PIN‐mediated polar auxin transport facilitates root−obstacle avoidance

First author: Hyo‐Jun Lee; Affiliations: Korea Research Institute of Bioscience and Biotechnology (韩国生物科学与技术研究所): Daejeon, Korea

Corresponding author: Hyo‐Jun Lee

Plants sense mechanical stimuli to recognise nearby obstacles and change their growth patterns to adapt to the surrounding environment. When roots encounter an obstacle, they rapidly bend away from the impenetrable surface and find the edge of the barrier. However, the molecular mechanisms underlying root−obstacle avoidance are largely unknown. Here, we demonstrate that PIN‐FORMED (PIN)‐mediated polar auxin transport facilitates root bending during obstacle avoidance. We analysed two types of bending after roots touched barriers. In auxin receptor mutants, the rate of root movement during first bending was largely delayed. Gravity‐oriented second bending was also disturbed in these mutants. The reporter assays showed that asymmetrical auxin responses occurred in the roots during obstacle avoidance. Pharmacological analysis suggested that polar auxin transport mediates local auxin accumulation. We found that PINs are required for auxin‐assisted root bending during obstacle avoidance. We propose that rapid root movement during obstacle avoidance is not just a passive but an active bending completed through polar auxin transport. Our findings suggest that auxin plays a role in thigmotropism (向触性) during plant−obstacle interactions.

植物通过感知机械刺激来识别附近的障碍物并改变其生长方式以适应周围环境。当植物根组织遇到障碍物时，它们会迅速弯曲，从无法穿透的障碍物表面移开并找到其边缘。然而，根的障碍物躲避机制还不清楚。本文中，作者证明了PIN蛋白介导的极性生长素运输在避障过程中作用于根的弯曲。作者分析了根在接触障碍物后的两种弯曲类型。在生长素受体突变体中，第一次弯曲时根部移动的速度发生了大幅度延迟。在这些突变体中，重力导向的第二次弯曲也受到了干扰。受体试验表明，避障过程中根部发生了不对称的生长素响应。药理分析显示极性生长素运输介导了局部的生长素积累。作者发现PIN对于避障过程中生长素辅助的根部弯曲是必需的。作者认为，在避障过程中根部的快速移动不仅是被动的，而且是通过极性生长素运输完成的主动弯曲。本文的研究结果表明，生长素作用于植物与障碍物相互作用期间的向触性。（p.s. Thigmotropism is the directional response of a plant organ to touch or physical contact with a solid object. 向触性是指植物器官在触碰或物理接触某个固体物体时发生的方向性响应。)

通讯：Hyo-Jun Lee  (https://www.kribb.re.kr/eng/sub02/sub02_03_01.jsp)

研究方向：植物适应环境变化的分子机制。

doi: https://doi.org/10.1111/nph.16076

Journal: New Phytologist

First Published: July 23, 2019