Identification and Functional Analysis of KH Family Genes Associated with Salt Stress in Rice

Salinity stress has a great impact on crop growth and productivity and is one of the major factors responsible for crop yield losses. The K-homologous (KH) family proteins play vital roles in regulating plant development and responding to abiotic stress in plants. However, the systematic characterization of the KH family in rice is still lacking. In this study, we performed genome-wide identification and functional analysis of KH family genes and identified a total of 31 KH genes in rice. According to the homologs of KH genes in Arabidopsis thaliana, we constructed a phylogenetic tree with 61 KH genes containing 31 KH genes in Oryza sativa and 30 KH genes in Arabidopsis thaliana and separated them into three major groups. In silico tissue expression analysis showed that the OsKH genes are constitutively expressed. The qRT-PCR results revealed that eight OsKH genes responded strongly to salt stresses, and OsKH12 exhibited the strongest decrease in expression level, which was selected for further study. We generated the Oskh12-knockout mutant via the CRISPR/Cas9 genome-editing method. Further stress treatment and biochemical assays confirmed that Oskh12 mutant was more salt-sensitive than Nip and the expression of several key salt-tolerant genes in Oskh12 was significantly reduced. Taken together, our results shed light on the understanding of the KH family and provide a theoretical basis for future abiotic stress studies in rice.