Molecular characterisation and expression analysis of a novel calreticulin (CRT) gene in the dinoflagellate Prorocentrum minimum.

Calreticulin is a multifunctional Ca(2+)-binding protein that has been well characterised in mammalian cells. Here, we characterised a novel calreticulin (CRT2) gene in the dinoflagellate Prorocentrum minimum, which codes for a calcium binding protein and examined its expression pattern following the addition of calcium and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). PmCRT2 is encoded in the nuclear genome of P. minimum without introns. The full length cDNA of PmCRT2 was found to be 1,493 base pairs (bp) in length, which ranges from the dinoflagellate spliced leader sequence to the poly (A) tail and contains a 1,173-bp open reading frame, a 70-bp 5'-untranslated region (UTR), and a 207-bp 3'-UTR. On the basis of in silico analyses that revealed the distinct domain architectures of PmCRT2, we classified this protein under the calreticulin family. PmCRT2 gene expression was up-regulated in the presence of excess calcium in a dose-dependent manner; however, PmCRT2 expression was down-regulated by the addition of EGTA. These results clearly indicate that PmCRT2 plays a vital role in calcium regulation and this may be involved in the stress response of P. minimum.