香蕉乙烯受体基因cDNA的克隆及其表达分析

提取香蕉果实总RNA，根据有关文献报道的乙烯受体基因序列设计引物，通过RT-PCR方法扩增其开放读框(open reading frame，ORF)，结果同时扩增出2个长短不同的特异cDNA序列。测序结果表明：其中较长的cDNA序列与该报道的香蕉乙烯受体cDNA序列的对应区段(ORF)长度一致，同源性为99．1％；另一较短cDNA序列为新序列，其与该报道序列的同源性达97．2％，但缺少该报道序列中的19和1036 bp的区段。RT-PCR扩增结果显示，报道的cDNA序列在香蕉果实的几个成熟阶段均有表达，而在根和叶片等组织中检测不到其表达，说明其表达具有果实组织特异性。Southern杂交结果显示，该报道基因序列在香蕉基因组中为单拷贝存在。因此，推测新克隆的缺失cDNA序列可能来自同一基因的转录后剪辑，其可能为1个新的香蕉乙烯受体基因。

Cloning and Expression Analysis of Ethylene Receptor Gene in Banana Fruit

Using total RNA from banana fruits as template, two different lengths of cDNA fragments were specifically amplified by RT-PCR, which revealed significant homology to the reported ethylene receptor gene (Gene bank number: AF113748). One cDNA clone (the longer one) shows 99 % of homology to the ORF(open reading frame)sequence of the ethylene receptor gene, while the shorter cDNA clone displayed 97 % identity but with a missing region corresponding to nucleotide 194 to 1 036. Analyses of expression profile by RT-PCR of the cloned genes demonstrated that its expression was prominent at different developmental stages of ripening banana fruit. In contrast, their expression in the roots and leaves was non-detectable. The result of southern hybridization showed that this gene sequence existed as a single copy in the banana genomic DNA. The results indicated a fruit tissue-specific expression pattern of the cloned ethylene receptor cDNA. The truncated form ethylene receptor cDNA was likely generated through alternative splicing, and therefore might represent a novel form of ethylene receptor gene in banana.