Expression differentiation of CYC-like floral symmetry genes correlated with their protein sequence divergence in Chirita heterotricha (Gesneriaceae)
Expression differentiation of CYC-like floral symmetry genes correlated with their protein sequence divergence in Chirita heterotricha (Gesneriaceae)
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苦苣苔科 CYC 样花对称基因的表达分化与其蛋白序列差异相关
DOI：
10.1007/s00427-008-0227-y
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发表时间：
2008-07-01
影响因子：
2.4
通讯作者：
Li, Zhen-Yu
中科院分区：
文献类型：
--
作者：
Gao, Qiu;Tao, Ju-Hong;Li, Zhen-Yu
CYCLOIDIEA（CYC）及其同源物已在模式生物金鱼草（Antirrhinum majus）和相关物种中进行了深入研究，研究它们在控制花的背腹（近轴-远轴）不对称性（包括使近轴和侧向雄蕊败育）方面的功能。这就提出了一个问题，是否同样的机制下的巨大的形态多样性的左右对称的被子植物，特别是在Lamiales广义宽，主要分支与左右对称的花。为了解决这个问题，我们选择了苦苣苔科的一个代表，苦苣苔目s.l.的其余部分的姐妹，分离CYC同源物，并使用位点特异性半定量逆转录酶聚合酶链反应进一步研究其表达模式。结果表明，异毛唇柱苣苔中4个CYC同源基因的表达存在时空差异，其中ChCYC 1D仅在近轴部位表达，ChCYC 1C的转录本在近轴和侧轴部位均有分布，而ChCYC 2A和ChCYC 2B的转录本仅在幼花序中表达。ChCYC 1C在侧生雄蕊中的表达与侧生雄蕊的败育有关。heterotricha暗示了它的功能增益，即，在表达上从近轴向侧部扩展。相关分析表明，ChCYC基因的蛋白质序列存在显著差异，其中GCYC 1和GCYC 2的保守功能域中存在一些谱系特异性氨基酸，GCYC 1C和GCYC 1D之间存在两个亚谱系特异性基序。我们的研究结果表明，ChCYC基因可能经历了一个表达分化和特化，在建立花背腹不对称的C。异毛藻在基因复制后对不同选择压力的反应。
CYCLOIDIEA (CYC) and its homologues have been studied intensively in the model organism Antirrhinum majus and related species regarding their function in controlling floral dorsoventral (adaxial-abaxial) asymmetry, including aborting the adaxial and lateral stamens. This raises the question whether the same mechanism underlies the great morphological diversity of zygomorphy in angiosperms, especially in Lamiales sensu lato, a major clade predominantly with zygomorphic flowers. To address this, we selected a representative in Gesneriaceae, the sister to the remainder of Lamiales s.l., to isolate CYC homologues and further investigate their expression patterns using locus-specific semiquantitative reverse transcriptase polymerase chain reaction. Our results showed that four CYC homologues in Chirita heterotricha differentiated spatially and temporally in expression, in which ChCYC1D was only expressed in the adaxial regions, and transcripts of ChCYC1C were distributed in both the adaxial and lateral regions, while ChCYC2A and ChCYC2B transcripts were only detected in the young inflorescences. ChCYC1C expression in the lateral regions correlated with abortion of the lateral stamens in C. heterotricha hinted at its gain of function, i.e., expanding from the adaxial to the lateral regions in expression. Correlatively, the protein sequences of ChCYC genes exhibited remarkable divergences, in which some lineage-specific amino acids between GCYC1 and GCYC2 in conserved functional domains and two sublineage-specific motifs between GCYC1C and GCYC1D in GCYC1 genes had further been identified. Our results indicated that ChCYC genes had probably undergone an expressional differentiation and specialization in establishing the floral dorsoventral asymmetry in C. heterotricha responding to different selective pressure after gene duplication.