Cryptochrome nucleocytoplasmic distribution and gene expression are regulated by light quality in the fern Adiantum capillus-veneris

Numerous cellular responses are reportedly regulated by blue light in gamet ophytes of lower plants; however, the molecular mechanisms of these respons es are not known. Here, we report the isolation of two blue light photorece ptor genes, designated cryptochrome genes 4 and 5 (CRY4 and CRY5), from the fern Adiantum capillus-veneris. Because previously we identified three cry ptochrome genes, this fern cryptochrome gene family of five members is the largest identified to date in plants. The deduced amino acid sequences of t he five genes show remarkable similarities with previously identified crypt ochromes as well as class I photolyases. Like the other plant cryptochromes , none of the cryptochromes of this fern possesses photolyase activity. RNA gel blot analysis and competitive polymerase chain reaction analysis indic ate that the expression of the newly identified CRY4 and CRY5 genes is regu lated by light and is under phytochrome control. The intracellular distribu tion of reporter beta-glucuronidase (GUS)-CRY fusion proteins indicates tha t GUS-CRY3 and GUS-CRY4 localize in fern gametophyte nuclei. The nuclear lo calization of GUS-CRY3 is regulated in a light-dependent manner. Together w ith our physiological knowledge, these results suggest that CRY3, CRY4, or both might be the photoreceptor that mediates inhibition of spore germinati on by blue light.