorophyll content, improved membrane stability, reduced lipid peroxidation, and less accumulation of ROS in comparison to wild-type (WT) plants. Transcriptome analysis revealed that HvHSFA2e positively regulates the expression of abiotic stress-related genes encoding HSFs, HSPs, and enzymatic antioxidants, contributing to improved stress tolerance in transgenic plants. The major genes of ABA biosynthesis pathway, flavonoid, and terpene metabolism were also upregulated in transgenics. Our findings show that HvHSFA2e-mediated upregulation of heat-responsive genes, modulation in ABA and flavonoid biosynthesis pathways enhance drought and heat stress tolerance.

Zinc oxide nanoparticles alleviate cadmium toxicity and promote tolerance by modulating programmed cell death in alfalfa (Medicago sativa L.)

Cadmium (Cd) can induce programmed cell death (PCD) and zinc oxide nanoparticles (ZnO NPs) effectively alleviate Cd stress. However, the mechanisms of ZnO NPs-mediated Cd detoxification in alfalfa (Medicago sativa L.) are limited. The pot experiment was conducted with Cd soil (19.2 mg kg-1) and foliar ZnO NPs (100 mg L-1) on alfalfa. The results showed that Cd reduced shoot height and biomass, and accumulated reactive oxygen species (ROS), resulting in oxidative stress and further PCD (plasmolysis, cytosolic and nuclear condensation, subcellular organelle swelling, and cell death). ZnO NPs positively regulated the antioxidant system, cell membrane stability, ultrastructure, osmotic homeostasis, and reduced PCD, indicating a multi-level coordination for the increased Cd tolerance. ZnO NPs up-regulated the activity and expression of antioxidant enzymes and regulated PCD-related genes to scavenge ROS and mitigate PCD caused by Cd. The genes related to ZnO NPs-mediated Cd detoxification were significantly enriched in cell death and porphyrin and chlorophyll metabolism. Overall, it elucidates the molecular basis of ZnO NPs-mediated Cd-tolerance by promoting redox and osmotic homeostasis, maintaining cellular ultrastructure, reducing Cd content, and attenuating Cd-induced PCD. it provides a promising application of ZnO NPs to mitigate Cd phytotoxicity and the related cellular and biochemical mechanisms. ENVIRONMENTAL IMPLICATION: Cd, one of the most toxic heavy metals, has caused serious environmental pollution. ZnO NPs can effectively alleviate Cd stress on plants and the environment. This study revealed that foliar-applied ZnO NPs alleviate Cd toxicity by mitigating the oxidative damage and regulating Cd-induced PCD via morphological, physiological, and transcriptomic levels. The findings elucidated the molecular basis of ZnO NPs-mediated Cd tolerance by promoting osmotic and redox homeostasis, reducing Cd content and lipid peroxidation, attenuating Cd-induced PCD features, and altering PCD-related genes in alfalfa. The study laid a theoretical foundation for the safe production of alfalfa under Cd pollution.

Physiological and RNA-Seq Analyses on Exogenous Strigolactones Alleviating Drought by Improving Antioxidation and Photosynthesis in Wheat (Triticum aestivum L.)

Drought poses a significant challenge to global wheat production, and the application of exogenous phytohormones offers a convenient approach to enhancing drought tolerance of wheat. However, little is known about the molecular mechanism by which strigolactones (SLs), newly discovered phytohormones, alleviate drought stress in wheat. Therefore, this study is aimed at elucidating the physiological and molecular mechanisms operating in wheat and gaining insights into the specific role of SLs in ameliorating responses to the stress. The results showed that SLs application upregulated the expression of genes associated with the antioxidant defense system (Fe/Mn-SOD, PER1, PER22, SPC4, CAT2, APX1, APX7, GSTU6, GST4, GOR, GRXC1, and GRXC15), chlorophyll biogenesis (CHLH, and CPX), light-harvesting chlorophyll A-B binding proteins (WHAB1.6, and LHC Ib-21), electron transfer (PNSL2), E3 ubiquitin-protein ligase (BB, CHIP, and RHY1A), heat stress transcription factor (HSFA1, HSFA4D, and HSFC2B), heat shock proteins (HSP23.2, HSP16.9A, HSP17.9A, HSP21, HSP70, HSP70-16, HSP70-17, HSP70-8, HSP90-5, and HSP90-6), DnaJ family members (ATJ1, ATJ3, and DJA6), as well as other chaperones (BAG1, CIP73, CIPB1, and CPN60I). but the expression level of genes involved in chlorophyll degradation (SGR, NOL, PPH, PAO, TIC55, and PTC52) as well as photorespiration (AGT2) was found to be downregulated by SLs priming. As a result, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced, and chlorophyll content and photosynthetic rate were increased, which indicated the alleviation of drought stress in wheat. These findings demonstrated that SLs alleviate drought stress by promoting photosynthesis through enhancing chlorophyll levels, and by facilitating ROS scavenging through modulation of the antioxidant system. The study advances understandings of the molecular mechanism underlying SLs-mediated drought alleviation and provides valuable insights for implementing sustainable farming practice under water restriction.

An insight into Pisum sativum HSF gene family-Genome-wide identification, phylogenetic, expression, and analysis of transactivation potential of pea heat shock transcription factor

Field pea (Pisum sativum L, 2n = 14) is a popular temperate legume with high economic value. Heat shock factors (HSFs) are the core element in the regulatory mechanism of heat stress responses. HSFs in pea (P. sativum) have not been characterized and their role remains unclear in different abiotic stresses. To address this knowledge gap, the current study aimed to characterize the HSF gene family in pea. We identified 38 PsHsf members in P. sativum, which are distributed on the seven chromosomes, and based on phylogenetic analysis, we classified them into three representative classes i.e. A, B, and C. Conserved motif and gene structure analysis confirmed a high degree of similarity among the members of the same class. Additionally, identified cis-acting regulatory elements (CAREs) related to abiotic responses, development, growth, and hormone signaling provides crucial insights into the regulatory mechanisms of PsHsfs. Our research revealed instances of gene duplication in PsHsf gene family, suggesting that this mechanism could be driving the expansion of the PsHsf gene family. Moreover, Expression analysis of PsHsfs exhibited upregulation under heat stress (HS), salt stress (SS), and drought stress (DS) showing their phenomenal role in stress conditions. PsHsfs protein interaction network suggested their involvement in stress-responsive mechanisms. Further transactivation potential was checked for spliced variant of PsHsfA2a (PsHsfA2aI, PsHsfA2aII, and PsHsfA2aIII), PsHsfA3, PsHsfA6b, PsHsfA9, PsHsfB1a, and PsHsfB2a. Overall, these findings provide valuable insight into the evolutionary relationship of PsHsf gene family and their role in abiotic stress responses.

Ectopic overexpression of TaHsfA5 promotes thermomorphogenesis in Arabidopsis thaliana and thermotolerance in Oryza sativa

Heat stress transcription factors (Hsfs) play an important role in regulating the heat stress response in plants. Among the Hsf family members, the group A members act upstream in initiating the response upon sensing heat stress and thus, impart thermotolerance to the plants. In the present study, wheat HsfA5 (TaHsfA5) was found to be one of the Hsfs, which was upregulated both in heat stress and during the recovery period after the stress. TaHsfA5 was found to interact with TaHsfA3 and TaHsfA4, both of which are known to positively regulate the heat stress-responsive genes. Apart from these, TaHsfA5 also interacted with TaHSBP2 protein, whose role has been implicated in attenuating the heat stress response. Further, its heterologous overexpression in Arabidopsis and Oryza sativa promoted thermotolerance in these plants. This indicated that TaHsfA5 positively regulated the heat stress response. Interestingly, the TaHsfA5 overexpression Arabidopsis plants when grown at warm temperatures showed  a hyper-thermomorphogenic response in comparison to the wild-type plants. This was found to be consistent with the higher expression of PIF4 and its target auxin-responsive genes in these transgenics in contrast to the wild-type plants. Thus, these results suggest the involvement of TaHsfA5 both in the heat stress response as well as in the thermomorphogenic response in plants.

Transcriptome reveals the exposure effects of CeO2 nanoparticles on pakchoi (Brassica chinensis L.) photosynthesis

In this study, soil-grown pakchoi after 2 weeks seedling cultivation were exposed to CeO₂ nanoparticles (CeO₂ NPs) at 0.7, 7, 70, and 350 mg kg^-1 for 30 days. Results showed that chlorophyll content and photosynthetic assimilation rate were decreased significantly under all treatments with the largest decrease of 34.16% (0.7 mg kg^-1 CeO₂ NPs), however, sub-stomatal CO₂ was increased dramatically under low dose of CeO₂ NPs (0.7 mg kg^-1). There were 4576, 3548, 2787, and 2514 genes up/down regulated significantly by 0.7, 7, 70, and 350 mg kg^-1 CeO₂ NPs, respectively, and 767 genes affected under all treatments. In addition, 0.7 mg kg^-1 CeO₂ NPs up-regulated 10 chlorophyll synthesis genes, 20 photosynthesis genes, and 10 carbon fixation enzyme genes; while 350 mg kg^-1 CeO₂ NPs down-regulated 5 photosynthesis genes and 28 auxin-activated genes. Among the key genes of photosynthesis, Ferredoxin-NADP reductase (PetH) was upregulated in 0.7, 7 and 70 mg kg^-1 treatments, while Photosystem II lipoprotein (Psb27) was downregulated under 7, 70 and 350 mg kg^-1 treatments. Top 20 metabolic pathways affected by CeO₂ NPs including plant hormone, amino acids, and glutathione, and carbon metabolism These results provide information about utilizing CeO₂ NPs more safely and effectively in the future.

Comparison of Gene Expression Changes in Three Wheat Varieties with Different Susceptibilities to Heat Stress Using RNA-Seq Analysis

Wheat is highly susceptible to heat stress, which significantly reduces grain yield. In this study, we used RNA-seq technology to analyze the transcript expression at three different time-points after heat treatment in three cultivars differing in their susceptibility to heat stress: Jopum, Keumkang, and Olgeuru. A total of 11,751, 8850, and 14,711; 10,959, 7946, and 14,205; and 22,895, 13,060, and 19,408 differentially-expressed genes (log2 fold-change > 1 and FDR (padj) < 0.05) were identified in Jopum, Keumkang, and Olgeuru in the control vs. 6-h, in the control vs. 12-h, and in the 6-h vs. 12-h heat treatment, respectively. Functional enrichment analysis showed that the biological processes for DEGs, such as the cellular response to heat and oxidative stress—and including the removal of superoxide radicals and the positive regulation of superoxide dismutase activity—were significantly enriched among the three comparisons in all three cultivars. Furthermore, we investigated the differential expression patterns of reactive oxygen species (ROS)-scavenging enzymes, heat shock proteins, and heat-stress transcription factors using qRT-PCR to confirm the differences in gene expression among the three varieties under heat stress. This study contributes to a better understanding of the wheat heat-stress response at the early growth stage and the varietal differences in heat tolerance.

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

BACKGROUND

Heat shock transcription factors (Hsfs) are highly conserved among eukaryote and always play vital role in plant stress responses. Whereas, function and mechanism of Hsfs in maize are limited.

RESULTS

In this study, an HSF gene ZmHsf11, a member of class B Hsfs, was cloned from maize, and it was up-regulated under heat treatment. ZmHsf11 was a nuclear protein with no transcriptional autoactivation activity in yeast. Overexpression of ZmHsf11 gene in Arabidopsis and rice significantly reduced the survival rate under heat shock treatment and decreased ABA sensitivity of transgenic plants. Under heat stress, transgenic rice accumulated more H₂O₂, increased cell death, and decreased proline content compared with wild type. In addition, RT-qPCR analysis revealed that ZmHsf11 negatively regulated some oxidative stress-related genes APX2, DREB2A, HsfA2e, NTL3, GR and HSP17 under heat stress treatment.

CONCLUSIONS

Our results indicate that ZmHsf11 decreases plant tolerance to heat stress by negatively regulating the expression of oxidative stress-related genes, increasing ROS levels and decreasing proline content. It is a negative regulator involved in high temperature stress response.

AcCIPK5, a pineapple CBL-interacting protein kinase, confers salt, osmotic and cold stress tolerance in transgenic Arabidopsis

Plant-specific calcineurin B-like proteins (CBLs) and their interacting kinases, CBL-interacting protein kinases (CIPKs) module, are essential for dealing with various biotic and abiotic stress. The kinases (CIPKs) of this module have been well studied in several plants; however, the information about pineapple CIPKs remains limited. To understand how CIPKs function against environmental cues in pineapple, the CIPK5 gene of pineapple was cloned and characterized. The phylogenetic analyses revealed that AcCIPK5 is homologous to the CIPK12 of Arabidopsis and other plant species. Quantitative real-time PCR (qRT-PCR) analysis revealed that AcCIPK5 responds to multiple stresses, including osmotic, salt stress, heat and cold. Under optimal conditions, AcCIPK5 gets localized to the cytoplasm and cell membrane. The ectopic expression of AcCIPK5 in Arabidopsis improved the germination under osmotic and salt stress. Furthermore, AcCIPK5 positively regulated osmotic, drought, salt and cold tolerance and negatively regulated heat and fungal stress in Arabidopsis. Besides, the expression of AcCIPK impacted ABA-related genes and ROS homeostasis. Overall, the present study demonstrates that AcCIPK5 contributes to multiple stress tolerance and has the potential to be utilized in the development of stress-tolerant crops.

Isolation and characterization of AaZFP1, a C2H2 zinc finger protein that regulates the AaIPPI1 gene involved in artemisinin biosynthesis in Artemisia annua

AaZFP1, a C2H2-type transcription factor, was found to bind the AGT-N1-10-AGT box of AaIPPI1pro and activate the expression of AaIPPI1 involved in artemisinin biosynthesis. Artemisinin, an endoperoxide sesquiterpene lactone, is a widely used antimalarial drug isolated from Artemisia annua L. Isopentenyl pyrophosphate isomerase (AaIPPI1) catalyzes the interconversion of isopentenyl diphosphate and dimethylallyl diphosphate and is the key gene involved in the biosynthesis of artemisinin. However, the AaIPPI1 gene regulation network remains largely unknown. Here, we isolated the AaIPPI1 promoter (AaIPPI1pro) and predicted that it contains cis-elements involved in stress responses, including the TGACG motif (a methyl jasmonate-responsive element), GARE motif (a gibberellin-responsive element), ABRE (an abscisic acid-responsive element), TC-rich repeats (a stress-responsive element), and the AGT-N_1-10-AGT box, which is the binding site of Cys/His2 zinc finger protein (C2H2 ZFP). The C2H2 ZFP gene AaZFP1 was discovered by screening a cDNA library using AaIPPI1pro as bait in yeast. AaZFP1 contains two conserved C2H2 regions, a nuclear localization domain (B box), a Leu-rich domain (L box), and a conserved DLN sequence (DLN box) close to its C terminus. A subcellular localization assay indicated that AaZFP1 protein is localized in the nucleus and cytoplasm. An electrophoretic mobility shift assay demonstrated that AaZFP1 binds to the AGT-N_1-10-AGT box of AaIPPI1pro. A dual-luciferase assay indicated that AaZFP1 enhanced the promoter activity of AaIPPI1 in vivo. Transient overexpression of AaZFP1 in A. annua increased the expression of AaIPPI1 and the content of artemisinin. Our data demonstrated that AaZFP1 functions as a transcriptional activator that regulates the expression of AaIPPI1 by directly binding to its promoter. The present study provides insights into the transcriptional regulation of genes involved in artemisinin biosynthesis in A. annua.

Elucidating the functional role of heat stress transcription factor A6b (TaHsfA6b) in linking heat stress response and the unfolded protein response in wheat

TaHsfA6b-4D relocalizes intracellularly upon heat stress and play a significant role in linking the heat stress response to unfolded-protein response so as to maintain cellular homeostasis. Heat stress transcription factors (Hsfs) play a crucial role in protecting the plants against heat stress (HS). In case of wheat, TaHsfA6b-4D (earlier known as TaHsfA2d) has been identified as a seed preferential transcription factor and its role has been shown in various abiotic stresses such as heat, salt and drought stress. In the present study, a homeologue of TaHsfA6b gene (TaHsfA6b-4A) was identified and was found to be transcriptionally inactive but it localized to the nucleus. Interestingly, TaHsfA6b-4D localized to the endoplasmic reticulum-Golgi complex and peroxisomes under non-stress conditions, but was observed to accumulate in the nucleus upon HS. The expression of TaHsfA6b-4D was upregulated by dithiothreitol (DTT), which is a known ER stress inducer. Consistent with this, Arabidopsis transgenic plants overexpressing TaHsfA6b-4D performed better on DTT containing media, which further corroborated with the increased expression of ER stress marker genes in these transgenic plants in comparison to the wild type plants. Thus, these studies together suggest that TaHsfA6b-4D may relocalize intracellularly upon heat stress and may play a significant role in linking the unfolded-protein response with heat stress response so as to maintain protein homeostasis inside the cell under heat stress.

Characterization of the Wheat Heat Shock Factor TaHsfA2e-5D Conferring Heat and Drought Tolerance in Arabidopsis

Environmental stresses, especially heat and drought, severely limit plant growth and negatively affect wheat yield and quality worldwide. Heat shock factors (Hsfs) play a central role in regulating plant responses to various stresses. In this study, the wheat heat shock factor gene TaHsfA2e-5D on chromosome 5D was isolated and functionally characterized, with the goal of investigating its role in responses to heat and drought stresses. Gene expression profiling showed that TaHsfA2e-5D was expressed constitutively in various wheat tissues, most highly in roots at the reproductive stage. The expression of TaHsfA2e-5D was highly up-regulated in wheat seedlings by heat, cold, drought, high salinity, and multiple phytohormones. The TaHsfA2e-5D protein was localized in the nucleus and showed a transcriptional activation activity. Ectopic expression of the TaHsfA2e-5D in yeast exhibited improved thermotolerance. Overexpression of the TaHsfA2e-5D in Arabidopsis results in enhanced tolerance to heat and drought stresses. Furthermore, RT-qPCR analyses revealed that TaHsfA2e-5D functions through increasing the expression of Hsp genes and other stress-related genes, including APX2 and GolS1. Collectively, these results suggest that TaHsfA2e-5D functions as a positive regulator of plants’ responses to heat and drought stresses, which may be of great significance for understanding and improving environmental stress tolerance in crops.

Analyzing the regulatory role of heat shock transcription factors in plant heat stress tolerance: a brief appraisal

An increase in ambient temperature throughout the twenty-first century has been described as a "worldwide threat" for crop production. Due to their sessile lifestyles, plants have evolved highly sophisticated and complex heat stress response (HSR) mechanisms to respond to higher temperatures. The HSR allows plants to minimize the damages caused by heat stress (HS), thus enabling cellular protection. HSR is crucial for their lifecycle and yield, particularly for plants grown in the field. At the cellular level, HSR involves the production of heat shock proteins (HSPs) and other stress-responsive proteins to counter the negative effects of HS. The expression of most HSPs is transcriptionally regulated by heat shock transcription factors (HSFs). HSFs are a group of evolutionary conserved regulatory proteins present in all eukaryotes and regulate various stress responses and biological processes in plants. In recent years, significant progress has been made in deciphering the complex regulatory network of HSFs, and several HSFs not only from model plants but also from major crops have been functionally characterized. Therefore, this review explores the progress made in this fascinating research area and debates the further potential to breed thermotolerant crop cultivars through the modulation of HSF networks. Furthermore, we discussed the role of HSFs in plant HS tolerance in a class-specific manner and shed light on their functional diversity, which is evident from their mode of action. Additionally, some research gaps have been highlighted concerning class-specific manners.

Comparative Analysis of HSF Genes From Secale cereale and its Triticeae Relatives Reveal Ancient and Recent Gene Expansions

Plants have evolved sophisticated systems to cope with the environmental stresses, with the heat shock factor (HSF) family proteins composing an integral part of the transcriptional regulation system. Understanding the evolutionary history and functional diversity of HSFs will facilitate improving tolerance of crops to adverse environmental conditions. In this study, genome-wide analysis of Secale cereale identified 31 HSF genes. The total number of HSF genes in S. cereale is larger than that in barley and the three subgenomes of wheat, suggesting it is a valuable resource for mining functional HSFs. Chromosome analysis revealed an uneven distribution of HSF genes among the 7 S. cereale chromosomes, with no HSF gene was detected on chromosome 4. Further interspecies synteny analysis revealed that chromosome reorganization during species-speciation may lead to the escape of HSF genes from the S. cereale chromosome 4. Phylogenetic analysis revealed that S. cereale experienced more HSF gene duplications than barley and the three wheat subgenomes. Expression analysis demonstrated that S. cereale HSF genes showed diverse expression patterns across plant developmental stages and upon drought and freezing treatment, suggesting functional diversity of the gene family. Notably, we detected distinct expression patterns for a recently duplicated HSF gene pair, indicating functional divergence may have occurred between the two genes. The study presents the genome organization, evolutionary features and expression patterns of the S. cereale HSF genes. These results provide new insights into the evolution of HSF genes in Triticeae and may serve as a resource for Triticeae molecular breeding.

A Novel Heat Shock Transcription Factor (ZmHsf08) Negatively Regulates Salt and Drought Stress Responses in Maize

Heat shock transcription factors (HSFs) play important roles in plant growth, development, and stress responses. However, the function of these transcription factors in abiotic stress responses in maize (Zea mays) remains largely unknown. In this study, we characterized a novel HSF transcription factor gene, ZmHsf08, from maize. ZmHsf08 was highly homologous to SbHsfB1, BdHsfB1, and OsHsfB1, and has no transcriptional activation activity. The expression profiles demonstrated that ZmHsf08 was differentially expressed in various organs of maize and was induced by salt, drought, and abscisic acid (ABA) treatment. Moreover, the overexpression of ZmHsf08 in maize resulted in enhanced sensitivity to salt and drought stresses, displaying lower survival rates, higher reactive oxygen species (ROS) levels, and increased malondialdehyde (MDA) contents compared with wild-type (WT) plants. Furthermore, RT-qPCR analyses revealed that ZmHsf08 negatively regulates a number of stress/ABA-responsive genes under salt and drought stress conditions. Collectively, these results indicate that ZmHsf08 plays a negative role in response to salt and drought stresses in maize.

High light and temperature reduce photosynthetic efficiency through different mechanisms in the C4 model Setaria viridis

C₄ plants frequently experience high light and high temperature conditions in the field, which reduce growth and yield. However, the mechanisms underlying these stress responses in C₄ plants have been under-explored, especially the coordination between mesophyll (M) and bundle sheath (BS) cells. We investigated how the C₄ model plant Setaria viridis responded to a four-hour high light or high temperature treatment at photosynthetic, transcriptomic, and ultrastructural levels. Although we observed a comparable reduction of photosynthetic efficiency in high light or high temperature treated leaves, detailed analysis of multi-level responses revealed important differences in key pathways and M/BS specificity responding to high light and high temperature. We provide a systematic analysis of high light and high temperature responses in S. viridis, reveal different acclimation strategies to these two stresses in C₄ plants, discover unique light/temperature responses in C₄ plants in comparison to C₃ plants, and identify potential targets to improve abiotic stress tolerance in C₄ crops.

Genomic Analysis of Soybean PP2A-B ' ' Family and Its Effects on Drought and Salt Tolerance

Abiotic stresses induce the accumulation of reactive oxygen species (ROS) and significantly affect plant growth. Protein phosphatase 2A (PP2A) plays an important role in controlling intracellular and extracellular ROS signals. However, the interaction between PP2A, ROS, and stress tolerance remains largely unclear. In this study, we found that the B ' ' subunit of PP2A (PP2A-B ' ' ) can be significantly induced and was analyzed using drought- and salt-induced soybean transcriptome data. Eighty-three soybean PP2A-B ' ' genes were identified from the soybean genome via homologous sequence alignment, which was distributed across 20 soybean chromosomes. Among soybean PP2A-B ' ' family genes, 26 GmPP2A-B ' ' members were found to be responsive to drought and salt stresses in soybean transcriptome data. Quantitative PCR (qPCR) analysis demonstrated that GmPP2A-B ' ' 71 had the highest expression levels under salt and drought stresses. Functional analysis demonstrated that overexpression of GmPP2A-B ' ' 71 in soybeans can improve plant tolerance to drought and salt stresses; however, the interference of GmPP2A-B ' ' 71 in soybean increased the sensibility to drought and salt stresses. Further analysis demonstrated that overexpression of GmPP2A-B ' ' 71 in soybean could enhance the expression levels of stress-responsive genes, particularly genes associated with ROS elimination. These results indicate that PP2A-B ' ' can promote plant stress tolerance by regulating the ROS signaling, which will contribute to improving the drought resistance of crops.