Project description:Salt stress is a major constraint on plant growth and yield. Nitrogen (N) fertilizers are known to alleviate salt stress. However, the underlying molecular mechanisms remain unclear. Here, we show that nitrate-dependent salt tolerance is mediated by OsMADS27 in rice. The expression of OsMADS27 is specifically induced by nitrate. The salt-inducible expression of OsMADS27 is also nitrate dependent. OsMADS27 knockout mutants are more sensitive to salt stress than the wild type, whereas OsMADS27 overexpression lines are more tolerant. Transcriptomic analyses revealed that OsMADS27 upregulates the expression of a number of known stress-responsive genes as well as those involved in ion homeostasis and antioxidation. We demonstrate that OsMADS27 directly binds to the promoters of OsHKT1.1 and OsSPL7 to regulate their expression. Notably, OsMADS27-mediated salt tolerance is nitrate dependent and positively correlated with nitrate concentration. Our results reveal the role of nitrate-responsive OsMADS27 and its downstream target genes in salt tolerance, providing a molecular mechanism for the enhancement of salt tolerance by nitrogen fertilizers in rice. OsMADS27 overexpression increased grain yield under salt stress in the presence of sufficient nitrate, suggesting that OsMADS27 is a promising candidate for the improvement of salt tolerance in rice. This study reports that nitrate-responsive OsMADS27 promotes salt tolerance, revealing a molecular mechanism for the enhancement of salt tolerance by nitrogen fertilizers in rice.
Project description:High salinity is a major stress factor affecting the quality and productivity of rice (Oryza sativa L.). Although numerous salt tolerance-related genes have been identified in rice, their molecular mechanisms remain unknown. Here, we report that OsJRL40, a jacalin-related lectin gene, confers remarkable salt tolerance in rice. The loss of function of OsJRL40 increased sensitivity to salt stress in rice, whereas its overexpression enhanced salt tolerance at the seedling stage and during reproductive growth. β-glucuronidase (GUS) reporter assays indicated that OsJRL40 is expressed to higher levels in roots and internodes than in other tissues, and subcellular localization analysis revealed that the OsJRL40 protein localizes to the cytoplasm. Further molecular analyses showed that OsJRL40 enhances antioxidant enzyme activities and regulates Na+-K+ homeostasis under salt stress. RNA-seq analysis revealed that OsJRL40 regulates salt tolerance in rice by controlling the expression of genes encoding Na+/K+ transporters, salt-responsive transcription factors, and other salt response-related proteins. Overall, this study provides a scientific basis for an in-depth investigation of the salt tolerance mechanism in rice and could guide the breeding of salt-tolerant rice cultivars.
Project description:BackgroundRice is a salt-sensitive crop. Complex gene regulatory cascades are likely involved in salinity stress in rice roots. microRNA168 (miR168) is a conserved miRNA among different plant species. It in-directly regulates the expression of all miRNAs by targeting gene ARGONAUTE1(AGO1). Short Tandem Target Mimic (STTM) technology is an ideal approach to study miRNA functions by in-activating mature miRNA in plants.ResultsIn this study, rice miR168 was inactivated by STTM. The T3 generation seedlings of STTM168 exhibited significantly enhanced salt resistance. Direct target genes of rice miR168 were obtained by in silico prediction and further confirmed by degradome-sequencing. PINHEAD (OsAGO1), which was previously suggested to be a plant abiotic stress response regulator. RNA-Seq was performed in root samples of 150mM salt-treated STTM168 and control seedlings. Among these screened 481 differentially expressed genes within STTM168 and the control, 44 abiotic stress response related genes showed significant difference, including four known salt-responsive genes.ConclusionBased on sequencing and qRT-PCR, a "miR168-AGO1-downstream" gene regulation model was proposed to be responsible for rice salt stress response. The present study proved miR168-AGO1 cascade to play important role in rice salinity stress responding, as well as to be applied in agronomic improvement in further.
Project description:High salinity seriously affects crop growth and yield. Abscisic acid-, stress-, and ripening-induced (ASR) proteins play an important role in plant responses to multiple abiotic stresses. In this study, we identified a new salt-induced ASR gene in rice (OsASR6) and functionally characterized its role in mediating salt tolerance. Transcript levels of OsASR6 were upregulated under salinity stress, H2O2 and abscisic acid (ABA) treatments. Nuclear and cytoplasmic localization of the OsASR6 protein were confirmed. Meanwhile, a transactivation activity assay in yeast demonstrated no self-activation ability. Furthermore, transgenic rice plants overexpressing OsASR6 showed enhanced salt and oxidative stress tolerance as a result of reductions in H2O2, malondialdehyde (MDA), Na/K and relative electrolyte leakage. In contrast, OsASR6 RNAi transgenic lines showed opposite results. A higher ABA content was also measured in the OsASR6 overexpressing lines compared with the control. Moreover, OsNCED1, a key enzyme of ABA biosynthesis, was found to interact with OsASR6. Collectively, these results suggest that OsASR6 serves primarily as a functional protein, enhancing tolerance to salt stress, representing a candidate gene for genetic manipulation of new salinity-resistant lines in rice.
Project description:BackgroundSoil salinity is one of the primary environmental stresses faced in rice production. When plants are exposed to salt stress, a series of cellular balances will be disrupted. Dufulin is an immune-induced antiviral agent used in plants. The DUF gene family influences plant response to abiotic stress, and the functional role of OsDUF6(ABA98726.1) in rice response to salt stress is being investigated here.ResultsBased on the transcriptome analysis of Dufulin treatment in inducing salt tolerance in rice, we selected the OsDUF6 protein located on the cell membrane and studied its molecular function by overexpressing OsDUF6. Salt-induced decreases in root, stem, and leaf length and increased leaf yellowing rate and Na+ concentration in the wild-type plant were mitigated in the overexpressed lines. OsDUF6 overexpression increased the enzymatic antioxidant activities of superoxide dismutase, peroxidase, catalase, and phenylalanine ammonia-lyase. OsDUF6 also played a positive role in Na+ transport as reflected by the increased growth of a salt-sensitive yeast mutant complemented with OsDUF6 in the presence of salt stress. In addition, Reverse transcription quantitative PCR analysis confirmed that the overexpression of OsDUF6 significantly changed the expression level of other genes related to growth and stress tolerance.ConclusionsCombined with previously published data, our results supported the observation that OsDUF6 is an important functional factor in Dufulin-induced promotion of salt stress tolerance in rice.
Project description:Expansins are key regulators of cell-wall extension and are also involved in the abiotic stress response. In this study, we evaluated the function of OsEXPA7 involved in salt stress tolerance. Phenotypic analysis showed that OsEXPA7 overexpression remarkably enhanced tolerance to salt stress. OsEXPA7 was highly expressed in the shoot apical meristem, root, and the leaf sheath. Promoter activity of OsEXPA7:GUS was mainly observed in vascular tissues of roots and leaves. Morphological analysis revealed structural alterations in the root and leaf vasculature of OsEXPA7 overexpressing (OX) lines. OsEXPA7 overexpression resulted in decreased sodium ion (Na+) and accumulated potassium ion (K+) in the leaves and roots. Under salt stress, higher antioxidant activity was also observed in the OsEXPA7-OX lines, as indicated by lower reactive oxygen species (ROS) accumulation and increased antioxidant activity, when compared with the wild-type (WT) plants. In addition, transcriptional analysis using RNA-seq and RT-PCR revealed that genes involved in cation exchange, auxin signaling, cell-wall modification, and transcription were differentially expressed between the OX and WT lines. Notably, salt overly sensitive 1, which is a sodium transporter, was highly upregulated in the OX lines. These results suggest that OsEXPA7 plays an important role in increasing salt stress tolerance by coordinating sodium transport, ROS scavenging, and cell-wall loosening.
Project description:The roles of clock components in salt stress tolerance remain incompletely characterized in rice. Here we show that, among OsPRR (Oryza sativa Pseudo-Response Regulator) family members, OsPRR73 specifically confers salt tolerance in rice. Notably, the grain size and yield of osprr73 null mutants were significantly decreased in the presence of salt stress, with accumulated higher level of reactive oxygen species and sodium ions. RNA-sequencing and biochemical assays identified OsHKT2;1, encoding a plasma-membrane localized Na+ transporter, as a transcriptional target of OsPRR73 in mediating salt tolerance. Correspondingly, null mutants of OsHKT2;1 displayed an increased tolerance to salt stress. Immunoprecipitation-mass spectrometry (IP-MS) assays further identified HDAC10 as nuclear interactor of OsPRR73 and co-repressor of OsHKT2;1. Consistently, H3K9ac histone marks at OsHKT2;1 promoter regions were significantly reduced in osprr73 mutant. Together, our findings reveal that salt-induced OsPRR73 expression confers salt tolerance by recruiting HDAC10 to transcriptionally repress OsHKT2;1, thus reducing cellular Na+ accumulation. This exemplifies a new molecular link between clock components and salt stress tolerance in rice.
Project description:About one-third of the world's rice area is in rain-fed lowlands and most are prone to water shortage. The identification of genes imparting tolerance to drought in the model cereal plant, rice, is an attractive strategy to engineer improved drought tolerance not only rice but other cereals as well. It is demonstrated that RNAi-mediated disruption of a rice farnesyltransferase/squalene synthase (SQS) by maize squalene synthase improves drought tolerance at both the vegetative and reproductive stages. Twenty-day-old seedlings of wild type (Nipponbare) and seven independent events of transgenic RNAi lines showed no difference in morphology. When subjected to water stress for a period of 32 d under growth chamber conditions, transgenic positives showed delayed wilting, conserved more soil water, and improved recovery. When five independent events along with wild-type plants were subjected to drought at the reproductive stage under greenhouse conditions, the transgenic plants lost water more slowly compared with the wild type, through reduced stomatal conductance and the retention of high leaf relative water content (RWC). After 28 d of slow progressive soil drying, transgenic plants recovered better and flowered earlier than wild-type plants. The yield of water-stressed transgenic positive plants ranged from 14-39% higher than wild-type plants. When grown in plates with Yoshida's nutrient solution with 1.2% agar, transgenic positives from three independent events showed increased root length and an enhanced number of lateral roots. The RNAi-mediated inactivation produced reduced stomatal conductance and subsequent drought tolerance.
Project description:Salt stress limits plant growth and agricultural productivity and plants have evolved suitable mechanisms to adapt to salinity environments. It is important to characterize genes involved in plant salt tolerance, which will advance our understanding of mechanisms mediating salt tolerance and help researchers design ways to improve crop performances under high salinity environments. Here, we reported a CYP450 family member, CYP75B4, improves salt tolerance of rice seedlings by inducing flavonoid tricin and cell wall lignin accumulation. The CYP75B4 is highly expressed in tissues rich in cell walls and induced by salt treatment. Subcellular localization analysis revealed that CYP75B4 is localized in the endoplasmic reticulum (ER). The CYP75B4 overexpressing (CYP75B4-OE) lines showed significant enhancement in stem mechanical strength, whereas the cyp75b4 null mutants displayed weaker stems, as compared to the wild-type. Notably, the cyp75b4 and CYP75B4-OE lines showed decreased and improved, respectively, salt tolerance performances in terms of survival rate, ROS accumulation, and Na+/ K+ homeostasis. Additionally, the cyp75b4 mutants had a decreased tricin level, whereas CYP75B4-OE lines showed an increased tricin content, under both control or salinity conditions. Furthermore, treating the cyp75b4 mutants with tricin partly resorted salt stress tolerance to the wild-type levels, indicating a role of CYP75B4-mediated tricin production in rice response to salinity. Consistently, another tricin-deficient mutant cyp93g1 also displayed salt sensitivity and the tricin application could partly restore its salt-sensitive phenotypes. Moreover, the CYP75B4 significantly promotes lignin deposition in cell walls of mature stems and seedlings under salinity conditions, which probably contributes to the enhanced stem mechanical strength and improved salt tolerance in CYP75B4-OE plants. Our findings reveal a novel function of CYP75B4 in rice salt tolerance and lodging resistance by inducing tricin accumulation and lignin deposition in cell walls.
Project description:BackgroundModerate salt stress, which often occurs in most saline agriculture land, suppresses crop growth and reduces crop yield. Rice, as an important food crop, is sensitive to salt stress and rice genotypes differ in their tolerance to salt stress. Despite extensive studies on salt tolerance of rice, a few studies have specifically investigated the mechanism by which rice plants respond and tolerate to moderate salt stress. Two rice genotypes differing in their tolerance to saline-alkaline stress, Dongdao-4 and Jigeng-88, were used to explore physiological and molecular mechanisms underlying tolerance to moderate salt stress.ResultsDongdao-4 plants displayed higher biomass, chlorophyll contents, and photosynthetic rates than Jigeng-88 under conditions of salt stress. No differences in K+ concentrations, Na+ concentrations and Na+/K+ ratio in shoots between Dongdao-4 and Jigeng-88 plants were detected when challenged by salt stress, suggesting that Na+ toxicity may not underpin the greater tolerance of Dongdao-4 to salt stress than that of Jigeng-88. We further demonstrated that Dongdao-4 plants had greater capacity to accumulate soluble sugars and proline (Pro) than Jigeng-88, thus conferring greater tolerance of Dongdao-4 to osmotic stress than Jigeng-88. Moreover, Dongdao-4 suffered from less oxidative stress than Jigeng-88 under salt stress due to higher activities of catalase (CAT) in Dongdao-4 seedlings. Finally, RNA-seq revealed that Dongdao-4 and Jigeng-88 differed in their gene expression in response to salt stress, such that salt stress changed expression of 456 and 740 genes in Dongdao-4 and Jigeng-88, respectively.ConclusionOur results revealed that Dongdao-4 plants were capable of tolerating to salt stress by enhanced accumulation of Pro and soluble sugars to tolerate osmotic stress, increasing the activities of CAT to minimize oxidative stress, while Na+ toxicity is not involved in the greater tolerance of Dongdao-4 to moderate salt stress.