中文摘要：

Phytochrome 3（PHY3）是一种特殊的既能吸收红光／远红光又能吸收蓝光的嵌合光受体，一些隐花植物利用PHY3提高在弱光环境下的光敏感性。但是，有关植物嵌合光受体的序列信息极为匮乏。文章采用反向PCR法分离了蕨类植物毛柄短肠蕨红／蓝光嵌合光受体编码基因的全长序列。序列分析表明：该基因没有内含子，仅包含一个长度为4278bp的开放阅读框，与铁线蕨PHY3的核苷酸序列具有80％以上的一致性。该基因编码一个1425个氨基酸组成的蛋白质，预测分子量为157kDa，理论等电点（pI）为6129。结构分析表明，PHY3是由光敏色素和向光色素蛋白融合而成，其N端序列与光敏色素N端序列类似，包括PAS、GAF和PHY结构域，负责结合吸收红光／远红光的藻蓝胆素生色团；而C端与完整的向光色素类似，由2个LOV和1个Ser／Thr激酶结构域组成，可结合吸收蓝光／UV—A的生色团黄素单核苷酸FMN。

英文摘要：

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, GAE and PHY, whereas the C-terminal region possessed a nearly complete phototropin motif with two LOV and one STKc domains.