苦苣苔科大叶石上莲CYC类基因RT-PCR表达模式研究

CYC类基因的分子系统学研究已经在苦苣苔科Gesneriaceae中展开,但是还缺乏对这些基因表达和功能的研究。因此,我们选择苦苣苔科大叶石上莲Oreocharis benthamii作为实验材料,分离出了CYC类基因的两个拷贝,经过分子系统学分析这两个基因分别属于苦苣苔科GCYC1和GCYC2两个分支,故命名为ObCYC1和ObCYC2。分区的RT-PCR实验结果显示这两个基因拥有不同的时间空间表达模式。ObCYC1与模式植物金鱼草Antirrhinum majus中的CYC基因类似,集中在花冠背部区域表达,这与它们拥有保守的功能区TCP和R相一致。但是,ObCYC1与CYC表达模式仍有区别,即,和CYC相比ObCYC1在花冠背部区域的表达提前减弱。这可能和大叶石上莲花冠微弱的两侧对称性相关。另外,由于大叶石上莲的背部花瓣较两侧和腹部花瓣小,因此,在功能上ObCYC1可能起抑制背部花瓣生长作用而CYC基因则促进背部花瓣生长。与ObCYC1不同,ObCYC2的保守功能区有更多的氨基酸位点变化,而且在RT-PCR实验中也没有检测到它的表达。因此,需要开展更深入的实验研究分析ObCYC2的基本功能,这将有助于了解GCYC2类基因在苦苣苔科及其近缘科中的功能和进化途径。

Significance of RT-PCR expression patterns of CYC-like genes in Oreocharis benthamii (Gesneriaceae)

We isolated and characterized two CYC-like genes from Oreocharis benthamii Clark (Gesneriaceae) in order to investigate their expression patterns. Phylogenetic analysis demonstrates that the two CYC-like genes, ObCYC1 and ObCYC2, belong to GCYC1 and GCYC2 clades in Gesneriaceae, respectively. Gene-specific RT-PCR results show that they have different spatio-temporal expression patterns. ObCYC1 is mainly expressed in the adaxial region of developing flowers as CYC is in Antirrhinum majus. The expression pattern of ObCYC1 demonstrates its basic function of controlling the adaxial floral organ development that is similar to that of CYC in Antirrhinum, which is in correlation with their conserved function domains, i.e. TCP and R domains. However, ObCYC1 is likely to repress the growth of both the adaxial petals and adaxial staminode. In addition, the weakened expression of ObCYC1 near flowering is correlated with the flower morphology of Oreocharis which is characteristic of weak zygomorphy. ObCYC2 exhibits a remarkable differentiation in protein sequence of TCP and R domain in comparison with those of ObCYC1 and CYC. Correlatively, ObCYC2 is inactive in floral tissue. This unique feature of ObCYC2 needs to be investigated by further comparative study both in expression and function in order to understand its basic function and evolutionary pathway in Gesneriaceae and related families.