Unifying model of shoot gravitropism reveals proprioception as a central feature of posture control in plants
Unifying model of shoot gravitropism reveals proprioception as a central feature of posture control in plants
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DOI：
10.1073/pnas.1214301109
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发表时间：
2013-01-08
影响因子：
11.1
通讯作者：
Douady, Stephane
中科院分区：
文献类型：
--
作者：
Bastien, Renaud;Bohr, Tomas;Douady, Stephane
向地性，即植物生长响应重力的缓慢重新定向，是陆地植物形态和姿态的关键决定因素。当静囊感知到生长器官相对于重力场的局部角度时，就会触发芽的向地性。然后，生长素激素向下侧的横向运输得到增强，导致基因表达差异和细胞伸长，导致器官弯曲。然而，人们对整个弯曲和矫直过程的动力学、调节和多样性知之甚少。在这里，我们模拟了杆状器官的弯曲和伸直，并将其与 11 种被子植物不同器官的向地性运动学进行了比较。我们表明，向重力矫直在不同物种、器官和数量级上具有共同特征。解释这些特征的最小动态模型不是广泛引用的重力感应定律，而是还考虑了局部曲率感应的模型，我们在这里将其描述为重力本体感觉定律。在我们的模型中，弯曲/伸直响应的整个动力学由单个无量纲“弯曲数”B 来描述，它反映了重力感受和本体感受敏感性之间的比率。参数 B 定义了器官平衡时的最终形状以及弯曲和伸直的时间。 B 可以通过简单的实验来估计，然后该模型可以解释实验中观察到的大部分多样性。因此，本体感觉与重力控制中的重力感觉一样重要，并且 B 比率可以作为遗传研究中的表型来测量。
Gravitropism, the slow reorientation of plant growth in response to gravity, is a key determinant of the form and posture of land plants. Shoot gravitropism is triggered when statocysts sense the local angle of the growing organ relative to the gravitational field. Lateral transport of the hormone auxin to the lower side is then enhanced, resulting in differential gene expression and cell elongation causing the organ to bend. However, little is known about the dynamics, regulation, and diversity of the entire bending and straightening process. Here, we modeled the bending and straightening of a rod-like organ and compared it with the gravitropism kinematics of different organs from 11 angiosperms. We show that gravitropic straightening shares common traits across species, organs, and orders of magnitude. The minimal dynamic model accounting for these traits is not the widely cited gravisensing law but one that also takes into account the sensing of local curvature, what we describe here as a graviproprioceptive law. In our model, the entire dynamics of the bending/straightening response is described by a single dimensionless "bending number" B that reflects the ratio between graviceptive and proprioceptive sensitivities. The parameter B defines both the final shape of the organ at equilibrium and the timing of curving and straightening. B can be estimated from simple experiments, and the model can then explain most of the diversity observed in experiments. Proprioceptive sensing is thus as important as gravisensing in gravitropic control, and the B ratio can be measured as phenotype in genetic studies.