A Novel Calmodulin-like Protein Gene in Rice Which Has an Unusual Prolonged C-terminal Sequence Carrying a Putative Prenylation Site

A rice cDNA encoding a novel calmodulin-like protein was identified. It has 38 additional amino acids at the C-terminus of a complete, typical calmodulin (CaM) sequence of 149 amino acids. The four C-terminal amino acid residues form a CAAL motif which could be a site for protein prenylation and may subsequently cause the protein to become membrane associated. RT-PCR analysis confirmed that such a combined protein gene truly exists in rice. Sequence analysis of its genomic counterpart showed that there is an intron located at junction of the normal CaM sequence and the 38 C-terminal amino acids. This introduces a potential stop codon for normal CaM if an alternative splicing mechanism is involved. Southern blot analysis of rice genomic DNA revealed that there is only one locus for this gene. The northern blot analysis showed that this gene is highly expressed in rice roots, shoots and flowers. The distribution of this protein demonstrates the functional importance of this novel CaM-like protein in rice.