A genetic module at one locus in rice protects chloroplasts to enhance thermotolerance

GSK3s promote the phyB-ELF3-HMR complex formation to regulate plant thermomorphogenesis

Although elevated ambient temperature causes many effects on plant growth and development, the mechanisms of plant high-ambient temperature sensing remain unknown. In this study, we show that GLYCOGEN SYNTHASE KINASE 3s (GSK3s) negatively regulate high-ambient temperature response and oligomerize upon high-temperature treatment. We demonstrate that GSK3 kinase BIN2 specifically interacts with the high-temperature sensor phytochrome B (phyB) but not the high-temperature sensor EARLY FLOWER 3 (ELF3) to phosphorylate and promote phyB photobody formation. Furthermore, we show that phosphorylation of phyB by GSK3s promotes its interaction with ELF3. Subsequently, we find that ELF3 recruits the phyB photobody facilitator HEMERA (HMR) to promote its association with phyB. Taken together, our data reveal a mechanism that GSK3s promote the phyB-ELF3-HMR complex formation in regulating plant thermomorphogenesis.

OsIAA7 enhances heat stress tolerance by inhibiting the activity of OsARF6 in rice

Heat stress (HS) severely affects the growth and yield of rice, necessitating a clear understanding of the molecular mechanisms underlying HS tolerance. In this study, we report that the Aux/IAA family gene, OsIAA7, whose expression is induced by HS and positively regulates HS tolerance in rice (Oryza sativa L.). The osiaa7 mutant exhibits reduced HS tolerance, whereas overexpression of OsIAA7 enhances it. Our findings suggest that OsIAA7 contributes to HS tolerance by reducing hydrogen peroxide accumulation and cell death. Physiological analysis indicates that OsIAA7 influences the levels of malondialdehyde, catalase, and chlorophyll A concentration in plants under HS conditions. RNA-seq analysis suggests that OsIAA7 modulates the expression of heat-responsive genes, contributing to HS tolerance. Further, biochemical analyses demonstrate a physical interaction between OsIAA7 and OsARF6, with OsIAA7 inhibiting the activity of OsARF6. RT-qPCR results support the notion that the positive regulatory factor OsIAA7 and the negative regulatory factor OsARF6 control HS tolerance by regulating the transcript levels of OsTT1 and OsTT3.1. Together, our results reveal the role of OsIAA7 in controlling HS tolerance through the modulation of physiological processes and the inhibition of OsARF6 activity, suggesting that some Aux/IAA family genes play a role in heat tolerance in rice.

A molecular module improves rice grain quality and yield at high temperatures

Excessive temperatures during grain filling can compromise endosperm starch biosynthesis and decrease grain quality and yield in rice. However, the molecular mechanisms underlying these remain unclear. Here, we show that heat shock protein OsHsp40-1 interacts with and elevates the ATPase activity of OsHsp70-2 in rice. OsHsp40-1 also interacts with the key starch biosynthetic enzymes OsGBSSI and OsPPDKB and thereby enhances their stability and activity, which is essential for maintaining rice quality and grain yield under moderate high-temperature (HT) conditions. Overexpression of OsHsp70-2 and OsHsp40-1 in rice significantly improved grain quality and yield at HT. Furthermore, a haplotype analysis identified favorable alleles of OsHsp70-2 and OsHsp40-1, which could be used for improving thermotolerance in rice. Collectively, our findings reveal a novel mechanism by which the OsHsp70-2-OsHsp40-1 module ameliorates the effects of HT on starch biosynthesis, providing a new strategy for genetic improvement of rice quality and yield under HT conditions.

Engineering source-sink relations by prime editing confers heat-stress resilience in tomato and rice

A 2°C climate-warming scenario is expected to further exacerbate average crop losses by 3%-13%, yet few heat-tolerant staple-crop varieties are available toward meeting future food demands. Here, we develop high-efficiency prime-editing tools to precisely knockin a 10-bp heat-shock element (HSE) into promoters of cell-wall-invertase genes (CWINs) in elite rice and tomato cultivars. HSE insertion endows CWINs with heat-responsive upregulation in both controlled and field environments to enhance carbon partitioning to grain and fruits, resulting in per-plot yield increases of 25% in rice cultivar Zhonghua11 and 33% in tomato cultivar Ailsa Craig over heat-stressed controls, without fruit quality penalties. Up to 41% of heat-induced grain losses were rescued in rice. Beyond a prime-editing system for tweaking gene expression by efficiently delivering bespoke changes into crop genomes, we demonstrate broad and robust utility for targeted knockin of cis-regulatory elements to optimize source-sink relations and boost crop climate resilience.

The NAT1-bHLH110-CER1/CER1L module regulates heat stress tolerance in rice

Rice production is facing substantial threats from global warming associated with extreme temperatures. Here we report that modifying a heat stress-induced negative regulator, a negative regulator of thermotolerance 1 (NAT1), increases wax deposition and enhances thermotolerance in rice. We demonstrated that the C2H2 family transcription factor NAT1 directly inhibits bHLH110 expression, and bHLH110 directly promotes the expression of wax biosynthetic genes CER1/CER1L under heat stress conditions. In situ hybridization revealed that both NAT1 and bHLH110 are predominantly expressed in epidermal layers. By using gene-editing technology, we successfully mutated NAT1 to eliminate its inhibitory effects on wax biosynthesis and improved thermotolerance without yield penalty under normal temperature conditions. Field trials further confirmed the potential of NAT1-edited rice to increase seed-setting rate and grain yield. Therefore, our findings shed light on the regulatory mechanisms governing wax biosynthesis under heat stress conditions in rice and provide a strategy to enhance heat resilience through the modification of NAT1.

Reversing anther thermotolerance by manipulating the cis-elements in the promoter of a high-temperature upregulated gene Casein Kinase I in upland cotton

High temperature (HT) stress causes male sterility, leading to reduced upland cotton yield. Previously, we identified a key gene, Casein Kinase I (GhCKI), that negatively regulates male fertility in upland cotton under HT. However, conventional genetic manipulations of GhCKI would result in male sterility, hindering its utilization in breeding programs. Here, we engineered quantitative variation for anther thermotolerance-related traits in upland cotton by creating weak promoter alleles of GhCKI genes, using CRISPR/Cas9 and CRISPR/Cpf1 genome editing. Then, we screened and identified two new upland cotton plant lines exhibiting a HT-tolerant phenotype with edited GhCKI promoters, and characterized their corresponding heat-tolerant allelic genotypes. Further research revealed that the primary reason for the HT tolerance of the GhCKI promoter editing mutants is that the trans-acting factors GhMYB73 and GhMYB4, which positively regulate GhCKI expression under HT, failed to bind and activate the expression of GhCKI. Overall, our study not only provides a rapid strategy to generate new beneficial alleles but also offers novel germplasm resources and molecular insights for crop HT tolerance breeding.

Morphological, Physiological, and Molecular Responses to Heat Stress in Brassicaceae

Food security is threatened by global warming, which also affects agricultural output. Various components of cells perceive elevated temperatures. Different signaling pathways in plants distinguish between the two types of temperature increases, mild warm temperatures and extremely hot temperatures. Given the rising global temperatures, heat stress has become a major abiotic challenge, affecting the growth and development of various crops and significantly reducing productivity. Brassica napus, the second-largest source of vegetable oil worldwide, faces drastic reductions in seed yield and quality under heat stress. This review summarizes recent research on the genetic and physiological impact of heat stress in the Brassicaceae family, as well as in model plants Arabidopsis and rice. Several studies show that extreme temperature fluctuations during crucial growth stages negatively affect plants, leading to impaired growth and reduced seed production. The review discusses the mechanisms of heat stress adaptation and the key regulatory genes involved. It also explores the emerging understanding of epigenetic modifications during heat stress. While such studies are limited in B. napus, contrasting trends in gene expression have been observed across different species and cultivars, suggesting these genes play a complex role in heat stress tolerance. Key knowledge gaps are identified regarding the impact of heat stress during the growth stages of B. napus. In-depth studies of these stages are still needed. The profound understanding of heat stress response mechanisms in tissue-specific models are crucial in advancing our knowledge of thermo-tolerance regulation in B. napus and supporting future breeding efforts for heat-tolerant crops.

HTT1, a Stearoyl-Acyl Carrier Protein Desaturase Involved Unsaturated Fatty Acid Biosynthesis, Affects Rice Heat Tolerance

Elucidating the mechanisms underlying heat tolerance in rice (Oryza Sativa. L) is vital for adapting this crop to rising global temperature while increasing yields. Here, we identified a rice mutant, high temperature tolerance 1 (htt1), with high survival rates under heat stress. HTT1 encodes a chloroplast-localized stearoyl-acyl carrier protein (ACP) desaturase involved in the biosynthesis of unsaturated fatty acids, converting C18:0 to C18:1 fatty acid. Overexpression and knockout rice lines provided evidence that HTT1 negatively regulates the response to heat stress. In the htt1 mutant, a G-to-A base substitution in HTT1 impairs unsaturated fatty acid biosynthesis, remodelling the lipid content of cellular membranes and in particular increasing diglyceride contents, which improves membrane stability under heat stress. HTT1 was differentially expressed in all tissues analyzed and was inhibited by heat. Yeast one-hybrid and dual-luciferase reporter assays showed that OsHsfA2d binds to the promoter of HTT1, inhibiting its expression. Different HTT1 alleles were identified between the two Asian cultivated rice subspecies, indica and japonica, potentially facilitating their adaptation to different environmental temperature. Taken together, these findings demonstrate that HTT1 is a previously unidentified negative regulator of heat tolerance and a potential target gene for the improvement of heat adaptability in rice.

ZmHSFA2B self-regulatory loop is critical for heat tolerance in maize

The growth and development of maize (Zea mays L.) are significantly impeded by prolonged exposure to high temperatures. Heat stress transcription factors (HSFs) play crucial roles in enabling plants to detect and respond to elevated temperatures. However, the genetic mechanisms underlying the responses of HSFs to heat stress in maize remain unclear. Thus, we aimed to investigate the role of ZmHSFA2B in regulating heat tolerance in maize. Here, we report that ZmHSFA2B has two splicing variants, ZmHSFA2B-I and ZmHSFA2B-II. ZmHSFA2B-I encodes full-length ZmHSFA2B (ZmHSFA2B-I), whereas ZmHSFA2B-II encodes a truncated ZmHSFA2B (ZmHSFA2B-II). Overexpression of ZmHSFA2B-I improved heat tolerance in maize and Arabidopsis thaliana, but it also resulted in growth retardation as a side effect. RNA-sequencing and CUT&Tag analyses identified ZmMBR1 as a putative target of ZmHSFA2B-I. Overexpression of ZmMBR1 also enhanced heat tolerance in Arabidopsis. ZmHSFA2B-II was primarily synthesized in response to heat stress and competitively interacted with ZmHSFA2B-I. This interaction consequently reduced the DNA-binding activities of ZmHSFA2B-I homodimers to the promoter of ZmMBR1. Subsequent investigations indicate that ZmHSFA2B-II limits the transactivation and tempers the function of ZmHSFA2B-I, thereby reducing the adverse effects of excessive ZmHSFA2B-I accumulation. Based on these observations, we propose that the alternative splicing of ZmHSFA2B generates a self-regulatory loop that fine-tunes heat stress response in maize.

Adverse effects of heat shock in rice (Oryza sativa L.) and approaches to mitigate it for sustainable rice production under the changing climate: A comprehensive review

Heat shock, a transient exposure to high temperatures, is a substantial hazard to rice (Oryza sativa L.) production and sustainability. The objective of this review paper is to summarize the impact of heat shock on rice and explore approaches to mitigate its adverse effects to achieve sustainable production. Rice is a staple food for billions of people globally and is extremely sensitive to heat shock. Higher temperatures disturb various physiological and biochemical processes, resulting in decreased growth, development, and ultimately lower grain yield. Heat shock negatively affects important agronomic traits, such as panicle differentiation, pollen viability, fertilization, grain filling, and, ultimately, grain quality. To manage heat shock and sustain rice production, several strategies have been explored, such as modifications to sowing schedules, the substitution of heat-tolerant cultivars for sensitive genotypes, and the use of growth regulators. To improve rice under heat shock, various approaches could be taken: (1) cultivating cultivars that flower early in the morning by adjusting sowing/planting times, modified irrigation, and fertilization; (2) inducing acclimation via growth regulators and organic stimulants and chemicals; (3) breeding genetically resistant cultivars through the integration of appropriate genes; and (4) genetic modification techniques for heat-shock tolerance. Overall, effectively managing heat-shock stress in rice requires a comprehensive strategy that includes developing and using heat shock-tolerant cultivars, adopting suitable cultural practices, utilizing external substances, and applying biotechnological tools. Implementing these strategies collectively will help achieve sustainable rice production in the face of increasing heat-shock conditions.

A genome-wide-level insight into the HSF gene family of Rhodomyrtus tomentosa and the functional divergence of RtHSFA2a and RtHSFA2b in thermal adaptation

Heat shock transcription factor (HSF) is one of the most important regulatory elements in plant development and stress response. Rhohomyrtus tomentosa has many advantages in adapting to high temperature and high humidity climates, whereas its inherence has barely been elucidated. In this study, we aimed to characterize the HSF family and investigate the thermal adaptation mechanisms of R. tomentosa. We identified 25 HSF genes in the R. tomentosa genome. They could be classified into three classes: HSFA, HSFB, and HSFC. Gene duplication events are major motivations for the expansion of the RtHSF gene family. Most of the genes in the same subclass share similar conserved motifs and gene structures. The cis-acting elements of the promoter regions of RtHSF genes are related to development, phytohormone signaling, and stress responses, and they vary among the genes even in the same subclass, resulting in different expression patterns. Especially, there exists subfunctionalization in the RtHSFA2 subfamily in responding to various abiotic stresses, viz. RtHSFA2a is sensitive to drought, salt, and cold stresses, whilst RtHSFA2b is mainly induced by heat stress. We further proved that RtHSFA2b might be of more importance in R. tomentosa thermotolerance, for Arabidopsis plants with overexpressed RtHSFA2b outperformed those with RtHSFA2a under heat stress, and RtHSFA2b had much higher transcription activity than RtHSFA2a in regulating certain heat shock response (HSR) genes. RtHSFA2a plays a role in transactivating RtHSFA2b. All these results provide a general prospect of the RtHSF gene family and enclose a basal thermal adaptation mechanism of R. tomentosa.

Deciphering the Vulnerability of Pollen to Heat Stress for Securing Crop Yields in a Warming Climate

Climate change is leading to more frequent and severe extreme temperature events, negatively impacting agricultural productivity and threatening global food security. Plant reproduction, the process fundamental to crop yield, is highly susceptible to heatwaves, which disrupt pollen development and ultimately affect seed-set and crop yields. Recent research has increasingly focused on understanding how pollen grains from various crops react to heat stress at the molecular and cellular levels. This surge in interest over the last decade has been driven by advances in genomic technologies, such as single-cell RNA sequencing, which holds significant potential for revealing the underlying regulatory reprogramming triggered by heat stress throughout the various stages of pollen development. This review focuses on how heat stress affects gene regulatory networks, including the heat stress response, the unfolded protein response, and autophagy, and discusses the impact of these changes on various stages of pollen development. It highlights the potential of pollen selection as a key strategy for improving heat tolerance in crops by leveraging the genetic variability among pollen grains. Additionally, genome-wide association studies and population screenings have shed light on the genetic underpinnings of traits in major crops that respond to high temperatures during male reproductive stages. Gene-editing tools like CRISPR/Cas systems could facilitate precise genetic modifications to boost pollen heat resilience. The information covered in this review is valuable for selecting traits and employing molecular genetic approaches to develop heat-tolerant genotypes.

Stress sensing and response through biomolecular condensates in plants

Plants have developed intricate mechanisms for rapid and efficient stress perception and adaptation in response to environmental stressors. Recent research highlights the emerging role of biomolecular condensates in modulating plant stress perception and response. These condensates function through numerous mechanisms to regulate cellular processes such as transcription, translation, RNA metabolism, and signaling pathways under stress conditions. In this review, we provide an overview of current knowledge on stress-responsive biomolecular condensates in plants, including well-defined condensates such as stress granules, processing bodies, and the nucleolus, as well as more recently discovered plant-specific condensates. By briefly referring to findings from yeast and animal studies, we discuss mechanisms by which plant condensates perceive stress signals and elicit cellular responses. Finally, we provide insights for future investigations on stress-responsive condensates in plants. Understanding how condensates act as stress sensors and regulators will pave the way for potential applications in improving plant resilience through targeted genetic or biotechnological interventions.

A TT1-SCE1 module integrates ubiquitination and SUMOylation to regulate heat tolerance in rice

Heat stress poses a significant threat to grain yield. As an α2 subunit of the 26S proteasome, TT1 has been shown to act as a critical regulator of rice heat tolerance. However, the heat tolerance mechanisms mediated by TT1 remain elusive. In this study, we unveiled that small ubiquitin-like modifier (SUMO)-conjugating enzyme 1 (SCE1), which interacts with TT1 and acts as a downstream component of TT1, is engaged in TT1-mediated 26S proteasome degradation. We showed that SCE1 functions as a negative regulator of heat tolerance in rice, which is associated with its ubiquitination modification. Furthermore, we observed that small heat-shock proteins (sHSPs) such as Hsp24.1 and Hsp40 can undergo SUMOylation mediated by SCE1, leading to increased accumulation of sHSPs in the absence of SCE1. Reducing protein levels of SCE1 significantly enhanced grain yield under high-temperature stress by improving seed-setting rate and rice grain filling capacity. Taken together, these results uncover the critical role of SCE1 in the TT1-mediated heat tolerance pathway by regulating the abundance of sHSPs and SUMOylation, and ultimately modulating rice heat tolerance. These findings underscore the great potential of the TT1-SCE1 module in improving the heat tolerance of crops.

How Rice Responds to Temperature Changes and Defeats Heat Stress

With the intensification of the greenhouse effect, a series of natural phenomena, such as global warming, are gradually recognized; when the ambient temperature increases to the extent that it causes heat stress in plants, agricultural production will inevitably be affected. Therefore, several issues associated with heat stress in crops urgently need to be solved. Rice is one of the momentous food crops for humans, widely planted in tropical and subtropical monsoon regions. It is prone to high temperature stress in summer, leading to a decrease in yield and quality. Understanding how rice can tolerate heat stress through genetic effects is particularly vital. This article reviews how rice respond to rising temperature by integrating the molecular regulatory pathways and introduce its physiological mechanisms of tolerance to heat stress from the perspective of molecular biology. In addition, genome selection and genetic engineering for rice heat tolerance were emphasized to provide a theoretical basis for the sustainability and stability of crop yield-quality structures under high temperatures from the point of view of molecular breeding.

Functions and Mechanisms of Brassinosteroids in Regulating Crop Agronomic Traits

Brassinosteroids (BRs) perform crucial functions controlling plant growth and developmental processes, encompassing many agronomic traits in crops. Studies of BR-related genes involved in agronomic traits have suggested that BRs could serve as a potential target for crop breeding. Given the pleiotropic effect of BRs, a systematic understanding of their functions and molecular mechanisms is conducive for application in crop improvement. Here, we summarize the functions and underlying mechanisms by which BRs regulate the several major crop agronomic traits, including plant architecture, grain size, as well as the specific trait of symbiotic nitrogen fixation in legume crops. For plant architecture, we discuss the roles of BRs in plant height, branching number and leaf erectness, and propose how progress in these fields may contribute to designing crops with optimal agronomic traits and improved grain yield by accurately modifying BR levels and signaling pathways.

COLD6-OSM1 module senses chilling for cold tolerance via 2',3'-cAMP signaling in rice

While it is known that temperature sensors trigger calcium (Ca2+) signaling to confer cold tolerance in cells, less is known about sensors that couple with other secondary messengers. Here, we identify a cold sensor complex of CHILLING-TOLERANCE DIVERGENCE 6 (COLD6) and osmotin-like 1 (OSM1), which triggers 2',3'-cyclic adenosine monophosphate (2',3'-cAMP) production to enhance cold tolerance in rice. COLD6, which is encoded by a major quantitative trait locus (QTL) gene, interacts with the rice G protein α subunit (RGA1) at the plasma membrane under normal conditions. Upon exposure to chilling, cold-induced OSM1 binds to COLD6, kicking out RGA1 from interaction. This triggers an elevation of 2',3'-cAMP levels for enhancing chilling tolerance. Genetic data show that COLD6 negatively regulates cold tolerance and functionally depends on OSM1 in chilling stress. COLD6 alleles were selected during rice domestication. Knockout and natural variation of COLD6 in hybrid rice enhanced chilling tolerance, hinting design potential for breeding. This highlighted a module triggering 2',3'-cAMP to improve chilling tolerance in crops.

The LpHsfA2-molecular module confers thermotolerance via fine tuning of its transcription in perennial ryegrass (Lolium perenne L.)

Temperature sensitivity and tolerance play a key role in plant survival and production. Perennial ryegrass (Lolium perenne L.), widely cultivated in cool-season for forage supply and turfgrass, is extremely susceptible to high temperatures, therefore serving as an excellent grass for dissecting the genomic and genetic basis of high-temperature adaptation. In this study, expression analysis revealed that LpHsfA2, an important gene associated with high-temperature tolerance in perennial ryegrass, is rapidly and substantially induced under heat stress. Additionally, heat-tolerant varieties consistently display elevated expression levels of LpHsfA2 compared with heat-sensitive ones. Comparative haplotype analysis of the LpHsfA2 promoter indicated an uneven distribution of two haplotypes (HsfA2Hap1 and HsfA2Hap2) across varieties with differing heat tolerance. Specifically, the HsfA2Hap1 allele is predominantly present in heat-tolerant varieties, while the HsfA2Hap2 allele exhibits the opposite pattern. Overexpression of LpHsfA2 confers enhanced thermotolerance, whereas silencing of LpHsfA2 compromises heat tolerance. Furthermore, LpHsfA2 orchestrates its protective effects by directly binding to the promoters of LpHSP18.2 and LpAPX1 to activate their expression, preventing the non-specific misfolding of intracellular protein and the accumulation of reactive oxygen species in cells. Additionally, LpHsfA4 and LpHsfA5 were shown to engage directly with the promoter of LpHsfA2, upregulating its expression as well as the expression of LpHSP18.2 and LpAPX1, thus contributing to enhanced heat tolerance. Markedly, LpHsfA2 possesses autoregulatory ability by directly binding to its own promoter to modulate the self-transcription. Based on these findings, we propose a model for modulating the thermotolerance of perennial ryegrass by precisely regulating the expression of LpHsfA2. Collectively, these findings provide a scientific basis for the development of thermotolerant perennial ryegrass cultivars.

A chloroplast localized heavy metal-associated domain containing protein regulates grain calcium accumulation in rice

Calcium (Ca) is an essential mineral nutrient and plays a crucial signaling role in all living organisms. Increasing Ca content in staple foods such as rice is vital for improving Ca nutrition of humans. Here we map a quantitative trait locus that controls Ca concentration in rice grains and identify the causal gene as GCSC1 (Grain Ca and Sr Concentrations 1), which encodes a chloroplast vesicle localized homo-oligomeric protein. GCSC1 exhibits Ca2+ transport activity in heterologous assays in yeast and Xenopus laevis oocytes and is involved in the efflux of Ca2+ from the chloroplast to the cytosol. Knockout of GCSC1 results in increased chloroplast Ca concentration, lower stomatal conductance in leaves and enhanced Ca allocation to grains. Natural variation in grain Ca concentration is attributed to the variable expression of GCSC1 resulting from its promoter sequence variation. Our study identifies a chloroplast localized heavy metal-associated domain containing protein that regulates chloroplast Ca2+ efflux and provides a way to biofortify Ca in rice to benefit human nutrition.

E3 ligase DECREASED GRAIN SIZE 1 promotes degradation of a G-protein subunit and positively regulates grain size in rice

Grain size is one of the most important traits determining crop yield. However, the mechanism controlling grain size remains unclear. Here, we confirmed the E3 ligase activity of DECREASED GRAIN SIZE 1 (DGS1) in positive regulation of grain size in rice (Oryza sativa) suggested in a previous study. Rice G-protein subunit gamma 2 (RGG2), which negatively regulates grain size, was identified as an interacting protein of DGS1. Biochemical analysis suggested that DGS1 specifically interacts with canonical Gγ subunits (rice G-protein subunit gamma 1 [RGG1] and rice G-protein subunit gamma 2 [RGG2]) rather than non-canonical Gγ subunits (DENSE AND ERECT PANICLE 1 [DEP1], rice G-protein gamma subunit type C 2 [GCC2], GRAIN SIZE 3 [GS3]). We also identified the necessary domains for interaction between DGS1 and RGG2. As an E3 ligase, DGS1 ubiquitinated and degraded RGG2 via a proteasome pathway in several experiments. DGS1 also ubiquitinated RGG2 by its K140, K145, and S147 residues. Thus, this work identified a substrate of the E3 ligase DGS1 and elucidated the post-transcriptional regulatory mechanism of the G-protein signaling pathway in the control of grain size.

OsRHS Negatively Regulates Rice Heat Tolerance at the Flowering Stage by Interacting With the HSP Protein cHSP70-4

Heat stress at the flowering stage significantly impacts rice grain yield, yet the number of identified genes associated with rice heat tolerance at this crucial stage remains limited. This study focuses on elucidating the function of the heat-induced gene reduced heat stress tolerance 1 (OsRHS). Overexpression of OsRHS leads to reduced heat tolerance, while RNAi silencing or knockout of OsRHS enhances heat tolerance without compromising yield, as assessed by the seed setting rate. OsRHS is localized in the cytoplasm and mainly expressed in the glume and anther of spikelet. Moreover, OsRHS was found to interact with the HSP protein cHSP70-4, and the knockout of cHSP70-4 resulted in increased heat tolerance. Complementation assays revealed that the knockout of cHSP70-4 could restore the compromised heat tolerance in OsRHS overexpression plants. Additional investigation reveals that elevated temperatures can amplify the bond between OsRHS and cHSP70-4 within rice. Furthermore, our findings indicate that under heat stress conditions during the flowering stage, OsRHS plays a negative regulatory role in the expression of many stress-related genes. These findings unveil the crucial involvement of OsRHS and cHSP70-4 in modulating heat tolerance in rice and identify novel target genes for enhancing heat resilience during the flowering phase in rice.

Protein degrons and degradation: Exploring substrate recognition and pathway selection in plants

Proteome composition is dynamic and influenced by many internal and external cues, including developmental signals, light availability, or environmental stresses. Protein degradation, in synergy with protein biosynthesis, allows cells to respond to various stimuli and adapt by reshaping the proteome. Protein degradation mediates the final and irreversible disassembly of proteins, which is important for protein quality control and to eliminate misfolded or damaged proteins, as well as entire organelles. Consequently, it contributes to cell resilience by buffering against protein or organellar damage caused by stresses. Moreover, protein degradation plays important roles in cell signaling, as well as transcriptional and translational events. The intricate task of recognizing specific proteins for degradation is achieved by specialized systems that are tailored to the substrate's physicochemical properties and subcellular localization. These systems recognize diverse substrate cues collectively referred to as "degrons," which can assume a range of configurations. They are molecular surfaces recognized by E3 ligases of the ubiquitin-proteasome system but can also be considered as general features recognized by other degradation systems, including autophagy or even organellar proteases. Here we provide an overview of the newest developments in the field, delving into the intricate processes of protein recognition and elucidating the pathways through which they are recruited for degradation.

Genomic and transcriptomic analyses of the elite rice variety Huizhan provide insight into disease resistance and heat tolerance

The indica rice variety Huizhan shows elite traits of disease resistance and heat tolerance. However, the underlying genetic basis of these traits is not fully understood due to limited genomic resources. Here, we used Nanopore long-read and next-generation sequencing technologies to generate a chromosome-scale genome assembly of Huizhan. Comparative genomics analysis uncovered a large chromosomal inversion and expanded gene families that are associated with plant growth, development and stress responses. Functional rice blast resistance genes, including Pi2, Pib and Ptr, and bacterial blight resistance gene Xa27, contribute to disease resistance of Huizhan. Furthermore, integrated genomics and transcriptomics analyses showed that OsHIRP1, OsbZIP60, the SOD gene family, and various transcription factors are involved in heat tolerance of Huizhan. The high-quality genome assembly and comparative genomics results presented in this study facilitate the use of Huizhan as an elite parental line in developing rice varieties adapted to disease pressure and climate challenges.

Exploring the interplay between angiosperm chlorophyll metabolism and environmental factors

MAIN CONCLUSION

In this review, we summarize how chlorophyll metabolism in angiosperm is affected by the environmental factors: light, temperature, metal ions, water, oxygen, and altitude. The significance of chlorophyll (Chl) in plant leaf morphogenesis and photosynthesis cannot be overstated. Over time, researchers have made significant advancements in comprehending the biosynthetic pathway of Chl in angiosperms, along with the pivotal enzymes and genes involved in this process, particularly those related to heme synthesis and light-responsive mechanisms. Various environmental factors influence the stability of Chl content in angiosperms by modulating Chl metabolic pathways. Understanding the interplay between plants Chl metabolism and environmental factors has been a prominent research topic. This review mainly focuses on angiosperms, provides an overview of the regulatory mechanisms governing Chl metabolism, and the impact of environmental factors such as light, temperature, metal ions (iron and magnesium), water, oxygen, and altitude on Chl metabolism. Understanding these effects is crucial for comprehending and preserving the homeostasis of Chl metabolism.

A protoplast-based transient gene expression assay for the identification of heat and oxidative stress-regulatory genes in perennial ryegrass

BACKGROUND

With the accumulating omics data, an efficient and time-saving transient assay to express target genes is desired. Mesophyll protoplasts, maintaining most stress-physiological responses and cellular activities as intact plants, offer an alternative transient assay to study target genes' effects on heat and oxidative stress responses.

RESULTS

In this study, a perennial ryegrass (Lolium perenne L.) mesophyll protoplast-based assay was established to effectively over- or down-regulate target genes. The relative expression levels of the target genes could be quantified using RT-qPCR, and the effects of heat and H2O2-induced oxidative stress on protoplasts' viability could be quantitatively measured. The practicality of the assay was demonstrated by identifying the potential thermos-sensor genes LpTT3.1/LpTT3.2 in ryegrass that over-expressing these genes significantly altered protoplasts' viability rates after heat stress.

CONCLUSION

This protoplast-based rapid stress regulatory gene identification assay was briefed as 'PRIDA' that will complement the stable genetic transformation studies to rapidly identify candidate stress-regulatory genes in perennial ryegrass and other grass species.

Cloning and functional verification of the CmHSP17.9 gene from chrysanthemum

Small molecular heat shock proteins (sHSPs) belong to the HSP family of molecular chaperones. Under high-temperature stress, they can prevent the aggregation of irreversible proteins and maintain the folding of denatured proteins to enhance heat resistance. In this study, the CmHSP17.9-1 and CmHSP17.9-2 genes, which were cloned from chrysanthemum (Chrysanthemum×morifolium 'Jinba') by homologous cloning, had a complete open reading frame of 480 bp each, encoding 159 amino acids. The protein subcellular localization analysis showed that CmHSP17.9-1 and CmHSP17.9-2 were located in the cytoplasm and mostly aggregated in granules, especially around the nucleus. Real-time quantitative PCR (qRT-PCR) analysis showed that the relative expression level of the CmHSP17.9-1 and CmHSP17.9-2 genes was highest in the terminal buds of the chrysanthemum, followed by the leaves. CmHSP17.9-1 and CmHSP17.9-2 overex-pression vectors were constructed and used to transform the chrysanthemum; overexpression of these genes led to the chrysanthemum phenotypes being less affected by high-temperature, and the antioxidant capacity was enhanced. The results showed that chrysanthemum with overex-pression of the CmHSP17.9-1 and CmHSP17.9-2 genes had stronger tolerance than the wild type chrysanthemum after high-temperature treatment or some degree of heat exercise, and overex-pression of the CmHSP17.9-1 gene led to stronger heat resistance than that of the CmHSP17.9-2 gene, providing an important theoretical basis for the subsequent molecular breeding and pro-duction applications of chrysanthemum.

FKF1b controls reproductive transition associated with adaptation to geographical distribution in maize

Maize (Zea mays subspecies mays) is an important commercial crop across the world, and its flowering time is closely related to grain yield, plant cycle and latitude adaptation. FKF1 is an essential clock-regulated blue-light receptor with distinct functions on flowering time in plants, and its function in maize remains unclear. In this study, we identified two FKF1 homologs in the maize genome, named ZmFKF1a and ZmFKF1b, and indicated that ZmFKF1a and ZmFKF1b independently regulate reproductive transition through interacting with ZmCONZ1 and ZmGI1 to increase the transcription levels of ZmCONZ1 and ZCN8. We demonstrated that ZmFKF1b underwent artificial selection during modern breeding in China probably due to its role in geographical adaptation. Furthermore, our data suggested that ZmFKF1bHap_C7 may be an elite allele, which increases the abundance of ZmCONZ1 mRNA more efficiently and adapt to a wider range of temperature zone than that of ZmFKF1bHap_Z58 to promote maize floral transition. It extends our understanding of the genetic diversity of maize flowering. This allele is expected to be introduced into tropical maize germplasm to enrich breeding resources and may improve the adaptability of maize at different climate zones, especially at temperate region.

Plant thermosensors

Plants dynamically regulate their genes expression and physiological outputs to adapt to changing temperatures. The underlying molecular mechanisms have been extensively studied in diverse plants and in multiple dimensions. However, the question of exactly how temperature is detected at molecular level to transform the physical information into recognizable intracellular signals remains continues to be one of the undetermined occurrences in plant science. Recent studies have provided the physical and biochemical mechanistic breakthrough of how temperature changes can influence molecular thermodynamically stability, thus changing molecular structures, activities, interaction and signaling transduction. In this review, we focus on the thermosensing mechanisms of recognized and potential plant thermosensors, to describe the multi-level thermal input system in plants. We also consider the attributes of a thermosensor on the basis of thermal-triggered changes in function, structure, and physical parameters. This study thus provides a reference for discovering more plant thermosensors and elucidating plant thermal adaptive mechanisms.

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.

Phylogenomic profiles of whole-genome duplications in Poaceae and landscape of differential duplicate retention and losses among major Poaceae lineages

Poaceae members shared a whole-genome duplication called rho. However, little is known about the evolutionary pattern of the rho-derived duplicates among Poaceae lineages and implications in adaptive evolution. Here we present phylogenomic/phylotranscriptomic analyses of 363 grasses covering all 12 subfamilies and report nine previously unknown whole-genome duplications. Furthermore, duplications from a single whole-genome duplication were mapped to multiple nodes on the species phylogeny; a whole-genome duplication was likely shared by woody bamboos with possible gene flow from herbaceous bamboos; and recent paralogues of a tetraploid Oryza are implicated in tolerance of seawater submergence. Moreover, rho duplicates showing differential retention among subfamilies include those with functions in environmental adaptations or morphogenesis, including ACOT for aquatic environments (Oryzoideae), CK2β for cold responses (Pooideae), SPIRAL1 for rapid cell elongation (Bambusoideae), and PAI1 for drought/cold responses (Panicoideae). This study presents a Poaceae whole-genome duplication profile with evidence for multiple evolutionary mechanisms that contribute to gene retention and losses.

Crop bioengineering via gene editing: reshaping the future of agriculture

Genome-editing technologies have revolutionized research in plant biology, with major implications for agriculture and worldwide food security, particularly in the face of challenges such as climate change and increasing human populations. Among these technologies, clustered regularly interspaced short palindromic repeats [CRISPR]-CRISPR-associated protein [Cas] systems are now widely used for editing crop plant genomes. In this review, we provide an overview of CRISPR-Cas technology and its most significant applications for improving crop sustainability. We also review current and potential technological advances that will aid in the future breeding of crops to enhance food security worldwide. Finally, we discuss the obstacles and challenges that must be overcome to realize the maximum potential of genome-editing technologies for future crop and food production.

Reactive oxygen species: Multidimensional regulators of plant adaptation to abiotic stress and development

Reactive oxygen species (ROS) are produced as undesirable by-products of metabolism in various cellular compartments, especially in response to unfavorable environmental conditions, throughout the life cycle of plants. Stress-induced ROS production disrupts normal cellular function and leads to oxidative damage. To cope with excessive ROS, plants are equipped with a sophisticated antioxidative defense system consisting of enzymatic and non-enzymatic components that scavenge ROS or inhibit their harmful effects on biomolecules. Nonetheless, when maintained at relatively low levels, ROS act as signaling molecules that regulate plant growth, development, and adaptation to adverse conditions. Here, we provide an overview of current approaches for detecting ROS. We also discuss recent advances in understanding ROS signaling, ROS metabolism, and the roles of ROS in plant growth and responses to various abiotic stresses.

Complex plant responses to drought and heat stress under climate change

Global climate change is predicted to result in increased yield losses of agricultural crops caused by environmental conditions. In particular, heat and drought stress are major factors that negatively affect plant development and reproduction, and previous studies have revealed how these stresses induce plant responses at physiological and molecular levels. Here, we provide a comprehensive overview of current knowledge concerning how drought, heat, and combinations of these stress conditions affect the status of plants, including crops, by affecting factors such as stomatal conductance, photosynthetic activity, cellular oxidative conditions, metabolomic profiles, and molecular signaling mechanisms. We further discuss stress-responsive regulatory factors such as transcription factors and signaling factors, which play critical roles in adaptation to both drought and heat stress conditions and potentially function as 'hubs' in drought and/or heat stress responses. Additionally, we present recent findings based on forward genetic approaches that reveal natural variations in agricultural crops that play critical roles in agricultural traits under drought and/or heat conditions. Finally, we provide an overview of the application of decades of study results to actual agricultural fields as a strategy to increase drought and/or heat stress tolerance. This review summarizes our current understanding of plant responses to drought, heat, and combinations of these stress conditions.

DGS1 improves rice disease resistance by elevating pathogen-associated molecular pattern-triggered immunity

Rice yield and disease resistance are two crucial factors in determining the suitability of a gene for agricultural breeding. Decreased grain size1 (DGS1), encoding an RING-type E3 ligase, has been found to have a positive effect on rice yield by regulating rice grain number and 1000-grain weight. However, the role of DGS1 in rice blast resistance is still unknown. In this study, we report that DGS1 enhances disease resistance by improving PTI responses, including stronger ROS burst and MAPK activation, and also increased expression of defense-related genes. Furthermore, DGS1 works in conjunction with ubiquitin conjugating enzyme OsUBC45 as an E2-E3 pair to facilitate the ubiquitin-dependent degradation of OsGSK3 and OsPIP2;1, thereby influencing rice yield and immunity, respectively. Therefore, the DGS1-OsUBC45 module has the potential in facilitating rice agricultural breeding.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42994-024-00137-9.

ER-associated ubiquitin-conjugating enzyme: a key regulator of grain yield and stress resistance in crops

Recent research reveals the critical roles of endoplasmic reticulum (ER)-associated protein degradation (ERAD)-related ubiquitin-conjugating enzyme AtUBC32 orthologs and their partnering E3 ligases, which play dual roles in enhancing both crop yield and stress resistance. These findings open avenues for breeding high-yield, stress-tolerant crops and inspire further exploration of the ERAD pathway in agricultural innovation.

Systematic identification and characterization of microRNAs with target genes involved in high night temperature stress at the filling stage of rice

High night temperature stress is one of the main environmental factors affecting rice yield and quality. More and more evidence shows that microRNA (miRNA) plays an important role in various abiotic stresses. However, the molecular network of miRNA regulation on rice tolerance to high night temperatures remains unclear. Here, small RNA, transcriptome and degradome sequencing were integrated to identify differentially expressed miRNAs, genes, and key miRNA-target gene pairs in rice heat-sensitive and heat-tolerant lines at the filling stage suffering from high night temperature stress. It was discovered that there were notable differences in the relative expression of 102 miRNAs between the two rice lines under stress. Meanwhile, 5263 and 5405 mRNAs were differentially expressed in the heat-sensitive line and heat-tolerant line, and functional enrichment analysis revealed that these genes were involved in heat-related processes and pathways. The miRNAs-mRNAs target relationship was further verified by degradome sequencing. Eventually, 49 miRNAs-222 mRNAs target pairs with reverse expression patterns showed significant relative expression changes between the heat-tolerant and the heat-sensitive line, being suggested to be responsible for the heat tolerance difference of these two rice lines. Functional analysis of these 222 mRNA transcripts showed that high night temperature-responsive miRNAs targeted these mRNAs involved in many heat-related biological processes, such as transcription regulation, chloroplast regulation, mitochondrion regulation, protein folding, hormone regulation and redox process. This study identified possible miRNA-mRNA regulation relationships in response to high night temperature stress in rice and potentially contributed to heat resistance breeding of rice in the future.

Diurnal regulation of alternative splicing associated with thermotolerance in rice by two glycine-rich RNA-binding proteins

Rice (Oryza sativa L.) production is threatened by global warming associated with extreme high temperatures, and rice heat sensitivity is differed when stress occurs between daytime and nighttime. However, the underlying molecular mechanism are largely unknown. We show here that two glycine-rich RNA binding proteins, OsGRP3 and OsGRP162, are required for thermotolerance in rice, especially at nighttime. The rhythmic expression of OsGRP3/OsGRP162 peaks at midnight, and at these coincident times, is increased by heat stress. This is largely dependent on the evening complex component OsELF3-2. We next found that the double mutant of OsGRP3/OsGRP162 is strikingly more sensitive to heat stress in terms of survival rate and seed setting rate when comparing to the wild-type plants. Interestingly, the defect in thermotolerance is more evident when heat stress occurred in nighttime than that in daytime. Upon heat stress, the double mutant of OsGRP3/OsGRP162 displays globally reduced expression of heat-stress responsive genes, and increases of mRNA alternative splicing dominated by exon-skipping. This study thus reveals the important role of OsGRP3/OsGRP162 in thermotolerance in rice, and unravels the mechanism on how OsGRP3/OsGRP162 regulate thermotolerance in a diurnal manner.

Leveraging brassinosteroids towards the next Green Revolution

The use of gibberellin-related dwarfing genes significantly increased grain yield during the Green Revolution. Brassinosteroids (BRs) play a vital role in regulating agronomic traits and stress resistance. The potential of BR-related genes in crop improvement has been well demonstrated, positioning BRs as crucial targets for the next agricultural biotechnological revolution. However, BRs exert pleiotropic effects on plants, and thus present both opportunities and challenges for their application. Recent research suggests promising strategies for leveraging BR regulatory molecules for crop improvement, such as exploring function-specific genes, identifying beneficial alleles, inducing favorable mutations, and optimizing spatial hormone distribution. Advancing our understanding of the roles of BRs in plants is imperative to implement these strategies effectively.

Plant Adaptation and Tolerance to Heat Stress: Advance Approaches and Future Aspects

Heat stress impacts plant growth at all phases of development, although the particular threshold for heat tolerance varies significantly across different developmental stages. During seed germination, elevated temperatures can either impede or completely halt the process, contingent upon the plant type and the severity of the stress. During advanced stages, high temperatures can have a negative impact on photosynthesis, respiration, water balance, and membrane integrity. Additionally, they can also influence the levels of hormones and primary and secondary metabolites. In addition, during the growth and development of plants, there is an increased expression of various heat shock proteins, as well as other proteins related to stress, and the generation of reactive oxygen species (ROS). These are significant plant responses to heat stress. Plants employ several strategies to deal with heat stress, such as maintaining the stability of their cell membranes, removing harmful reactive oxygen species (ROS), producing antioxidants, accumulating and adjusting compatible solutes, activating mitogen-activated protein kinase (MAPK) and calcium-dependent protein kinase (CDPK) cascades, and, crucially, signaling through chaperones and activating transcription. These molecular-level systems boost the ability of plants to flourish in heat stress. Potential genetic methods to enhance plant heat stress resistance encompass old and modern molecular breeding techniques and transgenic approaches, all of which rely on a comprehensive comprehension of these systems. Although several plants exhibit enhanced heat tolerance through traditional breeding methods, the effectiveness of genetic transformation techniques has been somewhat restricted. The latter results from the current constraints in our understanding and access to genes that have known impacts on plant heat stress tolerance. However, these challenges may be overcome in the future. Besides genetic methods, crops' heat tolerance can be improved through the pre-treatment of plants with various environmental challenges or the external application of osmoprotectants such as glycine betaine and proline. Thermotolerance is achieved through an active process in which plants allocate significant energy to maintain their structure and function to avoid damage induced by heat stress. The practice of nanoparticles has been shown to upgrade both the standard and the quantity of produce when crops are under heat stress. This review provides information on the effects of heat stress on plants and explores the importance of nanoparticles, transgenics, and genomic techniques in reducing the negative consequences of heat stress. Furthermore, it explores how plants might adapt to heat stress by modifying their biochemical, physiological, and molecular reactions.

Plant-derived extracellular vesicles -a novel clinical anti-inflammatory drug carrier worthy of investigation

Plant-derived extracellular vesicles (PDEVs) have shown remarkable potential as sustainable, green, and efficient drug delivery nanocarriers. As natural nanoparticles containing lipids, protein, nucleic acids and secondary metabolites, they have received widespread attention as a replacement for mammalian exosomes in recent years. In this review, the advances in isolation, identification, composition, therapeutic effect, and clinical application prospect were comprehensively reviewed, respectively. In addition, the specific modification strategies have been listed focusing on the inherent drawbacks of the raw PDEVs like low targeting efficiency and poor homogeneity. With emphasis on their biology mechanism in terms of immune regulation, regulating oxidative stress and promoting regeneration in the anti-inflammatory field and application value demonstrated by citing some typical examples, this review about PDEVs would provide a broad and fundamental vision for the in-depth exploration and development of plant-derived extracellular vesicles in the in-vivo anti-inflammation and even other biomedical applications.

The impact of heat stress in plant reproduction

The increment in global temperature reduces crop productivity, which in turn threatens food security. Currently, most of our food supply is produced by plants and the human population is estimated to reach 9 billion by 2050. Gaining insights into how plants navigate heat stress in their reproductive phase is essential for effectively overseeing the future of agricultural productivity. The reproductive success of numerous plant species can be jeopardized by just one exceptionally hot day. While the effects of heat stress on seedlings germination and root development have been extensively investigated, studies on reproduction are limited. The intricate processes of gamete development and fertilization unfold within a brief timeframe, largely concealed within the flower. Nonetheless, heat stress is known to have important effects on reproduction. Considering that heat stress typically affects both male and female reproductive structures concurrently, it remains crucial to identify cultivars with thermotolerance. In such cultivars, ovules and pollen can successfully undergo development despite the challenges posed by heat stress, enabling the completion of the fertilization process and resulting in a robust seed yield. Hereby, we review the current understanding of the molecular mechanisms underlying plant resistance to abiotic heat stress, focusing on the reproductive process in the model systems of Arabidopsis and Oryza sativa.

The Dsup coordinates grain development and abiotic stress in rice

DNA damage is a serious threat to all living organisms and may be induced by environmental stressors. Previous studies have revealed that the tardigrade (Ramazzotius varieornatus) DNA damage suppressor protein Dsup has protective effects in human cells and tobacco. However, whether Dsup provides radiation damage protection more widely in crops is unclear. To explore the effects of Dsup in other crops, stable Dsup overexpression lines through Agrobacterium-mediated transformation were generated and their agronomic traits were deeply investigated. In this study, the overexpression of Dsup not only enhanced the DNA damage resistance at the seeds and seedlings stages, they also exhibited grain size enlargement and starch granule structure and cell size alteration by the scanning electron microscopy observation. Notably, the RNA-seq revealed that the Dsup plants increased radiation-related and abiotic stress-related gene expression in comparison to wild types, suggesting that Dsup is capable to coordinate normal growth and abiotic stress resistance in rice. Immunoprecipitation enrichment with liquid chromatography-tandem mass spectrometry (IP-LC-MS) assays uncovered 21 proteins preferably interacting with Dsup in plants, suggesting that Dsup binds to transcription and translation related proteins to regulate the homeostasis between DNA protection and plant development. In conclusion, our data provide a detailed agronomic analysis of Dsup plants and potential mechanisms of Dsup function in crops. Our findings provide novel insights for the breeding of crop radiation resistance.

Identification of natural allelic variation in TTL1 controlling thermotolerance and grain size by a rice super pan-genome

Continuously increasing global temperatures present great challenges to food security. Grain size, one of the critical components determining grain yield in rice (Oryza sativa L.), is a prime target for genetic breeding. Thus, there is an immediate need for genetic improvement in rice to maintain grain yield under heat stress. However, quantitative trait loci (QTLs) endowing heat stress tolerance and grain size in rice are extremely rare. Here, we identified a novel negative regulator with pleiotropic effects, Thermo-Tolerance and grain Length 1 (TTL1), from the super pan-genomic and transcriptomic data. Loss-of-function mutations in TTL1 enhanced heat tolerance, and caused an increase in grain size by coordinating cell expansion and proliferation. TTL1 was shown to function as a transcriptional regulator and localized to the nucleus and cell membrane. Furthermore, haplotype analysis showed that hapL and hapS of TTL1 were obviously correlated with variations of thermotolerance and grain size in a core collection of cultivars. Genome evolution analysis of available rice germplasms suggested that TTL1 was selected during domestication of the indica and japonica rice subspecies, but still had much breeding potential for increasing grain length and thermotolerance. These findings provide insights into TTL1 as a novel potential target for the development of high-yield and thermotolerant rice varieties.

PWL1, a G-type lectin receptor-like kinase, positively regulates leaf senescence and heat tolerance but negatively regulates resistance to Xanthomonas oryzae in rice

Plant leaf senescence, caused by multiple internal and environmental factors, has an important impact on agricultural production. The lectin receptor-like kinase (LecRLK) family members participate in plant development and responses to biotic and abiotic stresses, but their roles in regulating leaf senescence remain elusive. Here, we identify and characterize a rice premature withered leaf 1 (pwl1) mutant, which exhibits premature leaf senescence throughout the plant life cycle. The pwl1 mutant displayed withered and whitish leaf tips, decreased chlorophyll content, and accelerated chloroplast degradation. Map-based cloning revealed an amino acid substitution (Gly412Arg) in LOC_Os03g62180 (PWL1) was responsible for the phenotypes of pwl1. The expression of PWL1 was detected in all tissues, but predominantly in tillering and mature leaves. PWL1 encodes a G-type LecRLK with active kinase and autophosphorylation activities. PWL1 is localized to the plasma membrane and can self-associate, mainly mediated by the plasminogen-apple-nematode (PAN) domain. Substitution of the PAN domain significantly diminished the self-interaction of PWL1. Moreover, the pwl1 mutant showed enhanced reactive oxygen species (ROS) accumulation, cell death, and severe DNA fragmentation. RNA sequencing analysis revealed that PWL1 was involved in the regulation of multiple biological processes, like carbon metabolism, ribosome, and peroxisome pathways. Meanwhile, interfering of biological processes induced by the PWL1 mutation also enhanced heat sensitivity and resistance to bacterial blight and bacterial leaf streak with excessive accumulation of ROS and impaired chloroplast development in rice. Natural variation analysis indicated more variations in indica varieties, and the vast majority of japonica varieties harbour the PWL1Hap1 allele. Together, our results suggest that PWL1, a member of LecRLKs, exerts multiple roles in regulating plant growth and development, heat-tolerance, and resistance to bacterial pathogens.

Thermosensing and thermal responses in plants

Thermosensors have been identified in plants in recent years. Understanding how plants sense and respond to rising temperatures is of utmost importance currently in terms of global warming and its actual and potential impact on us. This forum explores the recent understanding of plant thermosensing and thermal responses.

Extra- and intranuclear heat perception and triggering mechanisms in plants

The escalating impact of global warming on crop yield and quality poses a significant threat to future food supplies. Breeding heat-resistant crop varieties holds promise, but necessitates a deeper understanding of the molecular mechanisms underlying plant heat tolerance. Recent studies have shed light on the initial events of heat perception in plants. In this review, we provide a comprehensive summary of the recent progress made in unraveling the mechanisms of heat perception and response in plants. Calcium ion (Ca2+), hydrogen peroxide (H2O2), and nitric oxide (NO) have emerged as key participants in heat perception. Furthermore, we discuss the potential roles of the NAC transcription factor NTL3, thermo-tolerance 3.1 (TT3.1), and Target of temperature 3 (TOT3) as thermosensors associated with the plasma membrane. Additionally, we explore the involvement of cytoplasmic HISTONE DEACETYLASE 9 (HDA9), mRNA encoding the phytochrome-interacting factor 7 (PIF7), and chloroplasts in mediating heat perception. This review also highlights the role of intranuclear transcriptional condensates formed by phytochrome B (phyB), EARLY FLOWERING 3 (ELF3), and guanylate-binding protein (GBP)-like GTPase 3 (GBPL3) in heat perception. Finally, we raise the unresolved questions in the field of heat perception that require further investigation in the future.

The E3 ubiquitin ligase CSIT1 regulates critical sterility-inducing temperature by ribosome-associated quality control to safeguard two-line hybrid breeding in rice

Two-line hybrid breeding can fully utilize heterosis in crops. In thermo-sensitive genic male sterile (TGMS) lines, low critical sterility-inducing temperature (CSIT) is vital to safeguard the production of two-line hybrid seeds in rice (Oryza sativa), but the molecular mechanism determining CSIT is unclear. Here, we report the cloning of CSIT1, which encodes an E3 ubiquitin ligase, and show that CSIT1 modulates the CSIT of thermo-sensitive genic male sterility 5 (tms5)-based TGMS lines through ribosome-associated quality control (RQC). Biochemical assays demonstrated that CSIT1 binds to the 80S ribosomes and ubiquitinates abnormal nascent polypeptides for degradation in the RQC process. Loss of CSIT1 function inhibits the possible damage of tms5 to the ubiquitination system and protein translation, resulting in enhanced accumulation of anther-related proteins such as catalase to suppress abnormal accumulation of reactive oxygen species and premature programmed cell death in the tapetum, thereby leading to a much higher CSIT in the tms5-based TGMS lines. Taken together, our findings reveal a regulatory mechanism of CSIT, providing new insights into RQC and potential targets for future two-line hybrid breeding.

Genetic and molecular exploration of maize environmental stress resilience: Toward sustainable agriculture

Global climate change exacerbates the effects of environmental stressors, such as drought, flooding, extreme temperatures, salinity, and alkalinity, on crop growth and grain yield, threatening the sustainability of the food supply. Maize (Zea mays) is one of the most widely cultivated crops and the most abundant grain crop in production worldwide. However, the stability of maize yield is highly dependent on environmental conditions. Recently, great progress has been made in understanding the molecular mechanisms underlying maize responses to environmental stresses and in developing stress-resilient varieties due to advances in high-throughput sequencing technologies, multi-omics analysis platforms, and automated phenotyping facilities. In this review, we summarize recent advances in dissecting the genetic factors and networks that contribute to maize abiotic stress tolerance through diverse strategies. We also discuss future challenges and opportunities for the development of climate-resilient maize varieties.

The molecular basis of heat stress responses in plants

Global warming impacts crop production and threatens food security. Elevated temperatures are sensed by different cell components. Temperature increases are classified as either mild warm temperatures or excessively hot temperatures, which are perceived by distinct signaling pathways in plants. Warm temperatures induce thermomorphogenesis, while high-temperature stress triggers heat acclimation and has destructive effects on plant growth and development. In this review, we systematically summarize the heat-responsive genetic networks in Arabidopsis and crop plants based on recent studies. In addition, we highlight the strategies used to improve grain yield under heat stress from a source-sink perspective. We also discuss the remaining issues regarding the characteristics of thermosensors and the urgency required to explore the basis of acclimation under multifactorial stress combination.

A new family of proteins is required for tethering of Casparian strip membrane domain and nutrient homoeostasis in rice

Cell-cell junctions are essential for multicellular organisms to maintain nutrient homoeostasis. A plant-type tight junction, the Casparian strip (CS)-Casparian strip membrane domain (CSD) that seals the paracellular space between adjacent endodermal cells, has been known for more than one hundred years. However, the molecular basis of this structure remains unknown. Here we report that a new family of proteins containing a glycine/alanine/proline-rich domain, a lectin domain and a secretory signal peptide (GAPLESS) mediates tethering of the plasma membrane to the CS in rice. The GAPLESS proteins are specifically localized in the CS of root endodermal cells, and loss of their functions results in a disabled cell-cell junction and disrupted nutrient homoeostasis. The GAPLESS protein forms a tight complex with OsCASP1 in the plasma membrane, thereby mediating the CS-CSD junction. This study provides valuable insights into the junctional complex of plant endodermal cells, shedding light on our understanding of nutrient homoeostasis in crops and the cell junctions of eukaryotes.