Arabidopsis SPIRAL2 promotes uninterrupted microtubule growth by suppressing the pause state of microtubule dynamics
Arabidopsis SPIRAL2 promotes uninterrupted microtubule growth by suppressing the pause state of microtubule dynamics
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DOI：
10.1242/jcs.030221
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发表时间：
2008-07-15
影响因子：
4
通讯作者：
Hashimoto, Takashi
中科院分区：
文献类型：
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作者：
Yao, Maki;Wakamatsu, Yoshinori;Hashimoto, Takashi
拟南芥的 SPIRAL2 (SPR2) 是一种微管相关蛋白，含有仅在植物谱系中发现的多个 HEAT 重复序列。我们发现 SPR2 和 SP2L（它们最接近的拟南芥同源物）在各种组织中以部分重叠的模式表达，并且 spr2-sp2l 双突变体表现出增强的右手螺旋生长。与在天然调控元件控制下表达的绿色荧光蛋白（GFP）的融合表明，SPR2和SP2L都定位于皮质微管，主要以各种尺寸的颗粒形式存在。沿着微管，GFP融合形式也部分分布在正端。在spr2突变背景下，皮质微管的动态性较低，暂停状态（微管既不生长也不收缩）在正端增加。 GFP-EB1 的连续正端追踪在突变细胞中偶尔会被中断。重组SPR2蛋白促进微管聚合，并与具有包含两个HEAT重复序列的N端片段的微管以及具有C端区域的微管结合。微管动力学的体外分析表明，SPR2 和 SP2L 抑制微管末端的暂停状态，从而促进微管生长。我们建议 SPR2 家族蛋白作用于暂停状态，以促进向微管生长的过渡。
SPIRAL2 (SPR2) of Arabidopsis thaliana is a microtubule-associated protein containing multiple HEAT repeats that are found only in the plant lineage. We show that SPR2 and SP2L, their closest Arabidopsis homolog, are expressed in various tissues with partially overlapping patterns, and spr2-sp2l double mutants exhibit enhanced right-handed helical growth. Fusion to green fluorescent protein (GFP) expressed under the control of the native regulatory elements showed that both SPR2 and SP2L were localized to cortical microtubules, mainly in particles of various sizes. Along the microtubule, the GFP-fused forms also distributed partly at the plus ends. In the spr2-mutant background, cortical microtubules were less dynamic, and the pause state - in which microtubules undergo neither growth nor shrinkage - increased at the plus ends. The continuous plusend tracking of GFP-EB1 was occasionally interrupted in the mutant cells. Recombinant SPR2 protein promoted microtubule polymerization, and bound to microtubules with an N-terminal segment that contained two HEAT repeats as well as to those with a C-terminal region. In vitro analyses of microtubule dynamics revealed that SPR2 and SP2L suppressed the pause state at microtubule ends, thereby leading to enhanced microtubule growth. We propose that the SPR2-family proteins act on the pause state to facilitate a transition to microtubule growth.