Griffiths Simon, Dunford Roy P, Coupland George, Laurie David A
John Innes Centre, Norwich Research Park, Colney, United Kingdom.
Plant Physiol. 2003 Apr;131(4):1855-67. doi: 10.1104/pp.102.016188.
The CO (CONSTANS) gene of Arabidopsis has an important role in the regulation of flowering by photoperiod. CO is part of a gene family with 17 members that are subdivided into three classes, termed Group I to III here. All members of the family have a CCT (CO, CO-like, TOC1) domain near the carboxy terminus. Group I genes, which include CO, have two zinc finger B-boxes near the amino terminus. Group II genes have one B-box, and Group III genes have one B-box and a second diverged zinc finger. Analysis of rice (Oryza sativa) genomic sequence identified 16 genes (OsA-OsP) that were also divided into these three groups, showing that their evolution predates monocot/dicot divergence. Eight Group I genes (HvCO1-HvCO8) were isolated from barley (Hordeum vulgare), of which two (HvCO1 and HvCO2) were highly CO like. HvCO3 and its rice counterpart (OsB) had one B-box that was distantly related to Group II genes and was probably derived by internal deletion of a two B-box Group I gene. Sequence homology and comparative mapping showed that HvCO1 was the counterpart of OsA (Hd1), a major determinant of photoperiod sensitivity in rice. Major genes determining photoperiod response have been mapped in barley and wheat (Triticum aestivum), but none corresponded to CO-like genes. Thus, selection for variation in photoperiod response has affected different genes in rice and temperate cereals. The peptides of HvCO1, HvCO2 (barley), and Hd1 (rice) show significant structural differences from CO, particularly amino acid changes that are predicted to abolish B-box2 function, suggesting an evolutionary trend toward a one-B-box structure in the most CO-like cereal genes.
拟南芥的CO（CONSTANS）基因在光周期调控开花过程中起着重要作用。CO是一个由17个成员组成的基因家族的一部分，该家族可细分为三类，这里称为I至III组。该家族的所有成员在羧基末端附近都有一个CCT（CO、CO样、TOC1）结构域。I组基因，包括CO，在氨基末端附近有两个锌指B-boxes。II组基因有一个B-box，III组基因有一个B-box和第二个不同的锌指。对水稻（Oryza sativa）基因组序列的分析鉴定出16个基因（OsA - OsP），它们也被分为这三组，表明它们的进化早于单子叶植物/双子叶植物的分化。从大麦（Hordeum vulgare）中分离出8个I组基因（HvCO1 - HvCO8），其中两个（HvCO1和HvCO2）与CO高度相似。HvCO3及其水稻对应基因（OsB）有一个与II组基因远缘相关的B-box，可能是由一个具有两个B-box的I组基因内部缺失而来。序列同源性和比较图谱显示，HvCO1是水稻光周期敏感性的主要决定因素OsA（Hd1）的对应基因。已在大麦和小麦（Triticum aestivum）中定位了决定光周期反应的主要基因，但没有一个与CO样基因相对应。因此，对光周期反应变异的选择影响了水稻和温带谷类作物中的不同基因。HvCO1、HvCO2（大麦）和Hd1（水稻）的肽与CO显示出显著的结构差异，特别是预测会消除B-box2功能的氨基酸变化，这表明在最类似CO的谷类基因中存在向单B-box结构进化的趋势。
