苹果LEAFY同源基因的cDNA克隆与表达分析

 从苹果的果台枝顶芽中克隆了两个长约1.4 kb的cDNA片段，分别定名为AFL1和AFL2。它们的碱基序列在编码区有90%的同源性，但在3’末端非编码区仅有约印％的同源性。它们表达的肽链氨基酸序列与小叶杨、大豆、矮牵牛等有70％以上的同源性，与番茄、金鱼草、拟南芥有近70%的同源性，证明它们是LFY的同源基因。RT-PCR的结果表明，生长期AFL2在萼片、子房、根、茎、叶以及果台枝顶芽中都有表达，而AFL1只在果台枝顶芽中表达；在不同发育时期的果台枝顶芽中，AFL1在顶芽停止营养生长转向生殖生长以后才清晰表达，而AFL2在生长期6~10月都有表达。因此认为苹果中的这两个LFY同源基因虽有共同的起源，但是在功能上存在差异，在花和营养组织的发育中起不同的作用。DNA印迹分析表明，在苹果属及近缘的梨属植物中LFY同源基因是多拷贝的。

Cloning and Expression Analysis of LEAFY Homologues Genes from Apple

Two LEAFY like cDNA fragments of in length，AFL1 and AFL2 were cloned from the terminal buds of bearing shoot of apple trees．Sequencing analysis showed that the coding regions of AFL1 and AFL2 had 90% homolegy，but the 3’non-coding regions had less than 60% homology．The deduced amino acid sequence of AFL1 or AFL2 cDNA had over 70% similarity with PTFL ， PEAFLO and ALF genes of poplar、pea and petunia， and less than 70% similarity with TOFL， FLO and LFY genes of tomato， antirrhinum majus and arabidopsis respectivehy. RT-PCR analysis showed that AFL1 expressed only in the telminal buds during the transition period from vegetative to reproductive growth; whereas AFL2 expressed in the sepal, ovary, root, stem, leaf and the terminal buds between June to Oct. These results might suggest that AFL1 and AFL2 had a common origin， and their functions had diverged， so that they appeared to play independent roles inⅡ0Ial and vegetative tissue development．Southem blot analysis showed that there were at least two copies of LEAFY homo logues genes in Malus species and pear.