Molecular cloning and protein structure analyses of red/blue light chimeric photoreceptor from <I>Allantodia dilatata</I> (Bl.) Ching

Phytochrome 3 (PHY3) is a novel chimeric photoreceptor that can respond to both red/far red and blue light. Using this photoreceptor, some cryptogams could enhance light sensitivity under low light environment. But PHY3 sequence information is still extremely limited. In the present study, a full-length PHY3 genomic sequence was cloned from a fern Allantodia dilatata (Bl.) Ching by inverse PCR approaches. Sequence analysis showed that introns were absent in the gene. It contained a 4 278 bp open reading frame, encoding a deduced protein of 1 425 amino acid residues with a theoretical isoelectric point (pI) of 6.29 and a calculated molecular mass about 157 kDa. Protein domain search and structure analyses indicated that PHY3 originated from the recombination of two different photoreceptors. Its N-terminal section consisted of a putative functional phytochrome chromophore-binding domain including PAS, GAF, and PHY, whereas the C-terminal region possessed a nearly complete phototropin motif with two LOV and one STKc domains.