A Role for the TOC Complex in Arabidopsis Root Gravitropism
A Role for the TOC Complex in Arabidopsis Root Gravitropism
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DOI：
10.1104/pp.109.135301
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发表时间：
2009-04-01
期刊：
影响因子：
7.4
通讯作者：
Masson, Patrick H.
中科院分区：
文献类型：
--
作者：
Stanga, John P.;Boonsirichai, Kanokporn;Masson, Patrick H.
拟南芥（Arabidopsis thaliana）的根感知重力并相应地重新定向其生长。淀粉致密的淀粉质体内的柱头细胞的根冠是重要的向重力性，和无淀粉突变体，如pgm 1显示一个衰减的反应重力刺激。arg 1突变体与重力信号转导的早期阶段有关。arg 1对重力刺激反应缓慢，并且与pgm 1在遗传上不同，因为pgm 1突变体增强了arg 1的向重力缺陷。arg 1种子用甲基磺酸乙酯诱变以鉴定增强arg 1向重力性缺陷的新突变体。arg 1突变体（mar 1和mar 2）的两个修改器仅在arg 1存在时才以随机方向生长，不影响向光性，并像野生型一样对植物激素的应用作出反应。两者都具有影响叶绿体外膜易位子（TOC）复合物的不同组分的突变。mar 1在TOC 75-III基因中具有突变; mar 2在TOC 132基因中具有突变。TOC 132的过表达拯救了mar 2 arg 1根的随机生长表型。mar 2 arg 1的根冠造粉体超微结构正常。它们像野生型一样跳跃，并在重力刺激下以野生型速率沉积。这些数据点的作用，质体TOC复合物的重力信号转导内的平衡细胞。
Arabidopsis (Arabidopsis thaliana) roots perceive gravity and reorient their growth accordingly. Starch-dense amyloplasts within the columella cells of the root cap are important for gravitropism, and starchless mutants such as pgm1 display an attenuated response to gravistimulation. The altered response to gravity1 (arg1) mutant is known to be involved with the early phases of gravity signal transduction. arg1 responds slowly to gravistimulation and is in a genetically distinct pathway from pgm1, as pgm1 mutants enhance the gravitropic defect of arg1. arg1 seeds were mutagenized with ethylmethane sulfonate to identify new mutants that enhance the gravitropic defect of arg1. Two modifier of arg1 mutants (mar1 and mar2) grow in random directions only when arg1 is present, do not affect phototropism, and respond like the wild type to application of phytohormones. Both have mutations affecting different components of the Translocon of Outer Membrane of Chloroplasts (TOC) complex. mar1 possesses a mutation in the TOC75-III gene; mar2 possesses a mutation in the TOC132 gene. Overexpression of TOC132 rescues the random growth phenotype of mar2 arg1 roots. Root cap amyloplasts in mar2 arg1 appear ultrastructurally normal. They saltate like the wild type and sediment at wild-type rates upon gravistimulation. These data point to a role for the plastidic TOC complex in gravity signal transduction within the statocytes.