Characterization of the Calmodulin/Calmodulin-like Protein (CAM/CML) Family in Ginkgo biloba, and the Influence of an Ectopically Expressed GbCML Gene (Gb_30819) on Seedling and Fruit Development of Transgenic Arabidopsis

Calmodulins (CAMs) and calmodulin-like proteins (CMLs) can participate in the regulation of various physiological processes via sensing and decoding Ca2+ signals. To reveal the characteristics of the CAM/CML family in Ginkgo biloba, a comprehensive analysis was performed at the genome-wide level. A total of 26 CAMs/CMLs, consisting of 5 GbCAMs and 21 GbCMLs, was identified on 11 out of 12 chromosomes in G. biloba. They displayed a certain degree of multiplicity in their sequences, albeit with conserved EF hands. Collinearity analysis suggested that tandem rather than segmental or whole-genome duplications were likely to play roles in the evolution of the Ginkgo CAM/CML family. Furthermore, GbCAMs/GbCMLs were grouped into higher, lower, and moderate expression in magnitude. The cis-acting regulatory elements involved in phytohormone-responsiveness within GbCAM/GbCML promotors may explain their varied expression profiles. The ectopic expression of a GbCML gene (Gb_30819) in transgenic Arabidopsis led to phenotypes with significantly shortened root length and seedling height, and decreased yields of both pods and seeds. Moreover, an electrophoresis mobility shift assay demonstrated the Ca2+-binding activity of Gb_30819 in vitro. Altogether, these results contribute to insights into the characteristics of the evolution and expression of GbCAMs/GbCMLs, as well as evidence for Ca2+-CAM/CML pathways functioning within the ancient gymnosperm G. biloba.