CYC类基因属于植物特异的TCP转录因子，最早在模式植物金鱼草（Antirrhinum majus）中发现，与其同源基因DICHOTOMA (DICH) 通过在第二轮花器官上激活 RAD和抑制DIV基因以及在第三轮花器官上抑制 AmCYCLIN D3b基因而共同决定金鱼草花的背部属性，促进两侧对称性的建成。研究发现，核心真双子叶植物（core eudicots）中CYC类基因分为三个分支：CYC1、CYC2和CYC3，它们的功能在各类群中具有广泛保守性。其中CYC2具有决定花两侧对称性（背腹分化）的功能。菊科植物头状花序中的舌状花/假舌状花（以下均简称舌状花）是较极端的两侧对称花，可能是适应动物传粉的结果，近年来的研究表明，舌状花的形态建成也是CYC2类基因调控的结果。舌状花的有无在整个菊科植物的系统发育中反复出现，这种模式同样出现在春黄菊族内部，因此，该族是研究花对称性式样与植物之适应的理想类群。本研究选取春黄菊族蒿亚族中边缘花对称性不同的三个近缘属植物，甘菊、蓍状亚菊和百花蒿，利用基因组DNA测序和3’RACE方法分离得到了12个CYC类基因，分别归属核心真双子叶植物中CYC类基因的全部三个分支：CYC1（2个拷贝）、CYC2（8个拷贝）和CYC3（2个拷贝）。通过它们的氨基酸序列分析和进化树重建，发现CYC类基因拷贝数在不同物种间不同，各基因拷贝在序列上存在明显差异：甘菊、蓍状亚菊基因数和基因间同源关系完全相同，而百花蒿则缺乏CYC2c和CYC2a-3；比较RACE和基因组扩增测序的结果发现，除CYC3分支外，CYC1和CYC2支的基因在终止密码子附近均存在一个内含子结构；与其他拷贝相比，CYC2a序列变异较大，从基因组中一共分离得到三种类型，分别命名为CYC2a-1、CYC2a-2和CYC2a-3，并发现其中有内含子的选择性剪切；CYC2a-1在三个物种中均无表达；CYC2a-3在内含子之后的序列中存在两个poly A结构。通过RT-PCR方法研究了CYC类基因各拷贝在三种植物不同发育时期花序中的表达情况，发现：CYC类基因多数拷贝从花序发育早期开始表达并持续到开花阶段，但少数基因表达模式出现一定程度的分化；CYC2a的各拷贝显示多种表达式样，可能与其本身基因复杂性有关；CYC2f只在甘菊和蓍状亚菊中表达，而在百花蒿中没有检测到它的表达；以跨越内含子的引物扩增的RT-PCR检测到CYC1b在甘菊和蓍状亚菊中的表达结果出现两条扩增产物片段，说明其存在内含子选择性剪切。而CYC2c只表达于边缘舌状花而在管状花中 无表达。综上所述，在甘菊、蓍状亚菊和百花蒿中均发现的CYC类基因12个成员（百花蒿缺CYC2c和CYC2a-3）各自属于直系同源的基因谱系。CYC类基因的拷贝数目、核苷酸序列和表达模式在三个物种间存在一定的差异。

Shifts in flower symmetry have occurred frequently during the diversification of angiosperms, and such shifts may have played important roles in plant–pollinator interactions. Floral asymmetry is thought to have arisen for many times in the Flowering Plants independently from a radially symmetrical ancestral condition. Nowadays, the molecular changes underlying this innovation are found.CYCLOIDEA (CYC) gene was firstly found in Antirrhinum majus, and it was proved to be a key transcription factor to controlling floral symmetry. The function of its homologs (CYC-like genes) in other angiosperm taxa have been verified conservative. Functions of CYC-like genes to characterize dorsal or lateral organs (the whorl of petals and stamens) mainly depend on their specific and continuous expressing in the flower organs. In A. majus, RAD ang DIV genes, both belonging to the family of the MYB transcription factor, are found as downstream effectors of CYCLOIDEA gene in the petal. CYCLOIDEA and its downstream gene AmCYCLIN D3b make the dorsal stamen aborted.Inflorescence of the family Composite is characterized by capitulum comprising numerous florets. In radiate species, the outer florets (ray florets, zygomorphy) have large attractive petals, whereas the inner florets (disc florets, actinomorphy) tend to be less conspicuous. Loss of the radiate condition has occurred multiple times within Composite, yielding nonradiate species with only disc florets (the discoid flower head). Molecular mechanism of absence or presence of ray florets in the Composite plants was testified to correlate with CYC2 clade genes from studies on the Senecio species, Gerbera hybrida and Helianthus annuus. Up to five CYC2 clade members were found from these studies, which show higher copy number of the CYC2 clade than in other families of the core eudicots. However, it is unclear how these genes affect floral morphological development and to what an extent evolution of these genes has resulted in flower morphological divergence among closely related organisms.Here we address this problem by comparing CYC-like genes in three allies closely related but different in the type of capitula in the Artemisiinae (Anthemideae, Asteraceae). They are Chrysanthemum lavandulifolium with bilateral ray florets, i.e., with the radiate capitulum; Stilpnolepis centiflora with radial disc florets only, i.e., the discoid capitulum and Ajania achilleoides with a bilaterally disc-like florets (an intermediated morphology) around and disc florets inside, i.e., the disciform capitulum. By genomic DNA sequencing and 3’RACE technologies, we obtained 12 different sequence types, tentatively regared as 12 CYC-like gene copies. Phylogenetic analyses based on their DNA and amino acid sequences show that these copies fall into three groups corresponding to three major copies of the CYC-like gene family, CYC1 (2 copies), CYC2 (8 copies) and CYC3 (2 copies). The ancester of CYC2e and CYC2f found in the three studied speices is probably an ortholog of the GhCYC2 from Gerbra hybrida. Form the genomic DNA, three subcopies of CYC2a were isolated and sequenced from both Chrysanthemum lavandulifolium and Ajania achilleoides, named CYC2a-1, CYC2a-2 and CYC2a-3, but only CYC2a-1, CYC2a-2 were found in Stilpnolepis centiflora. Nevertheless, CYC2a-1 seems not expressing in all the three studied plants. Two indels characterized by two polyA regions after the intron result in the main divergence between CYC2a-1/CYC2a-2 and CYC2a-3. In addition, Stipnolepis centiflora, which has the discoid capitulum, is lack of CYC2c and CYC2a-3 copies comparing to the other two species.Gene-specific RT-PCR demonstrates that the 12 CYC-like copies have more or less different patterns of temporal expression. Most of them express in all three species in all flower development stages, wherease, CYC2f only expresses in Ajania achilleoides, and CYC2c only in a few developmental stages Of Chrysanthemum lavandulifoliumm and A. achilleoides. When blooming, CYC2c only expresses in ray rather than disc florets in C. lavandulifoliumm. The results of this study imply that changes in duplication numbers and expression patterns of the CYC-like genes may lead to the varation of floral symmetry in the phylogenetically closely related Chrysanthemum lavandulifolium, Ajania achilleoides and Stilpnolepis centiflora.