Insight into the CBL and CIPK Gene Families in Pecan (Carya illinoinensis): Identification, Evolution and Expression Patterns in Drought Response

Calcium Ca2 serves as a ubiquitous second messenger and plays a pivotal role in signal transduction Calcineurin B-like proteins CBLs are plant-specific Ca2sensors that interact with CBLinteracting protein kinases CIPKs to transmit Ca2 signals CBLCIPK complexes have been reported to play pivotal roles in plant development and response to drought stress however limited information is available about the CBL and CIPK genes in pecan an important nut crop In the present study a total of 9 CBL and 30 CIPK genes were identified from the pecan genome and divided into four and five clades based on phylogeny respectively Gene structure and distribution of conserved sequence motif analysis suggested that family members in the same clade commonly exhibited similar exonintron structures and motif compositions The segmental duplication events contributed largely to the expansion of pecan CBL and CIPK gene families and KaKs values revealed that all of them experienced strong negative selection Phylogenetic analysis of CIPK proteins from 14 plant species revealed that CIPKs in the intron-poor clade originated in seed plants Tissue-specific expression profiles of CiCBLs and CiCIPKs were analysed, presenting functional diversity Expression profiles derived from RNASeq revealed distinct expression patterns of CiCBLs and CiCIPKs under drought treatment in pecan Moreover coexpression network analysis helped to elucidate the relationships between these genes and identify potential candidates for the regulation of drought response which were verified by qRTPCR analysis Our study provides a basis for further functional analysis of CiCBLs and CiCIPKs in the drought stress response of pecan