Identification, characterization, and expression analysis of calmodulin and calmodulin-like genes in grapevine (Vitis vinifera) reveal likely roles in stress responses

Calcium (Ca2+) is an ubiquitous key second messenger in plants, where it modulates many developmental and adaptive processes in response to various stimuli. Several proteins containing Ca2+ binding domain have been identified in plants, including calmodulin (CaM) and calmodulin-like (CML) proteins, which play critical roles in translating Ca2+ signals into proper cellular responses. In this work, a genome-wide analysis conducted in Vitis vinifera identified three CaM- and 62 CML-encoding genes. We assigned gene family nomenclature, analyzed gene structure, chromosomal location and gene duplication, as well as protein motif organization. The phylogenetic clustering revealed a total of eight subgroups, including one unique clade of VviCaMs distinct from VviCMLs. VviCaMs were found to contain four EF-hand motifs whereas VviCML proteins have one to five. Most of grapevine CML genes were intronless, while VviCaMs were intron rich. All the genes were well spread among the 19 grapevine chromosomes and displayed a high level of duplication. The expression profiling of VviCaM/VviCML genes revealed a broad expression pattern across all grape organs and tissues at various developmental stages, and a significant modulation in biotic stress-related responses. Our results highlight the complexity of CaM/CML protein family also in grapevine, supporting the versatile role of its different members in modulating cellular responses to various stimuli, in particular to biotic stresses. This work lays the foundation for further functional and structural studies on specific grapevine CaMs/CMLs in order to better understand the role of Ca2+-binding proteins in grapevine and to explore their potential for further biotechnological applications.