Genome-wide identification of CrRLK1L gene family and desiccation-induced expression profiles in Boea hygrometrica

Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) proteins constitute a subfamily of receptor-like kinases (RLKs) that play diverse roles during fertilization, vegetative development and plant pathogen interactions. CrRLK1Ls possess a unique malectin-like domain at N-terminal that bind to oligo-or polysaccharides from cell wall polymers, byproducts of cell wall degradation, or membrane-associated or secreted glycosylated proteins. CrRLK1L members have been identified in many organisms, however, the study of this gene family in resur-rection plant species has not been reported to date. Resurrection plants are a kind of extremophiles that can survive extreme drought stress (desiccation) and recover rapidly after rehydration, and display specific and reversible cell wall structure and component changes during dehydration and rehydration. Here, we identified 18 CrRLK1L protein members in the resurrection plant Boea hygrometrica genome and classified them into 9 clades based on the conserved amino acid sequences. Phylogenetic analysis reveals the expansion of FER clade, the absence of MEDOS and CVY clades and the emergence of a new Bh-specific clade in BhCrRLK1L protein family. Analysis of cis-regulatory elements has predicted several types of drought induced elements and/or drought related hormone responsiveness elements in the promoter regions of all BhCrRLK1Ls. In agreement, we found 15 members of BhCrRLK1Ls change their expression pattern in response to drought stress, based on a previous transcriptome survey. Subsequent qRT-PCR validation of selected 7 BhCrRLK1L genes confirmed that BhFER1, BhCrRLK1L14 and BhCrRLK1L15 are induced by desiccation, and BhFER3, BhCrRLK1L17 and BhCrRLK1L18 are repressed by desiccation. Our study systematically identified the CrRLK1L members in B. hygrometrica, and analyzed the gene expression profiles in response to desiccation stresses, which lays a foundation for exploring the function of BhCrRLK1Ls in desiccation signal transduction in B. hygrometrica.