Genomic survey and expression analysis of the CDPK genes in Liriodendron Chinense to explore their potential functions under multiple abiotic stresses

Calcium-dependent protein kinases (CDPKs) are key components of calcium signal transduction pathway, which play crucial roles in plant growth, development and abiotic stress response. The forest tree Liriodendron chinense possesses high ecological, ornamental, and economic value; however, abiotic stresses restrict its growth, reproductive capacity, and geographical distribution. The identification of the CDPK gene family in L. chinense, along with analyses of their structural and evolutionary relationships, tissue-specific expression patterns, will facilitate the elucidation of their functions in responding to abiotic stresses. A total of 21 CDPK genes were identified in the L. chinense genome and phylogenetically classified into four distinct groups. Amino acid sequences of most CDPKs contained four typical EF-hand structures. The cis-acting elements analysis of the promoter region showed a general representation of the ARE, MBS and LTR elements related to abiotic stress. RNA-seq analysis revealed that 6 h, 24 h, and 3 d post-abiotic stress were critical time points for the plant’s regulatory responses. RT-qPCR expression profiles demonstrated that the selected LcCDPKs exhibited differential expression across various tissues, and expression profiling suggested a collective trend of responsiveness to these stresses, with the most pronounced and sustained transcriptional changes often observed under heat stress, followed by cold and then drought. Subcellular localization assays indicated that LcCDPK5-GFP and LcCDPK10-GFP were localized to the nucleus and cell membrane, while LcCDPK5 was additionally localized to the cytoplasm. This study systematically identified CDPKs in L. chinense, and indicates their potential roles in response to abiotic stress. This study provides important insights into the evolution and function of CDPKs in L. chinense.