Positive selection and expression divergence following gene duplication in the sunflower CYCLOIDEA gene family
Positive selection and expression divergence following gene duplication in the sunflower CYCLOIDEA gene family
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DOI：
10.1093/molbev/msn001
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发表时间：
2008-07-01
影响因子：
10.7
通讯作者：
Burke, John M.
中科院分区：
文献类型：
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作者：
Chapman, Mark A.;Leebens-Mack, James H.;Burke, John M.
Cycloidae(CyC)/teosinte-BRANCHED1(TB1)转录因子家族的成员参与了金鱼草和莲花的左右对称花的进化和玉米驯化过程中分枝表型的丧失。向日葵(Heliantus annuus L.Asteraceae)的复合花序同时含有左右对称和辐射对称(即径向对称)的小花，栽培的向日葵由于其高度分枝的野生祖先的驯化而进化出不分枝的表型；因此，与CyC/Tb1相关的基因在这个研究系统中引起了极大的兴趣。我们在向日葵中鉴定了10个CyC/TB1基因家族成员，这是迄今为止在任何被研究的物种中发现的最多的成员。系统发育分析表明，这些基因存在于3个不同的分支中，这与之前在其他优树物种中的研究一致。复制事件的年代测定和连锁作图的组合表明，只有部分复制与多倍化有关。CyC类基因和分枝相关的数量性状基因座之间的共分离表明，这些基因在分枝过程中发挥的作用很小，如果有的话。然而，一个基因的表达模式表明，在射线小花与花盘小花的发育中可能起到了作用。分子进化分析表明，在基因复制后，保守区域中的残基是正选择的目标。综上所述，这些结果表明基因复制和功能分化在向日葵细胞色素C基因家族的多样性中发挥了重要作用。
Members of the CYCLOIDEA(CYC)/TEOSINTE-BRANCHED1 (TB1) group of transcription factors have been implicated in the evolution of zygomorphic (i.e., bilaterally symmetric) flowers in Antirrhinum and Lotus and the loss of branching phenotype during the domestication of maize. The composite inflorescences of sunflower (Helianthus annuus L. Asteraceae) contain both zygomorphic and actinomorphic (i.e., radially symmetric) florets (rays and disks, respectively), and the cultivated sunflower has evolved an unbranched phenotype in response to domestication from its highly branched wild progenitor; hence, genes related to CYC/TB1 are of great interest in this study system. We identified 10 members of the CYC/TB1 gene family in sunflower, which is more than found in any other species investigated to date. Phylogenetic analysis indicates that these genes occur in 3 distinct clades, consistent with previous research in other eudicot species. A combination of dating the duplication events and linkage mapping indicates that only some of the duplications were associated with polyploidization. Cosegregation between CYC-like genes and branching-related quantitative trait loci suggest a minor, if any, role for these genes in conferring differences in branching. However, the expression patterns of one gene suggest a possible role in the development of ray versus disk florets. Molecular evolutionary analyses reveal that residues in the conserved domains were the targets of positive selection following gene duplication. Taken together, these results indicate that gene duplication and functional divergence have played a major role in diversification of the sunflower CYC gene family.