Project description:Grain chalkiness is a complex trait adversely affecting appearance and milling quality, and therefore has been one of principal targets for rice improvement. Eliminating chalkiness from rice has been a daunting task due to the complex interaction between genotype and environment and the lack of molecular markers. In addition, the molecular mechanisms underlying grain chalkiness formation are still imperfectly understood. We identified a notched-belly mutant (DY1102) with high percentage of white-belly, which only occurs in the bottom part proximal to the embryo. Using this mutant, a novel comparison system that can minimize the effect of genetic background and growing environment was developed. An iTRAQ-based comparative display of the proteins between the bottom chalky part and the upper translucent part of grains of DY1102 was performed. A total of 113 proteins responsible for chalkiness formation was identified. Among them, 70 proteins are up-regulated and 43 down-regulated. Approximately half of these differentially expressed proteins involved in central metabolic or regulatory pathways including carbohydrate metabolism (especially cell wall synthesis) and protein synthesis, folding and degradation, providing proteomic confirmation of the notion that chalkiness formation involves diverse but delicately regulated pathways. Protein metabolism was the most abundant category, accounting for 27.4% of the total differentially expressed proteins. In addition, down regulation of PDIL 2-3 and BiP was detected in the chalky tissue, indicating the important role of protein metabolism in grain chalkiness formation. Using this novel comparison system, our comprehensive survey of endosperm proteomics in the notched-belly mutant provides a valuable proteomic resource for the characterization of pathways contributing to chalkiness formation at molecular and biochemical levels.
Project description:RNA-dependent RNA polymerase 6 (RDR6) is a core component of the small RNA biogenesis pathway, but its function in meiosis is unclear. Herein we report a new allele of OsRDR6 (Osrdr6-mei), which causes meiosis-specific phenotype in rice. In Osrdr6-mei, meiotic DSB formation was blocked to some extent. We further created a biallelic mutant, Osrdr6-bi, by crossing Osrdr6-mei with a knock out mutant, Osrdr6-edit (Osrdr6-edi). In Osrdr6-bi, 24 univalents were observed at diakinesis, and no histone H2AX phosphorylation (γH2AX) foci was detected in meiocytes, indicating that OsRDR6 is crucial for meiotic DSB formation. Compared with the wild type, the number of 21-nt small RNAs was dramatically reduced, while the number of 24-nt small RNAs was significantly increased in Osrdr6-mei. And thousands of DMRs discovered in Osrdr6-mei, implying that OsRDR6 plays an essential role on DNA methylation, especially CHH methylation. Meanwhile, the transcriptome data showed that 457 genes were down-regulated in the mutant; including three genes related to DSB formation: OsSDS, P31comet and CRC1. Interestingly, the increased 24-nt small RNA level surrounding down-regulated genes was largely associated with the silencing of these genes, while DMRs were rarely related to them. In summary, we speculated that the small RNA levels are disordered in Osrdr6 mutants, which may lead to the defection of DSB formation.
Project description:The profiling was conducted with the Rice 3'-Tiling 135k Microarray designed from 31,439 genes deposited at IRGSP, RAP2 database (http://rapdb.lab.nig.ac.jp). We have identified and characterized a T-DNA insert rice mutant (Osfuct) with loss of α1,3-fucosyltransferase function. Matrix-assisted laser desorption/ionization time-of-flight analyses of the N-glycan revealed the lack of α1,3-fucose in the N-glycan structure of rice Osfuct mutant. The mutant displayed the pleiotropic developmental defects such as diminished growth, shorter plant height, less number of tillers, shorter panicle lengths and internode, impaired anther and pollen development. In addition, the anther was curved, pollen grains shapes were shriveled, pollen viability and pollen number per anther was dramatically decreased in Osfuct mutant. The complementation test of Osfuct mutant clearly exhibited that the phenotype is caused by the loss of α1,3-fucosyltransferase function bescause complementation line is rescued. Transcriptome profiling data revealed that several genes essential in plant developmental processes were significantly altered in Osfuct mutant including protein kinases, transcription factors, genes involved in metabolism, genes related to protein synthesis and hypothetical proteins. Moreover, Osfuct mutant exhibited the enhanced salt insensitivity. Taken together, these findings demonstrated that Osfuct plays a critical role in growth, anther, pollen development and salt stress response.