Li Ying, Yuan Wei, Li Luocheng, Dai Hui, Dang Xiaolin, Miao Rui, Baluška František, Kronzucker Herbert J, Lu Congming, Zhang Jianhua, Xu Weifeng
Center for Plant Water-use and Nutrition Regulation and College of Life Sciences, Joint International Research Laboratory of Water and Nutrient in Crop and college of Resource and Environment, Fujian Agriculture and Forestry University, Jinshan, Fuzhou, China.
Institute of Cellular and Molecular Botany, University of Bonn, Bonn, Germany.
J Exp Bot. 2020 Dec 31;71(22):7316-7330. doi: 10.1093/jxb/eraa409.
Hydrotropism is the directed growth of roots toward the water found in the soil. However, mechanisms governing interactions between hydrotropism and gravitropism remain largely unclear. In this study, we found that an air system and an agar-sorbitol system induced only oblique water-potential gradients; an agar-glycerol system induced only vertical water-potential gradients; and a sand system established both oblique and vertical water-potential gradients. We employed obliquely oriented and vertically oriented experimental systems to study hydrotropism in Arabidopsis and tomato plants. Comparative analyses using different hydrotropic systems showed that gravity hindered the ability of roots to search for obliquely oriented water, whilst facilitating roots' search for vertically oriented water. We found that the gravitropism-deficient mutant aux1 showed enhanced hydrotropism in the oblique orientation but impaired root elongation towards water in the vertical orientation. The miz1 mutant exhibited deficient hydrotropism in the oblique orientation but normal root elongation towards water in the vertical orientation. Importantly, in contrast to miz1, the miz1/aux1 double mutant exhibited hydrotropic bending in the oblique orientation and attenuated root elongation towards water in the vertical orientation. Our results suggest that gravitropism is required for MIZ1-regulated root hydrotropism in both the oblique orientation and the vertical orientation, providing further insight into the role of gravity in root hydrotropism.
向水性是指植物根系朝着土壤中水分的定向生长。然而，关于向水性与向地性之间相互作用的机制在很大程度上仍不清楚。在本研究中，我们发现空气系统和琼脂 - 山梨醇系统仅诱导倾斜的水势梯度；琼脂 - 甘油系统仅诱导垂直的水势梯度；而沙子系统则同时建立了倾斜和垂直的水势梯度。我们采用倾斜定向和垂直定向的实验系统来研究拟南芥和番茄植株的向水性。使用不同向水系统的比较分析表明，重力阻碍了根系寻找倾斜方向水分的能力，同时促进了根系寻找垂直方向水分的能力。我们发现向地性缺陷突变体aux1在倾斜方向上表现出增强的向水性，但在垂直方向上根系向水伸长受损。miz1突变体在倾斜方向上表现出向水性缺陷，但在垂直方向上根系向水伸长正常。重要的是，与miz1相反，miz1/aux1双突变体在倾斜方向上表现出向水弯曲，而在垂直方向上根系向水伸长减弱。我们的结果表明，向地性对于MIZ1调控的根系在倾斜方向和垂直方向上的向水性都是必需的，这为重力在根系向水性中的作用提供了进一步的见解。
