de Martino Gemma, Pan Irvin, Emmanuel Eyal, Levy Avraham, Irish Vivian F
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Conecticut 06520, USA.
Plant Cell. 2006 Aug;18(8):1833-45. doi: 10.1105/tpc.106.042978. Epub 2006 Jul 14.
The floral homeotic APETALA3 (AP3) gene in Arabidopsis thaliana encodes a MADS box transcription factor required for specifying petal and stamen identities. AP3 is a member of the euAP3 lineage, which arose by gene duplication coincident with radiation of the core eudicots. Although Arabidopsis lacks genes in the paralogous Tomato MADS box gene 6 (TM6) lineage, tomato (Solanum lycopersicum) possesses both euAP3 and TM6 genes, which have functionally diversified. A loss-of-function mutation in Tomato AP3 (TAP3) resulted in homeotic transformations of both petals and stamens, whereas RNA interference-induced reduction in TM6 function resulted in flowers with homeotic defects primarily in stamens. The functional differences between these genes can be ascribed partly to different expression domains. When overexpressed in an equivalent domain, both genes can partially rescue the tap3 mutant, indicating that relative levels as well as spatial patterns of expression contribute to functional differences. Our results also indicate that the two proteins have differing biochemical capabilities. Together, these results suggest that TM6 and TAP3 play qualitatively different roles in floral development; they also support the ideas that the ancestral role of AP3 lineage genes was in specifying stamen development and that duplication and divergence in the AP3 lineage allowed for the acquisition of a role in petal specification in the core eudicots.
拟南芥中的花同源异型基因APETALA3(AP3)编码一种MADS盒转录因子,该因子是确定花瓣和雄蕊特征所必需的。AP3是真AP3谱系的成员,该谱系通过与核心真双子叶植物辐射同时发生的基因复制而产生。尽管拟南芥在旁系同源的番茄MADS盒基因6(TM6)谱系中缺乏基因,但番茄(Solanum lycopersicum)同时拥有真AP3和TM6基因,它们在功能上已经多样化。番茄AP3(TAP3)的功能丧失突变导致花瓣和雄蕊均发生同源异型转变,而RNA干扰诱导的TM6功能降低导致主要在雄蕊上出现同源异型缺陷的花。这些基因之间的功能差异部分可归因于不同的表达结构域。当在等效结构域中过表达时,这两个基因都可以部分挽救tap3突变体,这表明表达的相对水平以及空间模式都有助于功能差异。我们的结果还表明这两种蛋白质具有不同的生化能力。总之,这些结果表明TM6和TAP3在花发育中发挥着质的不同的作用;它们还支持以下观点:AP3谱系基因的祖先作用是确定雄蕊发育,并且AP3谱系中的复制和分化使得在核心真双子叶植物中获得了在花瓣确定中的作用。