毛柄短肠蕨红／蓝光嵌合光受体基因的克隆和蛋白质结构分析

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

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6.29。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。

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.