香蕉MuMA DS2的克隆、序列分析和表达分析

Isolation and Expression Characterization of a MADS-box Gene from Banana

根据抑制缩减文库获得的一个MADS-box基因片段,从香蕉果实cDNA文库中,采用RT-PCR技术分离获得一个全长cDNA,经序列测定和同源性分析表明,该cDNA含705bp的完整的开放阅读框,编码234个氨基酸残基的MADS-box蛋白,将其命名为MuMADS2。MuMADS2具有植物MADS-box基因家族中特有的M、I、K和C四个结构域,与芦笋、风信子、蝴蝶兰和百合的MADS-box基因的氨基酸序列存在很高的一致性(82%、78%、77%和75%)。将MuMADS2与其它植物来源的MADS-box基因进行序列比较发现,MuMADS2属于MADS-box基因的AGAMOUS亚族的D世系。RT-PCR分析表明,MuMADS2仅在生殖器官(花和果)中表达,在营养器官(根、茎和叶)中不表达。进一步分析发现MuMADS2仅在雄花和雌花的子房、由雌花发育而成的果实中表达,而在雄花和和雌花的柱头和花柱都不表达。推测MuMADS2可能在果实的发育和成熟过程中起作用。

On the base of the sequence from a differentially expressed clone encodes an MADS-box protein, a full-length cDNA is isolated from a banana fruit cDNA library by RT-PCR approach. It is sequenced that contains a 705 bp opening reading frame and encodes 234 amino acid resides. It is designated as MuMADS2, a kind of MADS-box gene. Sequence analysis indicates that the deduced amino acid sequence of MuMADS2 contains four typical conserve domains, M, I, K and C, which are usually specific in plants. MuMADS2 shared high identities of 82%, 78%, 77% and 75% to those of MADS-box protein from Asparagus virgatus, Hyacinthus orientalis, Phalaenopsis hybrid cultivar and Lilium longiflorum. Sequence comparison shows that MuMADS2 belongs to the AGAMOUS subfamily. Furthermore, phylogenetic analysis suggests that MuMADS2 is most likely a class D MADS-box gene. Reverse transcriptase-polymerase chain reaction （RT-PCR） analysis shows that MuMADS2 is expressed in the reproductive organs like flowers and fruits, whereas no expression is detected in the vegetative organs like root, stem and leaf. In detail MuMADS2 is only expressed in the ovary of male and female flower, the fruit developed from female flower, but not expressed in style/stigma of male and female flower. These results suggest that MuMADS2 may play an important role in banana fruit development and ripening.