Genome-Wide Identification of Serine carboxypeptidase-like (SCPL) Genes in Rice and Their Expression in Response to Rhizoctonia solani

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.