Impact of VaCCaMK gene overexpression and its splicing isoforms on cell growth and stilbene accumulation in Vitis amurensis Rupr

Calcium (Ca²⁺) functions as an essential intracellular second messenger in plants, mediating processes such as pathogen defence, stress adaptation and enzyme activation. Plants possess multiple families of calcium‑binding proteins, and among these, calcium/calmodulin‑dependent protein kinases (CCaMKs) remain among the least characterized. Also, their dual capacity to bind both Ca²⁺ and calmodulin makes them a subject of significant research interest. Usually, there is one CCaMK gene per plant genome, but when we cloned the full-length VaCCaMK cDNA sequence, we found several transcripts with missing exons, so it is possible that alternative splicing increases the overall diversity of CCaMK sequences. This study investigated the role of CCaMKs in Vitis amurensis Rupr. under abiotic stress conditions using grapevine cell cultures overexpressing the VaCCaMK1 gene and its alternatives VaCCaMK1- s1, -s2. Results demonstrated that VaCCaMK1 ‑overexpressing cultures did not exhibit increased tolerance to salt, osmotic, cold, or heat stress. Additionally, the content of secondary metabolites, as represented by stilbenes mainly produced by used grapevine cells, remained largely unchanged. However, a significant increase in both fresh and dry cell mass was observed compared with the control group: fresh biomass increased 1.1–1.7‑fold, and dry biomass 1.1–1.8‑fold. These findings indicate that VaCCaMK genes do not affect plant cell susceptibility to the tested abiotic stresses. VaCCaMK1-s1 or - s2 the overexpression had a similar but weaker effect on grape cells. Nevertheless, VaCCaMK appear to act as a positive regulator of cell growth and development in V. amurensis , suggesting their potential role in enhancing biomass accumulation.