Auxin Response Regulators in Arabidopsis Embryogenesis

拟南芥基因组编码至少20个IAA蛋白，参与对植物激素生长素的反应。IAA蛋白共有四个保守结构域，其中结构域II赋予蛋白质不稳定性。结构域III与调节生长素应答靶基因的ARF转录因子相互作用。目前尚不清楚不同的IAA蛋白如何产生特定的作用。我们关注的是bodenlos （bdl）突变体，由于IAA12结构域II的氨基酸交换，它在早期胚胎发生中表现出特定的缺陷。相比之下，其他6个IAA基因的同源突变不会导致胚胎发生缺陷。这个项目的目的是分析什么决定了bdl表型的特异性。我们将在BDL顺式调控序列的控制下，在转基因拟南芥中表达其他具有BDL同源（bdlh）突变的IAA编码序列。如果这些转基因可以模仿bdl表型，发育基因调控将赋予特异性的作用。然而，如果这些转基因不能模仿bdl的表型特异性，则bdl的作用存在于其氨基酸序列中。在后一种情况下，我们将“交换”BDL和其他IAA蛋白的区域以确定特异性决定因子。BDL特异性结构域将用于分离酵母双杂交系统中的特定相互作用物，然后进行功能分析。

The Arabidopsis genome encodes at least 20 IAA proteins involved in response to the plant hormone auxin. IAA proteins share four conserved domains, with domain II conferring protein instability. Domain III interacts with ARF transcription factors that regulate auxin-responsive target genes. It is unknown how specific effects are brought about by different IAA proteins. We have focused on the bodenlos (bdl) mutant which displays specific defects in early embryogenesis, due to an amino acid exchange in domain II of IAA12. By contrast, homologous mutations in six other IAA genes do not lead to defects in embryogenesis. The aim of this project is to analyse what determines the specificity of the bdl phenotype. We will express other IAA coding sequences with bdl-homologous (bdlh) mutations under the control of the BDL cis-regulatory sequences in transgenic Arabidopsis plants. If these transgenes can mimic the bdl phenotype developmental gene regulation would confer specificity of action. If, however, these transgenes can not mimic the bdl phenotype specificity of BDL action resides in its amino acid sequence. In the latter case, we will "swap" regions of BDL and other IAA proteins to identify the specificity determinat(s). BDL specificity domain(s) will be used to isolate specific interactors in the yeast two-hybrid system, followed by functional analyses.