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

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.

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.

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.

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 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.

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.

The Role of Histone Modifications in Heat Signal Transduction in Plants

Global warming and the more frequent occurrence of extremly high temperatures seriously affect crop yields. Heat stress (HS) has become a major environmental factor threatening food security worldwide. Understanding how plants sense and respond to HS is of clear interest to plant scientists and crop breeders. However, it is not trivial to elucidate the underlying signaling cascade, as specific cellular responses (ranging from detrimental to systemic effects) must be disentangled. Plants respond and adapt to high temperatures in many ways. In this review, recent progress in understanding heat signal transduction and the role of histone modifications in regulating the expression of genes involved in HS responses are discussed. The outstanding issues that are crucial for understanding the interactions between plants and HS are also discussed. The study of heat signal transduction mechanisms in plants is essential to facilitate the cultivation of heat-resistant crop varieties.

It is time to move: Heat-induced translocation events

Climate change-induced temperature fluctuations impact agricultural productivity through short-term intense heat waves or long-term heat stress. Plants have evolved sophisticated strategies to deal with heat stress. Understanding perception and transduction of heat signals from outside to inside cells is essential to improve plant thermotolerance. In this review, we will focus on translocation of molecules and proteins associated with signal transduction to understand how plant cells decode signals from the environment to trigger a suitable response.

Transcriptome Analysis Reveals the Dynamic and Rapid Transcriptional Reprogramming Involved in Heat Stress and Identification of Heat Response Genes in Rice

High temperature is one of the most important environmental factors influencing rice growth, development, and yield. Therefore, it is important to understand how rice plants cope with high temperatures. Herein, the heat tolerances of T2 (Jinxibai) and T21 (Taizhongxianxuan2hao) were evaluated at 45 °C, and T21 was found to be sensitive to heat stress at the seedling stage. Analysis of the H2O2 and proline content revealed that the accumulation rate of H2O2 was higher in T21, whereas the accumulation rate of proline was higher in T2 after heat treatment. Meanwhile, transcriptome analysis revealed that several pathways participated in the heat response, including "protein processing in endoplasmic reticulum", "plant hormone signal transduction", and "carbon metabolism". Additionally, our study also revealed that different pathways participate in heat stress responses upon prolonged stress. The pathway of "protein processing in endoplasmic reticulum" plays an important role in stress responses. We found that most genes involved in this pathway were upregulated and peaked at 0.5 or 1 h after heat treatment. Moreover, sixty transcription factors, including the members of the AP2/ERF, NAC, HSF, WRKY, and C2H2 families, were found to participate in the heat stress response. Many of them have also been reported to be involved in biotic or abiotic stresses. In addition, through PPI (protein-protein interactions) analysis, 22 genes were identified as key genes in the response to heat stress. This study improves our understanding of thermotolerance mechanisms in rice, and also lays a foundation for breeding thermotolerant cultivars via molecular breeding.

Vesicle trafficking in rice: too little is known

The vesicle trafficking apparatus is a fundamental machinery to maintain the homeostasis of membrane-enclosed organelles in eukaryotic cells. Thus, it is broadly conserved in eukaryotes including plants. Intensive studies in the model organisms have produced a comprehensive picture of vesicle trafficking in yeast and human. However, with respect to the vesicle trafficking of plants including rice, our understanding of the components and their coordinated regulation is very limited. At present, several vesicle trafficking apparatus components and cargo proteins have been identified and characterized in rice, but there still remain large unknowns concerning the organization and function of the rice vesicle trafficking system. In this review, we outline the main vesicle trafficking pathways of rice based on knowledge obtained in model organisms, and summarize current advances of rice vesicle trafficking. We also propose to develop methodologies applicable to rice and even other crops for further exploring the mysteries of vesicle trafficking in plants.

Epigenetic and transcription factors synergistically promote the high temperature response in plants

Temperature is one of the main environmental cues affecting plant growth and development, and plants have evolved multiple mechanisms to sense and acclimate to high temperature. Emerging research has shown that transcription factors, epigenetic factors, and their coordination are essential for plant temperature responses and the resulting phenological adaptation. Here, we summarize recent advances in molecular and cellular mechanisms to understand how plants acclimate to high temperature and describe how plant meristems sense and integrate environmental signals. Furthermore, we lay out future directions for new technologies to reveal heterogeneous responses in different cell types thus improving plant environmental plasticity.

Regulatory network of rice in response to heat stress and its potential application in breeding strategy

The rapid development of global industrialization has led to serious environmental problems, among which global warming has become one of the major concerns. The gradual rise in global temperature resulted in the loss of food production, and hence a serious threat to world food security. Rice is the main crop for approximately half of the world's population, and its geographic distribution, yield, and quality are frequently reduced due to elevated temperature stress, and breeding rice varieties with tolerance to heat stress is of immense significance. Therefore, it is critical to study the molecular mechanism of rice in response to heat stress. In the last decades, large amounts of studies have been conducted focusing on rice heat stress response. Valuable information has been obtained, which not only sheds light on the regulatory network underlying this physiological process but also provides some candidate genes for improved heat tolerance breeding in rice. In this review, we summarized the studies in this field. Hopefully, it will provide some new insights into the mechanisms of rice under high temperature stress and clues for future engineering breeding of improved heat tolerance rice.

Constitutive expression of nucleotide-binding and leucine-rich repeat gene AtRPS2 enhanced drought and salt tolerance in rice

Drought and salt are major abiotic stresses that severely restricts plant growth and development, leading to serious losses in agricultural production. Therefore, improving crop tolerance to drought and salt stresses is an urgent issue. A previous study showed that overexpression of Arabidopsis NLR gene AtRPS2 conferred broad-spectrum disease resistance in rice. In this study, we demonstrated that constitutive expression of AtRPS2 increased abscisic acid (ABA) sensitivity during seedling stage, the shoot length of transgenic plants were shorter than wild type plants. Exogenous application of ABA markedly induced the expression of stress-related genes and promoted stomatal close in transgenic plants. Overexpression of AtRPS2 also enhanced drought and salt tolerance in rice, transgenic plants exhibited higher survival rates under drought and salt conditions than wild type plants. The activities of catalase (CAT) and superoxide dismutase (SOD) were higher in AtRPS2 transgenic rice than wild type plants. In addition, the expression of stress-related genes and ABA-responsive genes were significantly upregulated in AtRPS2 transgenic plants than wild type plants under drought and salt treatments. Besides, exogenous application of ABA could facilitate drought and salt tolerance in AtRPS2 transgenic plants. Taken together, this study indicated that AtRPS2 could improve drought and salt tolerance in rice, and this phenomenon is likely to be regulated through ABA signaling pathways.

RGA1 Negatively Regulates Thermo-tolerance by Affecting Carbohydrate Metabolism and the Energy Supply in Rice

BACKGROUND

Signal transduction mediated by heterotrimeric G proteins, which comprise the α, β, and γ subunits, is one of the most important signaling pathways in rice plants. RGA1, which encodes the Gα subunit of the G protein, plays an important role in the response to various types of abiotic stress, including salt, drought, and cold stress. However, the role of RGA1 in the response to heat stress remains unclear.

RESULTS

The heat-resistant mutant ett1 (enhanced thermo-tolerance 1) with a new allele of the RGA1 gene was derived from an ethane methyl sulfonate-induced Zhonghua11 mutant. After 45 °C heat stress treatment for 36 h and recovery for 7 d, the survival rate of the ett1 mutants was significantly higher than that of wild-type (WT) plants. The malondialdehyde content was lower, and the maximum fluorescence quantum yield of photosystem II, peroxidase activity, and hsp expression were higher in ett1 mutants than in WT plants after 12 h of exposure to 45 °C. The RNA-sequencing results revealed that the expression of genes involved in the metabolism of carbohydrate, nicotinamide adenine dinucleotide, and energy was up-regulated in ett1 under heat stress. The carbohydrate content and the relative expression of genes involved in sucrose metabolism indicated that carbohydrate metabolism was accelerated in ett1 under heat stress. Energy parameters, including the adenosine triphosphate (ATP) content and the energy charge, were significantly higher in the ett1 mutants than in WT plants under heat stress. Importantly, exogenous glucose can alleviate the damages on rice seedling plants caused by heat stress.

CONCLUSION

RGA1 negatively regulates the thermo-tolerance in rice seedling plants through affecting carbohydrate and energy metabolism.

Exogenous Methyl Jasmonate Mediated MiRNA-mRNA Network Improves Heat Tolerance of Perennial Ryegrass

Heat stress can hinder the growth of perennial ryegrass (Lolium perenne L.). Methyl jasmonate (MeJA) applied exogenously can increase heat stress tolerance in plants; however, the regulatory mechanisms involved in heat tolerance mediated by MeJA are poorly understood in perennial ryegrass. Here, the microRNA (miRNA) expression profiles of perennial ryegrass were assessed to elucidate the regulatory pathways associated with heat tolerance induced by MeJA. Plants were subjected to four treatments, namely, control (CK), MeJA pre-treatment (T), heat stress treatment (H), and MeJA pre-treatment + heat stress (TH). According to the results, 102 miRNAs were up-regulated in all treatments, with 20, 27, and 33 miRNAs being up-regulated in the T, H, and TH treatment groups, respectively. The co-expression network analysis between the deferentially expressed miRNAs and their corresponding target genes showed that 20 miRNAs modulated 51 potential target genes. Notably, the miRNAs that targeted genes related to with regards to heat tolerance were driven by MeJA, and they were involved in four pathways: novel-m0258-5p mediated signal transduction, novel-m0350-5p mediated protein homeostasis, miR397-z, miR5658-z, and novel-m0008-5p involved in cell wall component, and miR1144-z and miR5185-z dominated chlorophyll degradation. Overall, the findings of this research paved the way for more research into the heat tolerance mechanism in perennial ryegrass and provided a theoretical foundation for developing cultivars with enhanced heat tolerance.

The Regulatory Network of Sweet Corn (Zea mays L.) Seedlings under Heat Stress Revealed by Transcriptome and Metabolome Analysis

Heat stress is an increasingly significant abiotic stress factor affecting crop yield and quality. This study aims to uncover the regulatory mechanism of sweet corn response to heat stress by integrating transcriptome and metabolome analyses of seedlings exposed to normal (25 °C) or high temperature (42 °C). The transcriptome results revealed numerous pathways affected by heat stress, especially those related to phenylpropanoid processes and photosynthesis, with 102 and 107 differentially expressed genes (DEGs) identified, respectively, and mostly down-regulated in expression. The metabolome results showed that 12 or 24 h of heat stress significantly affected the abundance of metabolites, with 61 metabolites detected after 12 h and 111 after 24 h, of which 42 metabolites were detected at both time points, including various alkaloids and flavonoids. Scopoletin-7-o-glucoside (scopolin), 3-indolepropionic acid, acetryptine, 5,7-dihydroxy-3',4',5'-trimethoxyflavone, and 5,6,7,4'-tetramethoxyflavanone expression levels were mostly up-regulated. A regulatory network was built by analyzing the correlations between gene modules and metabolites, and four hub genes in sweet corn seedlings under heat stress were identified: RNA-dependent RNA polymerase 2 (RDR2), UDP-glucosyltransferase 73C5 (UGT73C5), LOC103633555, and CTC-interacting domain 7 (CID7). These results provide a foundation for improving sweet corn development through biological intervention or genome-level modulation.

Rescuing the Golgi from heat damages by ATG8: restoration rather than clean-up

High temperature stress poses significant adverse effects on crop yield and quality. Yet the molecular mechanisms underlying heat stress tolerance in plants/crops, especially regarding the organellar remodeling and homeostasis, are largely unknown. In a recent study, Zhou et al. reported that autophagy-related 8 (ATG8), a famous regulator involved in autophagy, plays a new role in Golgi restoration upon heat stress. Golgi apparatus is vacuolated following short-term acute heat stress, and ATG8 is translocated to the dilated Golgi membrane and interacts with CLATHRIN LIGHT CHAIN 2 (CLC2) to facilitate Golgi restoration, which is dependent on the ATG conjugation system, but not of the upstream autophagic initiators. These exciting findings broaden the fundamental role of ATG8, and elucidate the organelle-level restoration mechanism of Golgi upon heat stress in plants.

Autophagy and multivesicular body pathways cooperate to protect sulfur assimilation and chloroplast functions

Autophagy and multivesicular bodies (MVBs) represent 2 closely related lysosomal/vacuolar degradation pathways. In Arabidopsis (Arabidopsis thaliana), autophagy is stress-induced, with deficiency in autophagy causing strong defects in stress responses but limited effects on growth. LYST-INTERACTING PROTEIN 5 (LIP5) is a key regulator of stress-induced MVB biogenesis, and mutation of LIP5 also strongly compromises stress responses with little effect on growth in Arabidopsis. To determine the functional interactions of these 2 pathways in Arabidopsis, we generated mutations in both the LIP5 and AUTOPHAGY-RELATED PROTEIN (ATG) genes. atg5/lip5 and atg7/lip5 double mutants displayed strong synergistic phenotypes in fitness characterized by stunted growth, early senescence, reduced survival, and greatly diminished seed production under normal growth conditions. Transcriptome and metabolite analysis revealed that chloroplast sulfate assimilation was specifically downregulated at early seedling stages in the atg7/lip5 double mutant prior to the onset of visible phenotypes. Overexpression of adenosine 5'-phosphosulfate reductase 1, a key enzyme in sulfate assimilation, substantially improved the growth and fitness of the atg7/lip5 double mutant. Comparative multi-omic analysis further revealed that the atg7/lip5 double mutant was strongly compromised in other chloroplast functions including photosynthesis and primary carbon metabolism. Premature senescence and reduced survival of atg/lip5 double mutants were associated with increased accumulation of reactive oxygen species and overactivation of stress-associated programs. Blocking PHYTOALEXIN DEFICIENT 4 and salicylic acid signaling prevented early senescence and death of the atg7/lip5 double mutant. Thus, stress-responsive autophagy and MVB pathways play an important cooperative role in protecting essential chloroplast functions including sulfur assimilation under normal growth conditions to suppress salicylic-acid-dependent premature cell-death and promote plant growth and fitness.

An E2-E3 pair contributes to seed size control in grain crops

Understanding the molecular mechanisms that regulate grain yield is important for improving agricultural productivity. Protein ubiquitination controls various aspects of plant growth but lacks understanding on how E2-E3 enzyme pairs impact grain yield in major crops. Here, we identified a RING-type E3 ligase SGD1 and its E2 partner SiUBC32 responsible for grain yield control in Setaria italica. The conserved role of SGD1 was observed in wheat, maize, and rice. Furthermore, SGD1 ubiquitinates the brassinosteroid receptor BRI1, stabilizing it and promoting plant growth. Overexpression of an elite SGD1 haplotype improved grain yield by about 12.8% per plant, and promote complex biological processes such as protein processing in endoplasmic reticulum, stress responses, photosystem stabilization, and nitrogen metabolism. Our research not only identifies the SiUBC32-SGD1-BRI1 genetic module that contributes to grain yield improvement but also provides a strategy for exploring key genes controlling important traits in Poaceae crops using the Setaria model system.

The application of zinc oxide nanoparticles: An effective strategy to protect rice from rice blast and abiotic stresses

The causal agent of blast disease, the filamentous fungus Magnaporthe oryzae, leads to tremendous damage on rice production worldwide. Zinc oxide nanoparticles (ZnO NPs) have multi-functions in plant growth and antimicrobial activity. However, the effects of ZnO NPs on M. oryzae and disease resistance in rice are still unclear. Here, we showed that ZnO NPs have direct antifungal activity against M. oryzae by inhibiting its conidiation and appressorium formation. In addition, ZnO NPs significantly inhibit blast development and enhance basal resistance in rice by inducing ROS accumulation and expression of defense-related genes OsNAC4, OsPR10, OsKSL4, and OsPR1b. Furthermore, we showed that ZnO NPs treatment reduces ABA level in plant, leading to increased ROS accumulation and enhanced resistance against M. oryzae. Importantly, ZnO NPs treatment improves the tolerance of rice seedlings to osmotic and heat stresses.In conclusion, not only being an effective aid in fighting against blast disease, ZnO NPs also provides a novel strategy to enhance the tolerance of rice seedlings to abiotic stress.

Utilization of natural alleles for heat adaptability QTLs at the flowering stage in rice

BACKGROUND

Heat stress threatens rice yield and quality at flowering stage. In this study, average relative seed setting rate under heat stress (RHSR) and genotypes of 284 varieties were used for a genome-wide association study.

RESULTS

We identified eight and six QTLs distributed on chromosomes 1, 3, 4, 5, 7 and 12 in the full population and indica, respectively. qHTT4.2 was detected in both the full population and indica as an overlapping QTL. RHSR was positively correlated with the accumulation of heat-tolerant superior alleles (SA), and indica accession contained at least two heat-tolerant SA with average RHSR greater than 43%, meeting the needs of stable production and heat-tolerant QTLs were offer yield basic for chalkiness degree, amylose content, gel consistency and gelatinization temperature. Chalkiness degree, amylose content, and gelatinization temperature under heat stress increased with accumulation of heat-tolerant SA. Gel consistency under heat stress decreased with polymerization of heat-tolerant SA. The study revealed qHTT4.2 as a stable heat-tolerant QTL that can be used for breeding that was detected in the full population and indica. And the grain quality of qHTT4.2-haplotype1 (Hap1) with chalk5, wx, and alk was better than that of qHTT4.2-Hap1 with CHALK5, WX, and ALK. Twelve putative candidate genes were identified for qHTT4.2 that enhance RHSR based on gene expression data and these genes were validated in two groups. Candidate genes LOC_Os04g52830 and LOC_Os04g52870 were induced by high temperature.

CONCLUSIONS

Our findings identify strong heat-tolerant cultivars and heat-tolerant QTLs with great potential value to improve rice tolerance to heat stress, and suggest a strategy for the breeding of yield-balance-quality heat-tolerant crop varieties.

The MYB transcription factor Seed Shattering 11 controls seed shattering by repressing lignin synthesis in African rice

African cultivated rice (Oryza glaberrima Steud.) was domesticated from its wild progenitor species (Oryza barthii) about 3000 years ago. Seed shattering is one of the main constraints on grain production in African cultivated rice, which causes severe grain losses during harvest. By contrast, Asian cultivated rice (Oryza sativa) displays greater resistance to seed shattering, allowing higher grain production. A better understanding in regulation of seed shattering would help to improve harvesting efficiency in African cultivated rice. Here, we report the map-based cloning and characterization of OgSH11, a MYB transcription factor controlling seed shattering in O. glaberrima. OgSH11 represses the expression of lignin biosynthesis genes and lignin deposition by binding to the promoter of GH2. We successfully developed a new O. glaberrima material showing significantly reduced seed shattering by knockout of SH11 in O. glaberrima using CRISPR-Cas9 mediated approach. Identification of SH11 not only supplies a new target for seed shattering improvement in African cultivated rice, but also provides new insights into the molecular mechanism of abscission layer development.

Reducing brassinosteroid signalling enhances grain yield in semi-dwarf wheat

Modern green revolution varieties of wheat (Triticum aestivum L.) confer semi-dwarf and lodging-resistant plant architecture owing to the Reduced height-B1b (Rht-B1b) and Rht-D1b alleles1. However, both Rht-B1b and Rht-D1b are gain-of-function mutant alleles encoding gibberellin signalling repressors that stably repress plant growth and negatively affect nitrogen-use efficiency and grain filling2-5. Therefore, the green revolution varieties of wheat harbouring Rht-B1b or Rht-D1b usually produce smaller grain and require higher nitrogen fertilizer inputs to maintain their grain yields. Here we describe a strategy to design semi-dwarf wheat varieties without the need for Rht-B1b or Rht-D1b alleles. We discovered that absence of Rht-B1 and ZnF-B (encoding a RING-type E3 ligase) through a natural deletion of a haploblock of about 500 kilobases shaped semi-dwarf plants with more compact plant architecture and substantially improved grain yield (up to 15.2%) in field trials. Further genetic analysis confirmed that the deletion of ZnF-B induced the semi-dwarf trait in the absence of the Rht-B1b and Rht-D1b alleles through attenuating brassinosteroid (BR) perception. ZnF acts as a BR signalling activator to facilitate proteasomal destruction of the BR signalling repressor BRI1 kinase inhibitor 1 (TaBKI1), and loss of ZnF stabilizes TaBKI1 to block BR signalling transduction. Our findings not only identified a pivotal BR signalling modulator but also provided a creative strategy to design high-yield semi-dwarf wheat varieties by manipulating the BR signal pathway to sustain wheat production.

ENHANCED DISEASE SUSCEPTIBILITY 1 promotes hydrogen peroxide scavenging to enhance rice thermotolerance

Heat stress is a major factor limiting the production and geographic distribution of rice (Oryza sativa), and breeding rice varieties with tolerance to heat stress is of immense importance. Although extensive studies have revealed that reactive oxygen species (ROS) play a critical role in rice acclimation to heat stress, the molecular basis of rice controlling ROS homeostasis remains largely unclear. In this study, we discovered a novel heat stress-responsive strategy that orchestrates ROS homeostasis centering on an immune activator, rice ENHANCED DISEASE SUSCEPTIBILITY 1 (OsEDS1). OsEDS1, which confers heat stress tolerance, promotes hydrogen peroxide (H2O2) scavenging by stimulating catalase activity through the OsEDS1-catalase association. The loss-of-function mutation in OsEDS1 causes increased sensitivity to heat stress, whereas overexpression of OsEDS1 enhances thermotolerance. Furthermore, overexpression lines greatly improved rice tolerance to heat stress during the reproductive stage, which was associated with substantially increased seed setting, grain weight, and plant yield. Rice CATALASE C (OsCATC), whose activity is promoted by OsEDS1, degrades H2O2 to activate rice heat stress tolerance. Our findings greatly expand our understanding of heat stress responses in rice. We reveal a molecular framework that promotes heat tolerance through ROS homeostasis regulation, suggesting a theoretical basis and providing genetic resources for breeding heat-tolerant rice varieties.