Yu D, Kotilainen M, Pöllänen E, Mehto M, Elomaa P, Helariutta Y, Albert V A, Teeri T H
Institute of Biotechnology, University of Helsinki, Finland.
Plant J. 1999 Jan;17(1):51-62. doi: 10.1046/j.1365-313x.1999.00351.x.
We have used Gerbera hybrida (the cultivated ornamental, gerera) to investigate the molecular basis of flower development in Asteraceae, a family of flowering plants that have heteromorphic flowers and specialized floral organs. Flowers of the same genotype may differ in a number of parameters, including sex expression, symmetry, sympetaly and pigmentation. In order to study the role of organ identity determination in these phenomena we isolated and functionally analysed six MADS box genes from gerbera; these were shown by phylogenetic analysis to be orthologous to well characterized regulatory genes described from Arabidopsis and Antirrhinum. Expression analysis suggests that the two gerbera agamous orthologues, the globosa orthologue and one of the deficiens orthologues may have functional equivalency to their counterparts, participating in the C and B functions, respectively. However, the function of a second deficiens orthologue appears unrelated to the B function, and that of a squamosa orthologue seems distinct from squamosa as well as from the A function. The induction patterns of gerbera MADS box genes conform spatiotemporally to the multi-flowered, head-like inflorescence typical of Asteraceae. Furthermore, gerbera plants transgenic for the newly isolated MADS box genes shed light onto the mechanistic basis for some floral characteristics that are typical for Asteraceae. We can conclude, therefore, that the pappus bristles are sepals highly modified for seed dispersal, and that organ abortion in the female marginal flowers is dependent upon organ identity and not organ position when position is homeotically altered.
我们利用杂种非洲菊（一种人工栽培的观赏植物，即非洲菊）来研究菊科植物花发育的分子基础，菊科是一类具有异形花和特化花器官的开花植物家族。相同基因型的花在许多参数上可能存在差异，包括性别表达、对称性、花瓣联合和色素沉着。为了研究器官特征决定在这些现象中的作用，我们从非洲菊中分离并对六个MADS盒基因进行了功能分析；系统发育分析表明，这些基因与拟南芥和金鱼草中已明确的调控基因直系同源。表达分析表明，两个非洲菊无花瓣同源基因、globosa同源基因和一个deficiens同源基因可能分别与其对应基因具有功能等效性，参与C功能和B功能。然而，第二个deficiens同源基因的功能似乎与B功能无关，而一个squamosa同源基因的功能似乎既不同于squamosa，也不同于A功能。非洲菊MADS盒基因的诱导模式在时空上符合菊科典型的多花、头状花序。此外，转新分离MADS盒基因的非洲菊植株揭示了菊科一些典型花特征的机制基础。因此，我们可以得出结论，冠毛刚毛是为种子传播而高度特化的萼片，并且当位置发生同源异形改变时，雌性边缘花中的器官败育取决于器官特征而非器官位置。
