Abstract
Calcium-dependent protein kinases (CDPKs) are molecular switches that bind Ca2+, ATP, and protein substrates, acting as sensor relays and responders that convert Ca2+ signals, created by developmental processes and environmental stresses, into phosphorylation events. The precise functions of the CDPKs in grapevine (Vitis vinifera) are largely unknown. We therefore investigated the phylogenetic relationships and expression profiles of the 17 CDPK genes identified in the 12x grapevine genome sequence, resolving them into four subfamilies based on phylogenetic tree topology and gene structures. The origins of the CDPKs during grapevine evolution were characterized, involving 13 expansion events. Transcriptomic analysis using 54 tissues and developmental stages revealed three types of CDPK gene expression profiles: constitutive (housekeeping CDPKs), partitioned functions, and prevalent in pollen/stamen. We identified two duplicated CDPK genes that had evolved from housekeeping to pollen-prevalent functions and whose origin correlated with that of seed plants, suggesting neofunctionalization with an important role in pollen development and also potential value in the breeding of seedless varieties. We also found that CDPKs were involved in three abiotic stress signaling pathways and could therefore be used to investigate the crosstalk between stress responses.
Highlights
Protein kinases are molecular switches and signal responders that regulate plant growth and development, as well as biotic and abiotic stress responses [1]
Evolution of the grapevine calcium-dependent protein kinases (CDPKs) gene family The grapevine genome contains 17 VvCPK genes which are divided into four subfamilies, as previously reported in A. thaliana, rice, and as we showed in moss (Physcomitrella patens) and the spike moss (Selaginella moellendorffii) by a phylogenetic analysis (Figure S3)
The extant VvCPKs resulted from 13 expansions during the last 1 billion years based on the division of the four subfamilies into 12 sub-subfamilies according to the tree topology and gene structure, which will help to investigate expansions in other species including model organisms
Summary
Protein kinases are molecular switches and signal responders that regulate plant growth and development, as well as biotic and abiotic stress responses [1]. There are nearly 1000 protein kinases in Arabidopsis thaliana, accounting for ,4% of the proteome [1]. These include 34 calcium-dependent protein kinases (CDPKs), which can sense Ca2+ and convert developmental and environmental signals into phosphorylation events. CDPKs comprise four functional domains: an N-terminal variable domain (ND), a serine/threonine kinase domain (STKD), an auto-inhibitory junction domain (AID) and a regulatory calmodulin-like domain (CaM-LD). The AID, which may sometimes be part of the CaM-LD [5], contains a pseudo-substrate sequence that can interact with the active site and inhibit kinase activity. The CaMLD, which contains four EF-hands, can bind four calcium ions through interactions with eight alpha-helices [5]
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