A Genome-Wide Characterization of Receptor-like Cytoplasmic Kinase IV Subfamily Members in Identifies the Potential Role of in Plant Osmotic Stress Responses.

The IV subfamily of receptor-like cytoplasmic kinase (RLCK-IV), known as calcium-binding receptor-like cytoplasmic kinases (CRCKs), plays a vital role in plant signal transduction, particularly in coordinating growth and responses to abiotic stresses. However, our comprehension of CRCK genes in , a species characterized as fast-growing and pest-resistant but with drought intolerance, is limited. Here, we identify 6 members of the CRCK subfamily on a genome-wide scale in , denoted as -. An evolutionary and structural analysis revealed highly conserved kinase catalytic domains across all PdeCRCKs, characterized by calmodulin (CaM)-binding sites and serine (Ser)/threonine (Thr) phosphorylation sites. The -acting elements of promoters indicated the presence of responsive elements for plant hormones, abiotic stresses, and transcription factor binding sites, which is supported by the distinct transcriptional expression patterns of under abscisic acid (ABA), polyethylene glycol (PEG), and mannitol treatments. A transient overexpression of in tobacco () leaves indicated their involvement in reactive oxygen species (ROS) scavenging, polyamine gene synthesis, and ABA signaling pathway modulation. Immunoprecipitation-Mass Spectrometry (IP-MS) and a yeast two-hybrid (Y2H) assay showed that PdeCRCK6 interacted with AAA-type ATPase proteins and ubiquitin, suggesting its potential function in being involved in chloroplast homeostasis and the 26S ubiquitin protease system. Taken together, these findings offer a comprehensive analysis of the RLCK-IV subfamily members in , especially laying a foundation for revealing the potential mechanism of in response to osmotic stresses and accelerating the molecular design breeding of drought tolerance in poplar.