Halfter U, Ali N, Stockhaus J, Ren L, Chua N H
Laboratory of Plant Molecular Biology, Rockefeller University, New York, NY 10021.
EMBO J. 1994 Mar 15;13(6):1443-9. doi: 10.1002/j.1460-2075.1994.tb06398.x.
Genetic studies in Arabidopsis and Antirrhinum showed that petal determination requires the concomitant expression of two homeotic functions, A and B, whereas the A function alone determines sepal identity. The B function is represented by at least two genes. The Petunia homeotic gene green petal (gp) is essential for petal determination as demonstrated by a Petunia gp mutant that has sepals instead of petals. We have used ectopic expression of the gp gene as a tool to study flower development in Petunia. CaMV 35S-gp expression leads to homeotic conversion of sepals into petaloid organs when expressed early in development. This demonstrates that a single homeotic gene is sufficient to induce homeotic conversion of sepals to petals, suggesting that other petal determining genes are regulated in part by ectopically expressed gp. Indeed, two other MADS-box-containing genes, pmads 2 and fbp 1, which show homology to the Antirrhinum B function gene globosa, are activated in the converted petal tissue. Furthermore, our data provide evidence for autoregulation of gp expression in the petaloid tissue and uncover the role of gp in fusion of petal tissues.
拟南芥和金鱼草的遗传学研究表明，花瓣的决定需要两种同源异型功能A和B同时表达，而单独的A功能决定萼片的特征。B功能由至少两个基因代表。矮牵牛同源异型基因绿色花瓣（gp）对于花瓣的决定至关重要，这一点在一个具有萼片而非花瓣的矮牵牛gp突变体中得到了证明。我们利用gp基因的异位表达作为工具来研究矮牵牛的花发育。CaMV 35S-gp在发育早期表达时会导致萼片向花瓣状器官的同源异型转变。这表明单个同源异型基因足以诱导萼片向花瓣的同源异型转变，这意味着其他决定花瓣的基因部分受异位表达的gp调控。事实上，另外两个含MADS盒的基因pmads 2和fbp 1，它们与金鱼草的B功能基因globosa具有同源性，在转化的花瓣组织中被激活。此外，我们的数据为gp在花瓣状组织中的自调控提供了证据，并揭示了gp在花瓣组织融合中的作用。
