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The demand for rice grain quality, particularly in terms of eating and cooking quality, is increasingly concerning at present. However, the limited availability of rice-quality-related gene resources and time-consuming and inefficient traditional breeding methods have severely hindered the pace of rice grain quality improvement. Exploring novel methods for improving rice grain quality and creating new germplasms is an urgent problem that needs to be addressed. In this study, an amino-acid-transporter-encoding gene OsAAP11 (Os11g0195600) mainly expressed in endosperm was selected as the target for gene editing using the CRISPR/Cas9 system in three japonica genetic backgrounds (Wuyungeng30, Nangeng9108, and Yanggeng158, hereafter referred to as WYG30, NG9108, and YG158). We successfully obtained homozygous osaap11 mutants without transgenic insertion. Subsequently, we conducted comprehensive investigations on the agronomic traits, rice grain quality traits, and transcriptomic analysis of these mutants. The results demonstrate that loss of OsAAP11 function led to a reduced amino acid content and total protein content in grains without affecting the agronomic traits of the plants; meanwhile, it significantly increased the peak viscosity, holding viscosity, and final viscosity values during the cooking process, thereby enhancing the eating and cooking quality. This study not only provides valuable genetic resources and fundamental materials for improving rice grain quality but also provides novel technical support for the rapid enhancement of rice grain quality. [ABSTRACT FROM AUTHOR]

SUMMARY: Rice eating and cooking quality (ECQ) is a major concern of breeders and consumers, determining market competitiveness worldwide. Rice grain protein content (GPC) is negatively related to ECQ, making it possible to improve ECQ by manipulating GPC. However, GPC is genetically complex and sensitive to environmental conditions; therefore, little progress has been made in traditional breeding for ECQ. Here, we report that CRISPR/Cas9‐mediated knockout of genes encoding the grain storage protein glutelin rapidly produced lines with downregulated GPC and improved ECQ. Our finding provides a new strategy for improving rice ECQ. [ABSTRACT FROM AUTHOR]

Summary: Meiotic recombination is closely linked with homologous pairing and synapsis. Previous studies have shown that HOMOLOGOUS PAIRING PROTEIN2 (HOP2), plays an essential role in homologous pairing and synapsis. However, the mechanism by which HOP2 regulates crossover (CO) formation has not been elucidated. Here, we show that OsHOP2 mediates the maturation of COs by promoting homologous pairing and synapsis in rice (Oryza sativa) meiosis.We used a combination of genetic analysis, immunolocalization and super‐resolution imaging to analyze the function of OsHOP2 in rice meiosis.We showed that full‐length pairing, synapsis and CO formation are disturbed in Oshop2 meiocytes. Moreover, structured illumination microscopy showed that OsHOP2 localized to chromatin and displayed considerable co‐localization with axial elements (AEs) and central elements (CEs). Importantly, the interaction between OsHOP2 and a transverse filament protein of synaptonemal complex (ZEP1), provided further evidence that OsHOP2 was involved in assembly or stabilization of the structure of the synaptonemal complex (SC). Although the initiation of recombination and CO designation occur normally in Oshop2 mutants, mature COs were severely reduced, and human enhancer of invasion 10 (HEI10)10 foci were only present on the synapsed region.Putting the data together, we speculate that OsHOP2 may serve as a global regulator to coordinate homologous pairing, synapsis and meiotic recombination in rice meiosis. [ABSTRACT FROM AUTHOR]

Summary Panicle architecture is one of the most important agronomical traits that directly contribute to grain yield in rice ( Oryza sativa L.). We report herein an in-depth characterization of two allelic larger panicle ( lp) mutants that show significantly increased panicle size as well as improved plant architecture. Morphological analyses reveal that panicles of two mutants produced more inflorescence branches, especially the primary branches, and contained more grains. Moreover, mutant plants also display more lodging resistance than the wild type. The grain yield per plant in mutants is also increased, suggesting that mutant plants have useful potential for high grain yield in rice breeding. Map-based cloning reveals that LARGER PANICLE (LP) encodes a Kelch repeat-containing F-box protein. RNA in situ hybridization studies display that LP expression was enriched in the branch primordial region. Subcellular localization analyses demonstrate that LP is an endoplasmic reticulum (ER) localized protein, suggesting that LP might be involved in ER-associated protein degradation (ERAD). Using yeast two-hybrid assay and bimolecular fluorescence complementation analysis, we confirm that LP is an F-box protein and could interact with rice SKP1-like protein in an F-box domain-dependent manner. Quantitative real-time PCR results show that OsCKX2, which encodes cytokinin oxidase/dehydrogenase, is down-regulated evidently in mutants, implying that LP might be involved in modulating cytokinin level in plant tissues. These results suggest that LP plays an important role in regulating plant architecture, particularly in regulating panicle architecture, thereby representing promising targets for genetic improvement of grain production plants. [ABSTRACT FROM AUTHOR]

Rice seed size is an important agronomic trait in determining the yield potential, and four seed size related genes ( GS3, GW2, qSW5/ GW5 and GIF1) have been cloned in rice so far. However, the relationship among these four genes is still unclear, which will impede the process of gene pyramiding breeding program to some extent. To shade light on the relationship of above four genes, gene expression analysis was performed with GS3-RNAi, GW2-RNAi lines and CSSL of qSW5 at the transcriptional level. The results clearly showed that qSW5 and GW2 positively regulate the expression of GS3. Meanwhile, qSW5 can be down-regulated by repression of GW2 transcription. Additionally, GIF1 expression was found to be positively regulated by qSW5 but negatively by GW2 and GS3. Moreover, the allelic effects of qSW5 and GS3 were detailedly characterized based on a natural population consisting of 180 rice cultivars. It was indicated that mutual interactions exist between the two genes, in which, qSW5 affecting seed length is masked by GS3 alleles, and GS3 affecting seed width is masked by qSW5 alleles. These findings provide more insights into the molecular mechanisms underlying seed size development in rice and are likely to be useful for improving rice grain yield. [ABSTRACT FROM AUTHOR]

The semidwarf gene sd-g which has been used in indica rice breeding in southern China is a new one, nonallelic to sd-1. To map sd-g, an F2 population derived from the cross between Xinguiaishuangai and 02428 was constructed. The sd-g was roughly mapped between two microsatellite markers RM440 and RM163, with genetic distances of 0.5 and 2.5 cM, respectively. Then nine new polymorphic microsatellite markers were developed in this region. The sd-g was further mapped between two microsatellite markers SSR5-1 and SSR5-51, with genetic distances of 0.1 and 0.3 cM, respectively, while cosegregated with SSR418. A BAC contig was found to span the sd-g locus, the region being delimited to 85 kb. This result was very useful for cloning of the sd-g gene. [ABSTRACT FROM AUTHOR]