Vandenbussche Michiel, Zethof Jan, Royaert Stefan, Weterings Koen, Gerats Tom
Department of Plant Systems Biology, Vlaams Instituut voor Biotechnologie/Ghent University, B-9052 Zwijnaarde, Belgium.
Plant Cell. 2004 Mar;16(3):741-54. doi: 10.1105/tpc.019166. Epub 2004 Feb 18.
In both Antirrhinum (Antirrhinum majus) and Arabidopsis (Arabidopsis thaliana), the floral B-function, which specifies petal and stamen development, is embedded in a heterodimer consisting of one DEFICIENS (DEF)/APETALA3 (AP3)-like and one GLOBOSA (GLO)/PISTILLATA (PI)-like MADS box protein. Here, we demonstrate that gene duplications in both the DEF/AP3 and GLO/PI lineages in Petunia hybrida (petunia) have led to a functional diversification of their respective members, which is reflected by partner specificity and whorl-specific functions among these proteins. Previously, it has been shown that mutations in PhDEF (formerly known as GREEN PETALS) only affect petal development. We have isolated insertion alleles for PhGLO1 (FLORAL BINDING PROTEIN1) and PhGLO2 (PETUNIA MADS BOX GENE2) and demonstrate unique and redundant properties of PhDEF, PhGLO1, and PhGLO2. Besides a full homeotic conversion of petals to sepals and of stamens to carpels as observed in phglo1 phglo2 and phdef phglo2 flowers, we found that gene dosage effects for several mutant combinations cause qualitative and quantitative changes in whorl 2 and 3 meristem fate, and we show that the PHDEF/PHGLO1 heterodimer controls the fusion of the stamen filaments with the petal tube. Nevertheless, when the activity of PhDEF, PhGLO1, and PhGLO2 are considered jointly, they basically appear to function as DEF/GLO does in Antirrhinum and to a lesser extent as AP3/PI in Arabidopsis. By contrast, our data suggest that the function of the fourth B-class MADS box member, the paleoAP3-type PETUNIA HYBRIDA TM6 (PhTM6) gene, differs significantly from the known euAP3-type DEF/AP3-like proteins; PhTM6 is mainly expressed in the developing stamens and ovary of wild-type flowers, whereas its expression level is upregulated in whorls 1 and 2 of an A-function floral mutant; PhTM6 is most likely not involved in petal development. The latter is consistent with the hypothesis that the evolutionary origin of the higher eudicot petal structure coincided with the appearance of the euAP3-type MADS box genes.
在金鱼草（金鱼草）和拟南芥（拟南芥）中，决定花瓣和雄蕊发育的花B功能，由一个DEFICIENS（DEF）/APETALA3（AP3）样和一个GLOBOSA（GLO）/PISTILLATA（PI）样MADS盒蛋白组成的异二聚体承担。在此，我们证明矮牵牛（矮牵牛）中DEF/AP3和GLO/PI谱系中的基因重复导致了其各自成员的功能多样化，这体现在这些蛋白之间的伴侣特异性和轮特异性功能上。此前已表明，PhDEF（以前称为绿色花瓣）中的突变仅影响花瓣发育。我们分离出了PhGLO1（花结合蛋白1）和PhGLO2（矮牵牛MADS盒基因2）的插入等位基因，并证明了PhDEF、PhGLO1和PhGLO2具有独特和冗余的特性。除了在phglo1 phglo2和phdef phglo2花中观察到花瓣完全同源转化为萼片、雄蕊完全同源转化为心皮外，我们发现几种突变组合的基因剂量效应会导致第2和第3轮分生组织命运发生质和量的变化，并且我们表明PHDEF/PHGLO1异二聚体控制雄蕊花丝与花瓣管的融合。然而，当综合考虑PhDEF、PhGLO1和PhGLO2的活性时，它们基本上似乎像金鱼草中的DEF/GLO一样发挥作用，在较小程度上像拟南芥中的AP3/PI一样发挥作用。相比之下，我们的数据表明，第四个B类MADS盒成员，即古AP3型矮牵牛TM6（PhTM6）基因的功能，与已知的真AP3型DEF/AP3样蛋白有显著差异；PhTM6主要在野生型花的发育中的雄蕊和子房表达，而其表达水平在A功能花突变体的第1和第2轮中上调；PhTM6很可能不参与花瓣发育。后者与高等真双子叶植物花瓣结构的进化起源与真AP3型MADS盒基因的出现相一致这一假设相符。
