Rice最新文献

Ghd7 is a central regulator to multiple growth and development processes in rice. While it is not clear how Ghd7 is regulated by upstream factors. To identify its upstream regulator, the truncated Ghd7 promoter fragments were used to screen cis elements binding to rice total nuclear proteins. Electrophoretic mobility shift assays screened one truncated fragment f3 binding to the proteins. Subsequently, the fragment f3 was employed to screen a yeast one-hybrid library, and a transcription factor OsIAA23 was screened as a direct upstream regulator of Ghd7. Dual-luciferase transient assay demonstrated the transcriptional repression effect of OsIAA23 on the activity of Ghd7, and the location of the cis elements binding to OsIAA23 in the region 1264 to 1255 bp upstream of ATG. Genetic analysis between the wild type Ghd7-OsIAA23 and single/double mutants further verified that OsIAA23 downregulated Ghd7 expression and led to a delayed heading under long day conditions. Moreover, natural variations in fragment f3 were associated with heading and geographic distribution in rice. This study sheds light on the direct regulatory mechanism of OsIAA23 on Ghd7, which enriches the understanding of the Ghd7 involved flowering regulatory network in rice.

The roles of plant-specific transcription factor family YABBY may vary among different members. OsYABBY6 is a rice YABBY gene, whose function is not well elucidated so far. In this paper, we show that OsYABBY6 is a nucleus-localized protein with transcriptional activation activity. OsYABBY6 is predominantly expressed in the palea and lemma, as well as in the sheath, culm and node. OsYABBY6 RNA interference (RNAi) plants exhibited altered plant height and larger grain size. Under cold treatment, OsYABBY6 overexpression (OE) plants had up-regulated expression of cold responsive genes, and accumulated less reactive oxygen species but more proline compared to wild type, resulting in improved cold tolerance. On the other hand, RNAi plants showed enhanced drought tolerance compared to the wild type by slower water loss, less reactive oxygen species but more proline and soluble sugar accumulation. In addition, endogenous abscisic acid (ABA) level was reduced in OsYABBY6 RNAi plants, and RNAi and OE plants were more and less sensitive to ABA treatment, respectively. Accordingly, we deduce that OsYABBY6 positively regulates cold response but negatively regulates drought response through different pathways. Our study reveals the crucial roles of OsYABBY6 in plant architecture and grain development, as well as in abiotic stress response, providing new insights into the functions of YABBYs in rice.

Phosphatidylinositol signaling system plays a crucial role in plant physiology and development, phosphatidylinositol phosphate kinases (PIPKs) are one of the essential enzymes responsible for catalyzing the synthesis of phosphatidylinositol bisphosphate (PIP2) within this signaling pathway. However, its mechanism of signal transduction remains poorly exploited in plants. OsMBL1, a jacalin-related mannose-binding lectin in rice, plays a crucial role in plant defense mechanisms, acting as a key component of the pattern-triggered immunity (PTI) pathway. Here, a rice phosphatidylinositol-phosphate kinase FAB (OsPIPK-FAB), a member of the rice PIPKs family, as an interacting protein of OsMBL1 through yeast-two-hybrid (Y2H) screening assay. And this interaction was confirmed by using co-immunoprecipitation (Co-IP) and pull-down assay techniques. Furthermore, we demonstrated that the deletion of OsPIPK-FAB gene in plant enhanced resistance against rice blast while overexpression of OsPIPK-FAB increases sensitivity to the fungal infection. Additionally, through determination and measurement of the plant inositol 1,4,5-trisphosphate (IP3) contents and the plant phosphatidylinositol 4-phosphate 5-kinase (PIP5K) activity, we revealed that OsMBL1 inhibits the PIP5K kinase activity of OsPIPK-FAB as well as the plant IP3 contents in rice. Conclusively, these findings indicated that OsPIPK-FAB serves as a novel and critical component that is negatively involved in PTI activation and was inhibited by OsMBL1.

The yield potential of large-panicle rice is often limited by grain-filling barriers caused by the development of inferior spikelets (IS). Photoassimilates, which are the main source of rice grain filling, mainly enter the caryopsis through the dorsal vascular bundle. The distribution of assimilates between superior spikelets (SS) and IS is influenced by auxin-mediated apical dominance; however, the mechanism involved is still unclear. In this study, the effect of auxin signaling on the grain filling of SS and IS was investigated in two large-panicle japonica rice varieties, W1844 and CJ03. Compared to SS, IS displayed delayed initiation of filling and a significantly lower grain weight. Furthermore, the endosperm development in IS remained stagnant at the coenocytic stage. The development of the dorsal vascular bundle in the IS was also slow, and poor sucrose-unloading was observed during the initial grain filling stage. However, the endosperm development in IS immediately started after the improvement of dorsal vascular bundle development. GUS activity staining further revealed that indole-3-acetic (IAA) was localized in the dorsal vascular bundle and surrounding areas, suggesting that the low IAA content observed in the IS during the initial grain filling stage may have delayed the development of the dorsal vascular bundle. Therefore, these results demonstrate that IAA may control sugar transport and unloading by regulating dorsal vascular bundle development, consequently affecting endosperm development in IS.

Clade A type 2C protein phosphatases (PP2Cs) are crucial components of the abscisic acid (ABA) signaling pathway. Research on clade A PP2Cs has focused more on their roles related to ABA signaling and stress responses than on the molecular mechanisms mediating their effects on plant growth and grain yield. Rice (Oryza sativa L.) is an important food crop worldwide. We previously determined that OsPP2C49, which encodes a rice clade A PP2C family member, negatively controls rice responses to drought, salt, and high-temperature stresses. In this study, we investigated the regulatory effects of OsPP2C49 on ABA responses and rice grain yield. By analyzing potential interactions with core ABA components, including pyrabactin resistance 1 (PYR1)/PYR1-like (PYL)/regulatory component of the ABA receptor (RCAR) and stress-activated protein kinases (SAPKs), we confirmed that OsPP2C49 is involved in the ABA signaling pathway. OsPP2C49 overexpression led to decreased ABA sensitivity and increased rice grain yield; the opposite phenotypes were observed in the ospp2c49 knockout mutants. Therefore, OsPP2C49 negatively regulates ABA responses, but positively modulates rice grain yield. Furthermore, we found that OsPP2C49 can interact with and dephosphorylate five OsSAPKs in vitro. Unlike OsPP2C49, these OsSAPKs positively modulate ABA responsiveness, but negatively affect rice yield. These findings indicate that OsPP2C49 may partially regulate ABA responses and rice grain production by dephosphorylating OsSAPKs. This study preliminarily explored the molecular basis of the regulatory effects of OsPP2C49 on rice plant growth and grain yield.

Plant tissue culture is extensively employed in plant functional genomics research and crop genetic improvement breeding. The callus induction ability is critical for utilizing Agrobacterium-mediated genetic transformation. In this study, we conducted a genome-wide association study (GWAS) utilizing 368 rice accessions to identify traits associated with callus induction rate (CIR), resulting in the identification of a total of 104 significant SNP loci. Integrated with gene function annotation and transcriptome analysis, 13 high-confidence candidate genes involved in auxin-related, CYC cyclins, and histone H3K9-specific methyltransferase were identified in significant loci. Furthermore, we also verified a candidate gene, Os05g0493500 (OsCycB1;5), and employed the CRISPR/Cas9 system to generate OsCycB1;5 knockout mutants in rice (Oryza sativa L.). The OscycB1;5 mutant displays significantly reduced callus induction and proliferation capacity, this result indicating OsCycB1;5 is required for the callus formation in rice. Overall, this study provides several reliable loci and high-confidence candidate genes that may significantly affect callus formation in rice. This information will offer valuable insights into the mechanisms underlying callus formation not only in rice but also in other plants.

Abiotic stress is one of the major factors restricting the production of rice (Oryza sativa L.). Developing rice varieties with dual abiotic stress tolerance is essential to ensure sustained rice production, which is necessary to illustrate the regulation mechanisms underlying dual stress tolerance. At present, only a few genes that regulate dual abiotic stress tolerance have been reported. In this study, we determined that the expression of OsMT2b was induced by both drought and Cd²⁺ stress. After stress treatment, OsMT2b-overexpression lines exhibited enhanced drought tolerance and better physiological performance in terms of relative water content and electrolyte leakage compared with wild-type (WT). Further analysis indicated that ROS levels were lower in OsMT2b-overexpression lines than in WT following stress treatment, suggesting that OsMT2b-overexpression lines had a stronger ability to scavenge ROS under stress. Reverse transcription-quantitative PCR (RT-qPCR) results demonstrated that under drought stress, OsMT2b influenced the expression of genes involved in ROS scavenging to enhance drought tolerance in rice. In addition, OsMT2b-overexpression plants displayed increased tolerance to Cd²⁺ stress, and physiological assessment results were consistent with the observed phenotypic improvements. Thus, enhancing ROS scavenging ability through OsMT2b overexpression is a novel strategy to boost rice tolerance to both drought and Cd²⁺ stress, offering a promising approach for developing rice germplasm with enhanced resistance to the abiotic stressors.

The rice, like other plants, undergoes photoprotection mode by increasing nonphotochemical quenching (NPQ) in high light intensity (> 1200 µmol m^− 2s^− 1 PPFD), which attenuates photosystem II yield (φPSII) drastically. The plant remains in photoprotection mode even after light intensity becomes not stressful for an extended period. While there are significant differences in the time it takes for photoprotection to recover among different genotypes, its use is limited in plant breeding because measuring the chlorophyll fluorescence parameters in progressive actinic light after dark adaptation takes more than forty-five minutes per genotype. The study finds that instantly measured A₄₀₀/A₁₈₀₀ ratio by five minutes in flag leaves of 25 diverse genotypes strongly associated with the φPSII₄₀₀ differences between theoretical and actual, qPd₄₀₀ and NPQ₄₀₀ with R² values 0.74, 0.65 and 0.60, respectively. In two consecutive years, GWAS of A₄₀₀/A₁₈₀₀ ratio identified the regions with genes reported earlier for plant photoprotection recovery. Additionally, QTL analysis in a RIL population also identified the regions carrying known genes related to photoprotection. Thus, the A₄₀₀/A₁₈₀₀ ratio can quickly phenotype many plants for easier introgression of the traits in popular cultivars. The identified genotypes, genes, and QTLs can be used to improve yield potential and allele mining.

The transcription factor WRKYs play pivotal roles in the adapting to adverse environments in plants. Prior research has demonstrated the involvement of OsWRKY70 in resistance against herbivores and its response to abiotic stress. Here, we reported the functional analysis of OsWRKY70 in immunity against fungal diseases and cold tolerance. The results revealed that OsWRKY70 was induced by various Magnaporthe oryzae strains. Knock out mutants of OsWRKY70, which were generated by the CRISPR/Cas9 system, exhibited enhanced resistance to M. oryzae. This was consistent with fortifying the reactive oxygen species (ROS) burst after inoculation in the mutants, elevated transcript levels of defense-responsive genes (OsPR1b, OsPBZ1, OsPOX8.1 and OsPOX22.3) and the observation of the sluggish growth of invasive hyphae under fluorescence microscope. RNA sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) validations demonstrated that differentially expressed genes were related to plant-pathogen interactions, hormone transduction and MAPK cascades. Notably, OsbHLH6, a key component of the JA signaling pathway, was down-regulated in the mutants compared to wild type plants. Further investigation confirmed that OsWRKY70 bound to the promoter of OsbHLH6 by semi-in vivo chromatin immunoprecipitation (ChIP). Additionally, the loss-function of OsWRKY70 impaired cold tolerance in rice. The enhanced susceptibility in the mutants characterized by excessive ROS production, elevated ion leakage rate and increased malondialdehyde content, as well as decreased activity of catalase (CAT) and peroxidase (POD) under low temperature stress was, which might be attributed to down-regulation of cold-responsive genes (OsLti6b and OsICE1). In conclusion, our findings indicate that OsWRKY70 negatively contributes to blast resistance but positively regulates cold tolerance in rice, providing a strategy for crop breeding with tolerance to stress.