A MITE variation-associated heat-inducible isoform of a heat-shock factor confers heat tolerance through regulation of JASMONATE ZIM-DOMAIN genes in rice

Heat stress transcription factors as the central molecular rheostat to optimize plant survival and recovery from heat stress

Heat stress transcription factors (HSFs) are the core regulators of the heat stress (HS) response in plants. HSFs are considered as a molecular rheostat: their activities define the response intensity, incorporating information about the environmental temperature through a network of partner proteins. A prompted activation of HSFs is required for survival, for example the de novo synthesis of heat shock proteins. Furthermore, a timely attenuation of the stress response is necessary for the restoration of cellular functions and recovery from stress. In an ever-changing environment, the balance between thermotolerance and developmental processes such as reproductive fitness highlights the importance of a tightly tuned response. In many cases, the response is described as an ON/OFF mode, while in reality, it is very dynamic. This review compiles recent findings to update existing models about the HSF-regulated HS response and address two timely questions: How do plants adjust the intensity of cellular HS response corresponding to the temperature they experience? How does this adjustment contribute to the fine-tuning of the HS and developmental networks? Understanding these processes is crucial not only for enhancing our basic understanding of plant biology but also for developing strategies to improve crop resilience and productivity under stressful conditions.

Long noncoding RNAs underlie multiple domestication traits and leafhopper resistance in soybean

The origin and functionality of long noncoding RNA (lncRNA) remain poorly understood. Here, we show that multiple quantitative trait loci modulating distinct domestication traits in soybeans are pleiotropic effects of a locus composed of two tandem lncRNA genes. These lncRNA genes, each containing two inverted repeats, originating from coding sequences of the MYB genes, function in wild soybeans by generating clusters of small RNA (sRNA) species that inhibit the expression of their MYB gene relatives through post-transcriptional regulation. By contrast, the expression of lncRNA genes in cultivated soybeans is severely repressed, and, consequently, the corresponding MYB genes are highly expressed, shaping multiple distinct domestication traits as well as leafhopper resistance. The inverted repeats were formed before the divergence of the Glycine genus from the Phaseolus-Vigna lineage and exhibit strong structure-function constraints. This study exemplifies a type of target for selection during plant domestication and identifies mechanisms of lncRNA formation and action.

Early signaling enhance heat tolerance in Arabidopsis through modulating jasmonic acid synthesis mediated by HSFA2

Given the detrimental impact of global warming on crop production, it is particularly important to understand how plants respond and adapt to higher temperatures. Using the non-invasive micro-test technique and laser confocal microscopy, we found that the cascade process of early signals (K+, H2O2, H+, and Ca2+) ultimately resulted in an increase in the cytoplasmic Ca2+ concentration when Arabidopsis was exposed to heat stress. Quantitative real-time PCR demonstrated that heat stress significantly up-regulated the expression of CAM1, CAM3 and HSFA2; however, after CAM1 and CAM3 mutation, the upregulation of HSFA2 was reduced. In addition, heat stress affected the expression of LOX3 and OPR3, which was not observed when HSFA2 was mutated. Luciferase reporter gene expression assay and electrophoretic mobility shift assay showed that HSFA2 regulated the expression of both genes. Determination of jasmonic acid (JA) content showed that JA synthesis was promoted by heat stress, but was damaged when HSFA2 and OPR3 were mutated. Finally, physiological experiments showed that JA reduced the relative electrical conductivity of leaves, enhanced chlorophyll content and relative water content, and improved the survival rate of Arabidopsis under heat stress. Together, our results reveal a new pathway for Arabidopsis to sense and transmit heat signals; HSFA2 is involved in the JA synthesis, which can act as a defensive compound improving Arabidopsis heat tolerance.

Transposable elements cause the loss of self-incompatibility in citrus

Self-incompatibility (SI) is a widespread prezygotic mechanism for flowering plants to avoid inbreeding depression and promote genetic diversity. Citrus has an S-RNase-based SI system, which was frequently lost during evolution. We previously identified a single nucleotide mutation in Sm-RNase, which is responsible for the loss of SI in mandarin and its hybrids. However, little is known about other mechanisms responsible for conversion of SI to self-compatibility (SC) and we identify a completely different mechanism widely utilized by citrus. Here, we found a 786-bp miniature inverted-repeat transposable element (MITE) insertion in the promoter region of the FhiS2-RNase in Fortunella hindsii Swingle (a model plant for citrus gene function), which does not contain the Sm-RNase allele but are still SC. We demonstrate that this MITE plays a pivotal role in the loss of SI in citrus, providing evidence that this MITE insertion prevents expression of the S-RNase; moreover, transgenic experiments show that deletion of this 786-bp MITE insertion recovers the expression of FhiS2-RNase and restores SI. This study identifies the first evidence for a role for MITEs at the S-locus affecting the SI phenotype. A family-wide survey of the S-locus revealed that MITE insertions occur frequently adjacent to S-RNase alleles in different citrus genera, but only certain MITEs appear to be responsible for the loss of SI. Our study provides evidence that insertion of MITEs into a promoter region can alter a breeding strategy and suggests that this phenomenon may be broadly responsible for SC in species with the S-RNase system.

Utilization of the Winkler scale of plants using big data temperature presented by the Korea Meteorological Administration

Introduction

Rice is an important food source that can provide a stable supply of calories for most people around the world. However, owing to the recent rapid temperature rise, we are facing social issues related to the increase in the Winkler scale. In this study, a strategy for screening potential candidate genes related to the yield according to the Winkler scale is presented, and the possibility of using a candidate gene identified through sequence haplotype and homology analysis as a breeding source is suggested.

Methods

QTL for the Winkler scale was identified using a population of 120 double haploids derived from a cross between Cheongchoneg, Indica, and Nagdong, Japonica.

Results and discussion

A total of 79 candidate genes were detected in the identified QTL region, and OsHAq8 was finally screened. Through haplotype analysis, OsHAq8 was derived from the Indica group and orthologous to Graminae's activator of Hsp90 ATPase, suggesting that it is a candidate gene involved in yield according to temperature during the growing period. The expression level of OsHAq8 increased as the Winkler scale increased. The findings of this study can serve as a crucial indicator for predicting harvest time and grain quality while achieving a stable yield through marker selection and adaptation to climate change. Climate change occurs more frequently. In these situations, it is very important to predict harvest time and apply relevant candidate genes to breeding. The candidate genes presented in this study can be effectively applied to rice breeding in preparation for climate change.

Genome-Wide Identification and Functional Analysis of the TIFY Family Genes in Response to Abiotic Stresses and Hormone Treatments in Tartary Buckwheat (Fagopyrum tataricum)

TIFY is a plant-specific gene family with four subfamilies: ZML, TIFY, PPD, and JAZ. Recently, this family was found to have regulatory functions in hormone stimulation, environmental response, and development. However, little is known about the roles of the TIFY family in Tartary buckwheat (Fagopyrum tataricum), a significant crop for both food and medicine. In this study, 18 TIFY family genes (FtTIFYs) in Tartary buckwheat were identified. The characteristics, motif compositions, and evolutionary relationships of the TIFY proteins, as well as the gene structures, cis-acting elements, and synteny of the TIFY genes, are discussed in detail. Moreover, we found that most FtTIFYs responded to various abiotic stresses (cold, heat, salt, or drought) and hormone treatments (ABA, MeJA, or SA). Through yeast two-hybrid assays, we revealed that two FtTIFYs, FtTIFY1 and FtJAZ7, interacted with FtABI5, a homolog protein of AtABI5 involved in ABA-mediated germination and stress responses, implying crosstalk between ABA and JA signaling in Tartary buckwheat. Furthermore, the overexpression of FtJAZ10 and FtJAZ12 enhanced the heat stress tolerance of tobacco. Consequently, our study suggests that the FtTIFY family plays important roles in responses to abiotic stress and provides two candidate genes (FtJAZ10 and FtJAZ12) for the cultivation of stress-resistant crops.

The CsHSFA-CsJAZ6 module-mediated high temperature regulates flavonoid metabolism in Camellia sinensis

High temperatures (HTs) seriously affect the yield and quality of tea. Catechins, derived from the flavonoid pathway, are characteristic compounds that contribute to the flavour of tea leaves. In this study, we first showed that the flavonoid content of tea leaves was significantly reduced under HT conditions via metabolic profiles; and then demonstrated that two transcription factors, CsHSFA1b and CsHSFA2 were activated by HT and negatively regulate flavonoid biosynthesis during HT treatment. Jasmonate (JA), a defensive hormone, plays a key role in plant adaption to environmental stress. However, little has been reported on its involvement in HT response in tea. Herein, we demonstrated that CsHSFA1b and CsHSFA2 activate CsJAZ6 expression through directly binding to heat shock elements in its promoter, and thereby repress the JA pathway. Most secondary metabolites are regulated by JA, including catechin in tea. Our study reported that CsJAZ6 directly interacts with CsEGL3 and CsTTG1 and thereby reduces catechin accumulation. From this, we proposed a CsHSFA-CsJAZ6-mediated HT regulation model of catechin biosynthesis. We also determined that negative regulation of the JA pathway by CsHSFAs and its homologues is conserved in Arabidopsis. These findings broaden the applicability of the regulation of JAZ by HSF transcription factors and further suggest the JA pathway as a valuable candidate for HT-resistant breeding and cultivation.

The hot science in rice research: How rice plants cope with heat stress

Global climate change has great impacts on plant growth and development, reducing crop productivity worldwide. Rice (Oryza sativa L.), one of the world's most important food crops, is susceptible to high-temperature stress from seedling stage to reproductive stage. In this review, we summarize recent advances in understanding the molecular mechanisms underlying heat stress responses in rice, including heat sensing and signalling, transcriptional regulation, transcript processing, protein translation, and post-translational regulation. We also highlight the irreversible effects of high temperature on reproduction and grain quality in rice. Finally, we discuss challenges and opportunities for future research on heat stress responses in rice.

How rice adapts to high temperatures

High-temperature stress affects crop yields worldwide. Identifying thermotolerant crop varieties and understanding the basis for this thermotolerance would have important implications for agriculture, especially in the face of climate change. Rice (Oryza sativa) varieties have evolved protective strategies to acclimate to high temperature, with different thermotolerance levels. In this review, we examine the morphological and molecular effects of heat on rice in different growth stages and plant organs, including roots, stems, leaves and flowers. We also explore the molecular and morphological differences among thermotolerant rice lines. In addition, some strategies are proposed to screen new rice varieties for thermotolerance, which will contribute to the improvement of rice for agricultural production in the future.

Polymorphic inverted repeats near coding genes impact chromatin topology and phenotypic traits in Arabidopsis thaliana

Transposons are mobile elements that are commonly silenced to protect eukaryotic genome integrity. In plants, transposable element (TE)-derived inverted repeats (IRs) are commonly found near genes, where they affect host gene expression. However, the molecular mechanisms of such regulation are unclear in most cases. Expression of these IRs is associated with production of 24-nt small RNAs, methylation of the IRs, and drastic changes in local 3D chromatin organization. Notably, many of these IRs differ between Arabidopsis thaliana accessions, causing variation in short-range chromatin interactions and gene expression. CRISPR-Cas9-mediated disruption of two IRs leads to a switch in genome topology and gene expression with phenotypic consequences. Our data show that insertion of an IR near a gene provides an anchor point for chromatin interactions that profoundly impact the activity of neighboring loci. This turns IRs into powerful evolutionary agents that can contribute to rapid adaptation.