The heading date is one of the important traits in rice, which greatly affects grain yield and regional adaptability. Although the flowering pathways in rice have been extensively investigated, the genes involved in flowering remain largely unknown. Here, we report a rice lhd mutant, which showed late flowering under both long-day (LD) and short-day (SD) conditions. Through MutMap+ and linkage analysis, a deletion mutation in OsMetAP10 was inferred as the most likely candidate for lhd late flowering. OsMetAP10 encodes a methionine aminopeptidase that belongs to the peptidase_M24 subfamily III. The OsMetAP10 gene is constitutively expressed in rice and is induced by light, with a rhythmic expression pattern. OsMetAP10 knockout lines displayed late heading as the lhd mutation, while no alternations in morphology and heading were observed on OsMetAP10 overexpression lines, further confirming the mutation of OsMetAP10 as responsible for the late heading of lhd. Through RT-qPCR and transcriptome analysis, we revealed that the upregulated expression of the FT-like gene OsFLT4, a negatively flowering regulator, and the downregulation of flower development-related genes, OsMADS14, OsMADS15, and OsMADS34, played critical roles in determining the late flowering of the OsMetAP10 mutation. This study reports a new gene affecting flowering and provides a new insight into the role of OsMetAP10 in regulating rice heading.

This study elucidates the key molecular features underlying the embryogenic initiation divergence between japonica rice Chongxiangjing (CXJ) and indica rice 9311 during isolated microspore culture. Comparative transcriptome analysis across critical timepoints (0, 5, and 10 days post-culture initiation) revealed that while both varieties initially exhibit comparable microspore viability, CXJ maintains transcriptional stability and activates developmental programs (e.g., hormone signaling, DNA replication, cell morphogenesis), enabling sustained callus formation. In contrast, 9311 undergoes drastic transcriptome reorganization by 5 days, characterized by maladaptive activation of stress-response pathways (glutathione metabolism, MAPK signaling, ER stress) and futile metabolic reactivation (photosynthesis, starch degradation), culminating in near-total cell death and failed callus induction. Transcription factor dynamics further explain this divergence: CXJ specifically upregulates regulators coordinating development and stress resilience (NAC, ERF, HSF, GRAS, bZIP), while 9311 exhibits detrimental upregulation of FAR1 and B3, leading to catastrophic energy misallocation. These findings identify master transcriptional networks and stress-response pathways as pivotal indicators of embryogenic initiation efficiency, providing strategic targets for enhancing indica rice microspore culture technology.

Serine carboxypeptidase-like (SCPL) proteins play important roles in plant secondary metabolism, growth, and stress responses. Several SCPL members have been reported to participate in the biosynthesis of antimicrobial compounds associated with plant immunity. However, systematic characterization of the SCPL gene family in rice and its potential involvement in sheath blight (ShB) responses remains largely unclear. In this study, 45 SCPL genes were identified using the IRGSP-1.0 reference assembly and Ensembl Plants release 54 annotation and designated as OsSCPL1–OsSCPL45. Phylogenetic analysis of SCPL proteins from rice, Arabidopsis, soybean, and maize classified these proteins into three groups. Gene structures, conserved motifs, chromosomal distribution, and promoter cis-elements were subsequently analyzed. Chromosomal mapping and collinearity analysis revealed that both tandem and segmental duplications contributed to the expansion of the OsSCPL gene family. Promoter analysis identified numerous cis-elements associated with stress and hormone signaling. Mock-controlled RT-qPCR results of OsSCPL genes in resistant rice genotype YSBR1 and susceptible rice genotype Lemont (LE) showed that 14 OsSCPL genes were significantly up- or downregulated following Rhizoctonia solani inoculation in at least one genotype. The segmentally duplicated gene pair OsSCPL4 was significantly upregulated in both genotypes, whereas OsSCPL25 was significantly upregulated in YSBR1 but did not reach significance in LE. This study provides an updated genomic framework for the SCPL gene family in rice and suggests potential roles for OsSCPL4 and OsSCPL25 in rice responses to R. solani, laying a foundation for further functional studies.