Helical Growth of the Arabidopsis Mutant tortifolia2 Does Not Depend on Cell Division Patterns but Involves Handed Twisting of Isolated Cells
Helical Growth of the Arabidopsis Mutant tortifolia2 Does Not Depend on Cell Division Patterns but Involves Handed Twisting of Isolated Cells
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DOI：
10.1105/tpc.108.061242
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发表时间：
2009-07-01
期刊：
影响因子：
11.6
通讯作者：
Schaeffner, Anton R.
中科院分区：
文献类型：
--
作者：
Buschmann, Henrik;Hauptmann, Monika;Schaeffner, Anton R.
有几个因素调节植物器官的生长极性。tortifolia 2（tor 2）是一种右旋螺旋生长突变体，在α-微管蛋白4蛋白中具有Arg-2被Lys的保守替换。基于已发表的高分辨率（2.89埃）微管蛋白结构，我们预测，精氨酸-2的α-微管蛋白形成氢键与β-微管蛋白的GTdR结构域，和结构建模表明，这些接触中断tor 2。与此一致，我们发现微管动力学在tor 2背景下降低。我们使用tor 2研究了螺旋生长表型的发育起源。一种假说预测细胞分裂模式导致拟南芥突变体的螺旋状器官生长。然而，tor 2根尖细胞分裂模式似乎正常。细胞分裂和扩张的实验解偶联表明，螺旋状器官生长仅基于细胞伸长缺陷。另一种假设是，扭曲是由于表皮和皮质组织扩张的不平等。然而，tor 2突变体自由生长的叶毛早在毛状体发育的无分支阶段就表现出右旋扭曲，皮质微管形成左旋螺旋。毛状体扭曲是反转的双突变体与tor 3，左手突变体。单tor 2悬浮细胞也表现出手扭转。因此，扭曲的tor 2突变体器官似乎是一个更高阶的表达个别细胞的螺旋扩张。
Several factors regulate plant organ growth polarity. tortifolia2 (tor2), a right-handed helical growth mutant, has a conservative replacement of Arg-2 with Lys in the alpha-tubulin 4 protein. Based on a published high-resolution (2.89 angstrom) tubulin structure, we predict that Arg-2 of alpha-tubulin forms hydrogen bonds with the GTPase domain of beta-tubulin, and structural modeling suggests that these contacts are interrupted in tor2. Consistent with this, we found that microtubule dynamicity is reduced in the tor2 background. We investigated the developmental origin of the helical growth phenotype using tor2. One hypothesis predicts that cell division patterns cause helical organ growth in Arabidopsis thaliana mutants. However, cell division patterns of tor2 root tips appear normal. Experimental uncoupling of cell division and expansion suggests that helical organ growth is based on cell elongation defects only. Another hypothesis is that twisting is due to inequalities in expansion of epidermal and cortical tissues. However, freely growing leaf trichomes of tor2 mutants show right-handed twisting and cortical microtubules form left-handed helices as early as the unbranched stage of trichome development. Trichome twisting is inverted in double mutants with tor3, a left-handed mutant. Single tor2 suspension cells also exhibit handed twisting. Thus, twisting of tor2 mutant organs appears to be a higher-order expression of the helical expansion of individual cells.