Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2.
New Phytol. 2012 Apr;194(2):391-401. doi: 10.1111/j.1469-8137.2012.04064.x. Epub 2012 Feb 9.
Combinatorial interactions of AUXIN RESPONSE FACTORs (ARFs) and auxin/indole acetic acid (Aux/IAA) proteins through their common domains III and IV regulate auxin responses, but insight into the functions of individual proteins is still limited. As a new tool to explore this regulatory network, we generated a gain-of-function ARF genotype by eliminating domains III and IV from the functionally well-characterized ARF MONOPTEROS(MP)/ARF5. This truncated version of MP, termed MPΔ, conferred complementing MP activity, but also displayed a number of semi-dominant traits affecting auxin signaling and organ patterning. In MPΔ, the expression levels of many auxin-inducible genes, as well as rooting properties and vascular tissue abundance, were enhanced. Lateral organs were narrow, pointed and filled with parallel veins. This effect was epistatic over the vascular hypotrophy imposed by certain Aux/IAA mutations. Further, in MPΔ leaves, failure to turn off the procambium-selecting gene PIN1 led to the early establishment of oversized central procambial domains and very limited subsequent lateral growth of the leaf lamina. We conclude that MPΔ can selectively uncouple a single ARF from regulation by Aux/IAA proteins and can be used as a genetic tool to probe auxin pathways and explore leaf development.
通过其共同的结构域 III 和 IV，生长素反应因子（ARFs）和生长素/吲哚乙酸（Aux/IAA）蛋白的组合相互作用调节生长素反应，但对个别蛋白质功能的了解仍然有限。作为探索这个调控网络的新工具，我们通过从功能良好表征的 ARF 单脚类动物（MP）/ARF5 中去除结构域 III 和 IV 来产生功能获得性 ARF 基因型。这种被称为 MPΔ的 MP 截断版本赋予了互补的 MP 活性，但也表现出许多半显性特征，影响生长素信号和器官模式形成。在 MPΔ中，许多生长素诱导基因的表达水平，以及生根特性和血管组织丰度都得到了增强。侧生器官狭窄、尖锐且充满平行叶脉。这种效应在某些 Aux/IAA 突变引起的血管萎缩上是上位的。此外，在 MPΔ叶片中，未能关闭选择前韧皮部的基因 PIN1 导致过大的中央前韧皮部区域的早期建立和叶片薄片的后续侧向生长非常有限。我们得出结论，MPΔ可以选择性地将单个 ARF 从 Aux/IAA 蛋白的调控中分离出来，并可作为遗传工具用于探测生长素途径和探索叶片发育。
