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.

The composition and distribution of storage substances in rice endosperm directly affect grain quality. A floury endosperm mutant, wcr (white-core rice), was identified, exhibiting a loose arrangement of starch granules with a floury opaque appearance in the inner layer of mature grains, resulting in reduced grain weight. The total starch and amylose content remained unchanged, but the levels of the four component proteins in the mutant brown rice significantly decreased. Additionally, the milled rice (inner endosperm) showed a significant decrease in total starch and amylose content, accompanied by a nearly threefold increase in albumin content. The swelling capacity of mutant starch was reduced, and its chain length distribution was altered. The target gene was mapped on chromosome 5 within a 65 kb region. A frameshift mutation occurred due to an insertion of an extra C base in the second exon of the cyOsPPDKB gene, which encodes pyruvate phosphate dikinase. Expression analysis revealed that wcr not only affected genes involved in starch metabolism but also downregulated expression levels of genes associated with storage protein synthesis. Overall, wcr plays a crucial role as a regulator factor influencing protein synthesis and starch metabolism in rice grains.

Grain chalkiness is an undesirable trait that significantly compromises rice quality, attracting considerable attention from both consumers and breeders. In this study, we characterized the role of the autophagy-related gene OsATG4b in rice grain development. OsATG4b was predominantly expressed in the endosperm. Compared with wild-type plants, OsATG4b-overexpressing lines exhibited significantly reduced grain chalkiness, whereas OsATG4b knockout mutants displayed a marked increase in chalkiness. Importantly, OsATG4b had no significant effect on other major agronomic traits. Ultrastructure analysis of the endosperm and evaluation of seed storage components revealed that the chalky endosperm in osatg4b mutants contained loosely packed starch granules, aberrant protein bodies, and reduced levels of seed storage proteins. Furthermore, gene expression analysis indicated that OsATG4b regulates the expression of genes involved in storage protein biosynthesis. Together, these findings demonstrate that OsATG4b plays a critical regulatory role in determining grain chalkiness in rice.

The Yangtze River Delta (YRD) is one of the most important japonica rice planting areas in China. Balancing the resistance, yield, and quality has always been a core issue in rice breeding due to the negative correlation among these three factors, while the broad-spectrum blast resistance gene Piz is closely linked with Hd1, the major gene regulating days to heading (DTH), and a precise combination of their beneficial alleles plays a key role in synchronously improving blast resistance and the regional adaptability of japonica rice in YRD. In this study, using the backcross progeny population derived from backbone parent ZD9471 and W1063, two alleles of Hd1 were identified. Then, through molecular marker-assisted selection combined with Green Super Rice 40K (GSR40K) chip-based screening, six introgression lines (ILs) with two different alleles combinations of Hd1 and Pigm were obtained. An evaluation of the blast resistance, yield, and quality traits showed that compared with the recipient parent, the panicle blast resistance of ILs was significantly enhanced; the grain number per panicle increased consistently with the delaying of the growth period, leading to higher yield in the ILs; the grain quality were synchronously improved. Two representative lines with similar genetic backgrounds but a significantly different regional adaptability, exhibiting a good blast resistance, high yield, and prominent quality were approved and demonstrated promising application prospects.

Grain chalkiness is an undesirable trait that significantly compromises rice quality, attracting considerable attention from both consumers and breeders. In this study, we characterized the role of the autophagy-related gene OsATG4b in rice grain development. OsATG4b was predominantly expressed in the endosperm. Compared with wild-type plants, OsATG4b-overexpressing lines exhibited significantly reduced grain chalkiness, whereas OsATG4b knockout mutants displayed a marked increase in chalkiness. Importantly, OsATG4b had no significant effect on other major agronomic traits. Ultrastructure analysis of the endosperm and evaluation of seed storage components revealed that the chalky endosperm in OsATG4b Knockout mutants contained loosely packed starch granules, aberrant protein bodies, and reduced levels of seed storage proteins. Furthermore, gene expression analysis indicated that OsATG4b regulates the expression of genes involved in storage protein biosynthesis. Together, these findings demonstrate that OsATG4b plays a critical regulatory role in determining grain chalkiness in rice.