Key Laboratory of the Ministry of Education for Medicinal Plant Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in the Northwest of China, College of Life Sciences, Shaanxi Normal University, No. 620, West Chang'an Avenue, Chang'an District, Xi'an, 710119, China.
Institute of Science and Technology (IST) Austria, 3400, Klosterneuburg, Austria.
New Phytol. 2019 Oct;224(2):761-774. doi: 10.1111/nph.15932. Epub 2019 Jun 23.
Root gravitropism is one of the most important processes allowing plant adaptation to the land environment. Auxin plays a central role in mediating root gravitropism, but how auxin contributes to gravitational perception and the subsequent response are still unclear. Here, we showed that the local auxin maximum/gradient within the root apex, which is generated by the PIN directional auxin transporters, regulates the expression of three key starch granule synthesis genes, SS4, PGM and ADG1, which in turn influence the accumulation of starch granules that serve as a statolith perceiving gravity. Moreover, using the cvxIAA-ccvTIR1 system, we also showed that TIR1-mediated auxin signaling is required for starch granule formation and gravitropic response within root tips. In addition, axr3 mutants showed reduced auxin-mediated starch granule accumulation and disruption of gravitropism within the root apex. Our results indicate that auxin-mediated statolith production relies on the TIR1/AFB-AXR3-mediated auxin signaling pathway. In summary, we propose a dual role for auxin in gravitropism: the regulation of both gravity perception and response.
根向地性是植物适应陆地环境的最重要过程之一。生长素在介导根向地性中起着核心作用，但生长素如何参与重力感知以及随后的响应仍不清楚。在这里，我们表明，由 PIN 定向生长素转运蛋白在根尖内产生的局部生长素最大值/梯度，调节三个关键淀粉粒合成基因 SS4、PGM 和 ADG1 的表达，进而影响作为重质体感知重力的淀粉粒的积累。此外，我们还利用 cvxIAA-ccvTIR1 系统表明，TIR1 介导的生长素信号转导对于根尖内淀粉粒的形成和向地性反应是必需的。此外，axr3 突变体表现出减少的生长素介导的淀粉粒积累和根尖端向地性的破坏。我们的结果表明，生长素介导的重质体产生依赖于 TIR1/AFB-AXR3 介导的生长素信号通路。总之，我们提出生长素在向地性中具有双重作用：既调节重力感知又调节响应。
