[Identification and expression profile analysis of rice CRF gene family]

Cytokinin response factors (CRFs), as unique transcription factors in plants, play crucial roles in regulating development, phytohormone signaling pathway, and stress responses. In this study, we identified nine CRF genes from the rice genome by conducting a BLAST analysis using the protein sequences of twelve Arabidopsis AtCRFs. These genes are located on seven different rice chromosomes. We conducted a comprehensive analysis of the conserved domains, physicochemical properties, secondary structures, and phylogenetic relationships of rice CRF proteins using various online tools and local software. Additionally, we analyzed the exon-intron structures and cis-acting elements of OsCRFs, and found an abundance of elements relevant to phytohormone response and stress response on the promoters of rice CRF genes. Spatial-temporal expression pattern analysis revealed that four of the OsCRFs were barely expressed in all tested samples, while the other five were highly expressed in the leaf, panicle, or seed of rice. Microarray data showed that OsCRF genes are regulated to varying degrees by abscisic acid, auxin, cytokinin, and jasmonic acid. Furthermore, through analyzing the RNA-seq data, we found that OsCRFs are primarily involved in plant response to temperature stress (chilling and heat), with several OsCRFs also implicated in drought response, while hardly any respond to salt stress. This study provides an important basis for the functional characterization of rice CRF family genes.