Somatic embryogenesis receptor-like kinases (SERKs) play an essential role in plant response to pathogen infection. Here we identified three SERK genes (HvSERK1/2/3) from barley, and aimed to determine their implication in defense responses to barley powdery mildew (Bgh). Although HvSERK1/2/3 share the characteristic domains of the SERK family, only HvSERK2 was significantly induced in barley leaves during Bgh infection. The expression of HvSERK2 was rapidly induced by hydrogen peroxide (H₂O₂) treatment, but not by treatment with salicylic acid (SA), methyl jasmonate (MeJA), ethephon (ETH), or abscisic acid (ABA). Bioinformatics analysis of the cloned HvSERK2 promoter revealed that it contains several elements responsible for defense responses against pathogens. Promoter functional analysis showed that the HvSERK2 promoter was induced by Bgh and H₂O₂. Subcellular localization analysis of HvSERK2 indicated that it is mainly located on the plasma membrane. Transient overexpression of HvSERK2 in epidermal cells of the susceptible barley cultivar Hua 30 reduced the Bgh haustorium index from 58.6% to 43.2%. This study suggests that the HvSERK2 gene plays a positive role in the improvement of barley resistance to powdery mildew, and provides new insight into the function of SERK genes in the biotic stress response of plants.

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.