Acts as a calcium sensor. May promote vacuolation of aleurone cells in response to signal induced by gibberellin. CBL proteins interact with CIPK serine-threonine protein kinases. Binding of a CBL protein to the regulatory NAF domain of a CIPK protein lead to the activation of the kinase in a calcium-dependent manner (By similarity). Homodimer. Tonoplast. Expressed in roots, shoots, culms, young spikelets and scutellum. By gibberellin. Belongs to the calcineurin regulatory subunit family.