Members of a novel class of Arabidopsis Rho guanine nucleotide exchange factors control rho GTPase-dependent polar growth
Members of a novel class of Arabidopsis Rho guanine nucleotide exchange factors control rho GTPase-dependent polar growth
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DOI：
10.1105/tpc.105.036434
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发表时间：
2006-02-01
期刊：
影响因子：
11.6
通讯作者：
Yang, ZB
中科院分区：
文献类型：
--
作者：
Gu, Y;Li, SD;Yang, ZB
Rho家族小GTP酶是控制许多真核细胞过程的信号开关。从GDP到GTP结合形式的转化由鸟嘌呤核苷酸交换因子（GEF）催化。动物中的Rho GEF分为两种结构不同的类别，含有DH和DOCKER催化结构域。在酵母双杂交筛选中，我们使用植物Rho GTfl（ROP 1）作为诱饵，鉴定了Rho GEFs家族，命名为RopGEFs。拟南芥RopGEF家族的14个成员包含一个保守的中央结构域，未知功能的结构域315（DUF 315），和可变的N-和C-末端区域。体外GEF测定显示DUF 315而不是RopGEF 1的全长版本对ROP 1具有高GEF活性。我们的数据表明，RopGEF 1的可变区参与调节RopGEF通过自抑制机制。RopGEF 1在花粉管中的过表达产生生长去极化，组成型活性ROP 1突变体也是如此。RopGEF 1过表达表型被ROP 1的显性负突变体表达抑制，可能是通过捕获RopGEF 1。缺失突变体分析表明RopGEF 1在极性生长中的功能需要RopGEF活性。绿色荧光蛋白标记的RopGEF 1定位于ROP 1被激活的花粉管尖端。这些结果提供了强有力的证据表明，RopGEF 1激活ROP 1在控制花粉管极性生长。
Rho family small GTPases are signaling switches controlling many eukaryotic cellular processes. Conversion from the GDP- to GTP-bound form is catalyzed by guanine nucleotide exchange factors ( GEFs). Rho GEFs in animals fall into two structurally distinct classes containing DH and DOCKER catalytic domains. Using a plant Rho GTPase (ROP1) as bait in yeast two-hybrid screens, we identified a family of Rho GEFs, named RopGEFs. The Arabidopsis thaliana RopGEF family of 14 members contains a conserved central domain, the domain of unknown function 315 (DUF315), and variable N- and C-terminal regions. In vitro GEF assays show that DUF315 but not the full-length version of RopGEF1 has high GEF activity toward ROP1. Our data suggest that the variable regions of RopGEF1 are involved in regulation of RopGEF through an autoinhibitory mechanism. RopGEF1 overexpression in pollen tubes produced growth depolarization, as does a constitutively active ROP1 mutant. The RopGEF1 overexpression phenotype was suppressed by expression of a dominant-negative mutant of ROP1, probably by trapping RopGEF1. Deletion mutant analysis suggested a requirement of RopGEF activity for the function of RopGEF1 in polar growth. Green fluorescent protein - tagged RopGEF1 was localized to the tip of pollen tubes where ROP1 is activated. These results provide strong evidence that RopGEF1 activates ROP1 in control of polar growth in pollen tubes.