Starch biosynthesis is crucial in determining rice quality during rice endosperm development. This study obtained a stable inheritable white-core endosperm mutant, h5, by treating the japonica rice variety Nipponbare with MNU (N-methyl-N-nitro-sourea). The mutated gene is an allele of OsAGPL2, which encodes the large subunit of ADP-glucose pyrophosphorylase (AGPase), a key and rate-limiting enzyme in the rice starch biosynthesis pathway. A G-C mutation in the third exon of OsAGPL2 led to impaired starch synthesis, significantly reduced amylose content (AC) and gel consistency (GC), and a marked decrease in AGPase activity. The haplotype analysis revealed that an SNP in the 3′UTR and two SNPs in the 5′UTR of OsAGPL2 were associated with significant differences in AC and GC among rice resources. These SNPs can be utilized to design molecular markers for breeding programs to improve rice quality. This study elucidates the impact of OsAGPL2 on the eating and cooking quality of rice. It identifies superior haplotypes, providing a theoretical foundation and molecular markers for accumulating minor-effect genes to enhance rice quality.

In addition to increasing grain yield, improving rice (Oryza sativa L.) quality has received increasing attention recently. The cooking and eating quality (CEQ) is an important indicator of rice quality. Chalkiness and floury endosperm have a significant impact on the CEQ of rice, resulting in noticeable changes. Due to the easily observable phenotype of floury endosperm, cloning single gene mutations that cause floury endosperm and indirectly evaluating changes in CEQs facilitates the exploration of minor genes controlling CEQ. In this study, a stable genetic allele variant of flo4, named flo4-7, was obtained through EMS mutagenesis. The flo4-7 allele variant carries the cyOsPPDKB mutation. flo4-7 showed a significant reduction in compound starch granules and a significant increase in single starch granules in endosperm cells, indicating the involvement of cyOsPPDKB in the synthesis of endosperm starch. Additionally, flo4-7 exhibited a significant decrease in gel consistency (GC) compared to the wild type. Through the analysis of GC data from 166 rice germplasm resources, a C-T variation in the 18th exon of cyOsPPDKB was found to be a crucial site, causing a significant difference in GC between indica and japonica rice. This locus can be used in the future to develop molecular markers for molecular marker-assisted breeding. This study provides a good research foundation for improving the CEQ of rice.

Pyruvate kinase (PK) is the terminal rate-limiting enzyme of glycolysis and occupies a central position in plant energy metabolism and carbon skeleton allocation. Plant PK isoenzymes comprise the cytosolic pyruvate kinase (PKc) and the plastidic pyruvate kinase (PKp), which differ markedly in gene origin, protein structure, subcellular localization, and physiological function, exhibiting independent evolutionary histories and functional diversification. Recent studies have revealed that PKc possesses dynamic subcellular distribution, allowing it to shuttle among the cytosol, mitochondria, and nucleus, where it participates in stress responses and epigenetic regulation through protein–protein interactions. PKp is localized to plastids and connects carbon metabolism with lipid biosynthesis and the methylerythritol phosphate (MEP) pathway by supplying pyruvate, thereby playing critical roles in seed development and oil accumulation. This review comprehensively summarizes recent advances in plant PKc and PKp concerning protein structure and subunit composition, tissue-specific expression, subcellular localization, protein interaction networks, activity regulation, and their effects on plant growth, development, and stress responses. In addition, phylogenetic tree, motif, and domain analyses of pyruvate kinase genes from Oryza sativa (rice), Glycine max (soybean), Gossypium hirsutum (cotton), Solanum tuberosum (potato), Arachis hypogaea (peanut), and Arabidopsis thaliana, as well as promoter cis-element analyses, are performed. This review aims to provide theoretical references for crop quality improvement and stress-resilient breeding.