In Arabidopsis, the protein DWF1 plays an enzymatic role in the biosynthesis of brassinosteroids, steroid hormones in plants that are required for growth. An interaction occurs between CaM and DWF1, and DWF1 being unable to bind CaM is unable to produce a regular growth phenotype in plants. Hence, CaM is essential for the DWF1 function in plant growth.
CaM binding proteins are also known to regulate reproductive development in plants. For instance, the CaM-binding protein kinase in tobacco acts as a negative regulator of flowering. However, these CaM-binding protein kinase are also present in the shoot apical meristem of tobacco and a high concentration of these kinases in the meristem causes a delayed transition to flowering in the plant.
S-locus receptor kinase (SRK) is another protein kinase that interacts with CaM. SRK is involved in the self-incompatibility responses involved in pollen-pistil interactions in Brassica.
CaM targets in Arabidopsis are also involved in pollen development and fertilization. Ca transporters are essential for pollen tube growth. Hence, a constant Ca gradient is maintained at the apex of pollen tube for elongation during the process of fertilization. Similarly, CaM is also essential at the pollen tube apex, where its primarily role involves the guidance of the pollen tube growth.