An α/β hydrolase family member negatively regulates salt tolerance but promotes flowering through three distinct functions in rice

The antisense CircRNA VvcircABH controls salt tolerance and the brassinosteroid signaling response by suppressing cognate mRNA splicing in grape

Soil salinization is a major factor limiting the sustainable development of the grape industry. Circular RNAs (circRNAs) are more stable than linear mRNAs and are involved in stress responses. However, the biological functions and molecular mechanisms underlying antisense circRNAs in plants remain unclear. We identified the antisense circRNA VvcircABH through high-throughput sequencing. Using genetic transformation methods and molecular biological techniques, we analyzed the effects of VvcircABH on the response to salt stress and the mechanisms underlying its effects. VvcircABH was located in the nucleus and upregulated by salt stress, while the expression level of its cognate gene VvABH (alpha/beta-hydrolase) was downregulated. VvcircABH overexpression or VvABH silencing greatly enhanced grape salt tolerance. VvcircABH could bind to the overlapping region and inhibits VvABH pre-mRNA splicing, thereby decreasing the expression level of VvABH. Additionally, VvcircABH repressed the additive effect of VvABH on the interaction between VvBRI1 (brassinosteroid-insensitive 1) and VvBKI1 (BRI1 kinase inhibitor 1), thus influencing the plant's response to BR, which plays important roles in plant salt tolerance. We conclude that VvcircABH and VvABH play distinct roles in the salt tolerance and brassinosteroid signaling response, and VvcircABH could govern the expression of VvABH by inhibiting its splicing.

A Series of Novel Alleles of Ehd2 Modulating Heading and Salt Tolerance in Rice

Rice (Oryza sativa L.) is a staple crop for nearly half of the global population and one of China's most extensively cultivated cereals. Heading date, a critical agronomic trait, determines the regional and seasonal adaptability of rice varieties. In this study, a series of mutants (elh5 to elh12) exhibiting extremely late heading under both long-day (LD) and short-day (SD) conditions were identified from an ethyl methanesulfonate (EMS) mutant library. Using MutMap and map-based cloning, the causative gene was identified as a novel allele of Ehd2/OsID1/RID1/Ghd10. Functional validation through CRISPR/Cas9 knockout and complementation assays confirmed its role in regulating heading. The elh6 mutation was found to cause intron retention due to alternative splicing. Ehd2 encodes a Cys-2/His-2-type zinc finger transcription factor with an IDD domain and transcriptional activity in yeast. Its expression peaks in developing leaves before heading and spikes during reproductive conversion. In elh6 mutants, delayed heading resulted from downregulating the Ehd1-Hd3a pathway genes. Salinity stress significantly hampers rice growth and productivity. Transcriptomic analysis of elh10 and ZH8015 seedlings exposed to salt stress for 24 h identified 5150 differentially expressed genes (DEGs) at the seedling stage, predominantly linked to stress response pathways. Ehd2 was revealed as a modulator of salt tolerance, likely through the regulation of ion transport, enzyme activity, and antioxidant systems. This study establishes Ehd2 as a pivotal factor in promoting heading while negatively regulating salt tolerance in rice.

OsWNK9 mitigates salt stress by promoting root growth and stomatal closure in rice

Salinity stress severely affects rice growth and reduces its productivity. With No Lysine Kinases (WNKs) are serine/threonine kinases emerging as potential candidate genes due to their involvement in various abiotic stress tolerance responses. However, studies providing mechanistic insights into the roles of WNKs in plants remain scarce. In the present study, OsWNK9-overexpressing rice lines showed strong tolerance to salinity stress. Overexpression of OsWNK9 also triggered the accumulation of abscisic acid (ABA) and restored indole-3-acetic acid (IAA) concentrations in roots, triggering stomatal closure in shoots and maintaining cell expansion of the root epidermal cells when challenged with salt treatment. The overexpression lines showed increased activity of antioxidant enzymes, which further mitigated ROS-mediated cellular damage under salinity stress. We also identified that OsWNK9 interacts with Receptor for Activated Kinase C1A (RACK1A), ABA-8'-hydroxylase, and (Vacuolar Type ATPase) V-Type ATPase. Taken together, our findings suggest that OsWNK9 expression is warranted under salinity stress and exerts its effects by interacting with its downstream targets and by increased accumulation of ABA and IAA, thereby regulating seed germination, stomatal activity, improved root growth, and ionic homeostasis, which all contribute to significantly higher yield produced per plant under long term salinity stress.

Molecular Basis of Lipid Metabolism in Oryza sativa L

Lipids are the basic biological molecules in plants, serving as glycerolipids for cell membranes and triacylglycerols as an energy source. Fatty acids are the major components of plant lipids. Both lipids and fatty acids significantly influence rice quality. Recent studies, through genetic analysis, have made significant progress in uncovering the functional mechanisms and regulatory pathways of lipid metabolism including the biological synthesis and degradation of fatty acids, glycerolipids, and triacylglycerols in rice. Meanwhile, quantitative trait loci (QTLs) identified by analyzing the natural variations of the composition and contents of lipids and fatty acids have been integrated and represented on 12 chromosomes. Lipids play multifaceted roles in the growth and development and stress response of rice. Through metabolic engineering and gene-editing technologies, significant advancements have been made in improving the lipid content in rice grains. These studies highlight the understanding the of molecular basis of lipid metabolism and lay a substantial basis for the genetic improvement of rice quality.

Biological Roles of Lipids in Rice

Lipids are organic nonpolar molecules with essential biological and economic importance. While the genetic pathways and regulatory networks of lipid biosynthesis and metabolism have been extensively studied and thoroughly reviewed in oil crops such as soybeans, less attention has been paid to the biological roles of lipids in rice, a staple food for the global population and a model species for plant molecular biology research, leaving a considerable knowledge gap in the biological roles of lipids. In this review, we endeavor to furnish a current overview of the advancements in understanding the genetic foundations and physiological functions of lipids, including triacylglycerol, fatty acids, and very-long-chain fatty acids. We aim to summarize the key genes in lipid biosynthesis, metabolism, and transcriptional regulation underpinning rice's developmental and growth processes, biotic stress responses, abiotic stress responses, fertility, seed longevity, and recent efforts in rice oil genetic improvement.

Comparative proteomic and metabolomic analyses reveal stress responses of hemp to salinity

KEY MESSAGE

Integrated omics analyses outline the cellular and metabolic events of hemp plants in response to salt stress and highlight several photosynthesis and energy metabolism related pathways as key regulatory points. Soil salinity affects many physiological processes of plants and leads to crop yield losses worldwide. For hemp, a crop that is valued for multiple aspects, such as its medical compounds, fibre, and seed, a comprehensive understanding of its salt stress responses is a prerequisite for resistance breeding and tailoring its agronomic performance to suit certain industrial applications. Here, we first observed the phenotype of salt-stressed hemp plants and found that under NaCl treatment, hemp plants displayed pronounced growth defects, as indicated by the significantly reduced average height, number of leaves, and chlorophyll content. Next, we conducted comparative proteomics and metabolomics to dissect the complex salt-stress response mechanisms. A total of 314 proteins and 649 metabolites were identified to be differentially behaving upon NaCl treatment. Functional classification and enrichment analysis unravelled that many differential proteins were proteases associated with photosynthesis. Through metabolic pathway enrichment, several energy-related pathways were found to be altered, such as the biosynthesis and degradation of branched-chain amino acids, and our network analysis showed that many ribosomal proteins were involved in these metabolic adaptations. Taken together, for hemp plants, influences on chloroplast function probably represent a major toxic effect of salinity, and modulating several energy-producing pathways possibly through translational regulation is presumably a key protective mechanism against the negative impacts. Our data and analyses provide insights into our understanding of hemp's stress biology and may lay a foundation for future functional genomics studies.

Uncovering key salt-tolerant regulators through a combined eQTL and GWAS analysis using the super pan-genome in rice

For sessile plants, gene expression plays a pivotal role in responding to salinity stress by activating or suppressing specific genes. However, our knowledge of genetic variations governing gene expression in response to salt stress remains limited in natural germplasm. Through transcriptome analysis of the Global Mini-Core Rice Collection consisting of a panel of 202 accessions, we identified 22 345 and 27 610 expression quantitative trait loci associated with the expression of 7787 and 9361 eGenes under normal and salt-stress conditions, respectively, leveraging the super pan-genome map. Notably, combined with genome-wide association studies, we swiftly pinpointed the potential candidate gene STG5-a major salt-tolerant locus known as qSTS5. Intriguingly, STG5 is required for maintaining Na+/K+ homeostasis by directly regulating the transcription of multiple members of the OsHKT gene family. Our study sheds light on how genetic variants influence the dynamic changes in gene expression responding to salinity stress and provides a valuable resource for the mining of salt-tolerant genes in the future.

Designing salt stress-resilient crops: Current progress and future challenges

Excess soil salinity affects large regions of land and is a major hindrance to crop production worldwide. Therefore, understanding the molecular mechanisms of plant salt tolerance has scientific importance and practical significance. In recent decades, studies have characterized hundreds of genes associated with plant responses to salt stress in different plant species. These studies have substantially advanced our molecular and genetic understanding of salt tolerance in plants and have introduced an era of molecular design breeding of salt-tolerant crops. This review summarizes our current knowledge of plant salt tolerance, emphasizing advances in elucidating the molecular mechanisms of osmotic stress tolerance, salt-ion transport and compartmentalization, oxidative stress tolerance, alkaline stress tolerance, and the trade-off between growth and salt tolerance. We also examine recent advances in understanding natural variation in the salt tolerance of crops and discuss possible strategies and challenges for designing salt stress-resilient crops. We focus on the model plant Arabidopsis (Arabidopsis thaliana) and the four most-studied crops: rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), and soybean (Glycine max).

Dysfunction of duplicated pair rice histone acetyltransferases causes segregation distortion and an interspecific reproductive barrier

Postzygotic reproductive isolation, which results in the irreversible divergence of species, is commonly accompanied by hybrid sterility, necrosis/weakness, or lethality in the F1 or other offspring generations. Here we show that the loss of function of HWS1 and HWS2, a couple of duplicated paralogs, together confer complete interspecific incompatibility between Asian and African rice. Both of these non-Mendelian determinants encode the putative Esa1-associated factor 6 (EAF6) protein, which functions as a characteristic subunit of the histone H4 acetyltransferase complex regulating transcriptional activation via genome-wide histone modification. The proliferating tapetum and inappropriate polar nuclei arrangement cause defective pollen and seeds in F2 hybrid offspring due to the recombinant HWS1/2-mediated misregulation of vitamin (biotin and thiamine) metabolism and lipid synthesis. Evolutionary analysis of HWS1/2 suggests that this gene pair has undergone incomplete lineage sorting (ILS) and multiple gene duplication events during speciation. Our findings have not only uncovered a pair of speciation genes that control hybrid breakdown but also illustrate a passive mechanism that could be scaled up and used in the guidance and optimization of hybrid breeding applications for distant hybridization.

Integration of Physiological, Transcriptomic, and Metabolomic Analyses Reveal Molecular Mechanisms of Salt Stress in Maclura tricuspidata

Salt stress is a universal abiotic stress that severely affects plant growth and development. Understanding the mechanisms of Maclura tricuspidate's adaptation to salt stress is crucial for developing salt-tolerant plant varieties. This article discusses the integration of physiology, transcriptome, and metabolome to investigate the mechanism of salt adaptation in M. tricuspidata under salt stress conditions. Overall, the antioxidant enzyme system (SOD and POD) of M. tricuspidata exhibited higher activities compared with the control, while the content of soluble sugar and concentrations of chlorophyll a and b were maintained during salt stress. KEGG analysis revealed that deferentially expressed genes were primarily involved in plant hormone signal transduction, phenylpropanoid and flavonoid biosynthesis, alkaloids, and MAPK signaling pathways. Differential metabolites were enriched in amino acid metabolism, the biosynthesis of plant hormones, butanoate, and 2-oxocarboxylic acid metabolism. Interestingly, glycine, serine, and threonine metabolism were found to be important both in the metabolome and transcriptome-metabolome correlation analyses, suggesting their essential role in enhancing the salt tolerance of M. tricuspidata. Collectively, our study not only revealed the molecular mechanism of salt tolerance in M. tricuspidata, but also provided a new perspective for future salt-tolerant breeding and improvement in salt land for this species.

Synergistic optimization of crops by combining early maturation with other agronomic traits

Many newly created early maturing varieties exhibit poor stress resistance and low yield, whereas stress-resistant varieties are typically late maturing. For this reason, the polymerization of early maturity and other desired agronomic qualities requires overcoming the negative connection between early maturity, multi-resistance, and yield, which presents a formidable challenge in current breeding techniques. We review the most salient constraints of early maturity breeding in current crop planting practices and the molecular mechanisms of different maturation timeframes in diverse crops from their origin center to production areas. We explore current breeding tactics and the future direction of crop breeding and the issues that must be resolved to accomplish the polymerization of desirable traits in light of the current obstacles and limitations.

Sterile line Dexiang074A enhances drought tolerance in hybrid rice

Heterosis has been widely used in rice breeding, especially in improving rice yield. But it has rarely been studied in rice abiotic stress, including the drought tolerance, which is becoming one of the most important threaten in decreasing rice yield. Therefore, it is essential to studying the mechanism underlying heterosis in improving drought tolerance of rice breeding. In this study, Dexiang074B (074B) and Dexiang074A (074A) served as maintainer lines and sterile lines. Mianhui146 (R146), Chenghui727 (R727), LuhuiH103 (RH103), Dehui8258 (R8258), Huazhen (HZ), Dehui938 (R938), Dehui4923 (R4923), and R1391 served as restorer lines. The progeny were Dexiangyou (D146), Deyou4727 (D4727), Dexiang 4103 (D4103), Deyou8258 (D8258), Deyou Huazhen (DH), Deyou 4938 (D4938), Deyou 4923 (D4923), and Deyou 1391 (D1391). The restorer line and hybrid offspring were subjected to drought stress at the flowering stage. The results showed that Fv/Fm values were abnormal and oxidoreductase activity and MDA content were increased. However, the performance of hybrid progeny was significantly better than their respective restorer lines. Although the yield of hybrid progeny and restorer lines decreased simultaneously, the yield in hybrid offspring is significantly lower than the respective restorer line. Total soluble sugar content was consistent with the yield result, so we found that 074A can enhance drought tolerance in hybrid rice.