In silico Studies on Crk Genes in Different Plant Species - Arabidopsis, Populus Etc

In plants, receptor-like protein kinases (RLKs) play essential roles in signal transduction by recognizing extracellular stimuli and activating the downstream signaling pathways. Cysteine-rich receptor-like kinases (CRKs) constitute a large subfamily of RLKs. They are distinguished by the presence of  DUF26 motifs enriched in cysteine residues in the extracellular domains, which act as potential targets for redox regulation. Microarray online data show a significant up-regulation of many CRKs genes under biotic and abiotic stimuli, suggesting that they might serve as sensors for reactive oxygen species. Bioinformatic studies identified more than 40 CRK members in the genomes of higher vascular plants, such as Arabidopsis thaliana, Populus trichocarpa, Oryza sativa and Sorghum bicolor. On the other hand, only six members of this family were found in a lycophyte species, Selaginella moellendorffii, and no CRK genes were identified in the early diverging bryophyte species, Physcomitrella patens, suggesting that CRK gene family has experienced a dramatic expansion especially in angiosperms. Many CRKs genes are located in tandem arrays and possess a high degree of structural similarity, indicating that they evolved as a result of gene duplication mechanisms. The analysis cis-regulatory elements in CRK gene promoters showed a large enrichment in W-Box motifs (TTGAC), which are recognized and bound specifically by WRKY transcription factors. It suggests that CRK kinases might regulate stress responses via salicylic acid-mediated signaling.