摘要
As AGAMOUS (AG) homologs are involved in determining the identity of sex organs, we have isolated an AG honolog from sex organs of cucumber by using RT-PCR. This gene was designated as CMBI. Southern analysis indicated that CMBI was present as a single-copy sequence in me genome of cucumber. Northern bybridizatiou demonstrated that CMBI mRNA accumulated in the stamens and pistils at anthesis of both male and female nowers, and mRNA levels in the stamens was much higher than that in the pistils. CMBI mRNA was not detected in the floral organ suck as petals, nor in vegetative organs which include stems and leaves. Furthermore, no signal was detect6d in the young aborted pistiles, suggesting that the activity of CMBI may be required for the normal pistils development in the male flowers.
黄瓜花发育的早期均有雌蕊必雄蕊原基的分化，但在发育过程中，由于雌蕊或雄蕊怕发育受到阻滞，导致雄花和雌花的形成。近年来在拟南芥和金鱼草等中遗传学的研究表明，花器官的特征是由同源异形基因决定的。在拟南芥中，由于AG在决定雄蕊和雌蕊特征方面起重要作用，本研究利用RT－PCR技术，从黄瓜的雌、雄蕊中分离出AG的同源基因，并在其花发育过程中的表达和可能作用进行了分析。首先，根据AG同源基因的保守区域设计5′简并引物5′－GA（A／G）AT（T／C。A）AA（G／A）（A。C）G（G。T／C）ATCGA（C／A）AAC－3′，然后进行3′RACE PCR，扩增出约1kb大小的片段。序列分析表明该片段含有非常保守的MADS box。进而，利用5′RACEPCR得到全长度的cDNA。该cDNA的核苷酸序列的CUMI（黄瓜MADSbox gene1)同源性高达97％。CUM1在矮牵牛中过量表达可引起花萼变为心皮状和花瓣变为雄蕊，说明CUM1为AG的同源基因，基于该基因与CUM1登记号为AF286649。Southern分子杂交结果显示，CMB1为单拷贝基因（Fig.2)。Northern分子杂交结果显示出，在茎、叶以及花瓣中，未检测到该基因的mRNA（Fig.3)，但在雄花的雄蕊和雌花的雌蕊中均有其mRNA的积累，而在雌蕊中mRNA（Fig.3)，但在雄花的雄和雌花的雌蕊中均有其mRNA的积累，而在雌中mRNA的水平显著代于雄蕊（Fig.3.4&5)，尤其是在雄花的滞育雌蕊中无该基因mRNA的积累（Fig.4)，推测CMB1对于雄花中雌蕊的正常发育可能是必需的。
基金
Supported by the National Natural Science Foundation of China! (No.39770358).
