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Plant Physiol. 2018 Apr;176(4):2720-2736. doi: 10.1104/pp.17.01563. Epub 2018 Feb 8.

Comparative Analysis of Arabidopsis Ecotypes Reveals a Role for Brassinosteroids in Root Hydrotropism.

Author information

1
Center for Plant Water-Use and Nutrition Regulation and College of Life Sciences, Joint International Research Laboratory of Water and Nutrient in Crops, Fujian Agriculture and Forestry University, Jinshan Fuzhou 350002, China.
2
Department of Biology, Hong Kong Baptist University, and Stake Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Hong Kong.
3
Department of Biology, Hong Kong Baptist University, and Stake Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Hong Kong jhzhang@cuhk.edu.hk wfxu@fafu.edu.cn.
4
School of BioSciences, University of Melbourne, Parkville, Victoria 3010, Australia.
5
Center for Plant Water-Use and Nutrition Regulation and College of Life Sciences, Joint International Research Laboratory of Water and Nutrient in Crops, Fujian Agriculture and Forestry University, Jinshan Fuzhou 350002, China jhzhang@cuhk.edu.hk wfxu@fafu.edu.cn.

Abstract

Plant roots respond to soil moisture gradients and remodel their growth orientation toward water through hydrotropism, a process vital for acclimation to a changing soil environment. Mechanisms underlying the root hydrotropic response, however, remain poorly understood. Here, we examined hydrotropism in 31 Arabidopsis (Arabidopsis thaliana) ecotypes collected from different parts of the world and grown along moisture gradients in a specially designed soil-simulation system. Comparative transcriptome profiling and physiological analyses were carried out on three selected ecotypes, Wassilewskija (Ws), Columbia (Col-0) (strongly hydrotropic), Col-0 (moderately hydrotropic), and C24 (weakly hydrotropic), and in mutant lines with altered root hydrotropic responses. We show that H+ efflux, Ca2+ influx, redox homeostasis, epigenetic regulation, and phytohormone signaling may contribute to root hydrotropism. Among phytohormones, the role of brassinosteroids (BRs) was examined further. In the presence of an inhibitor of BR biosynthesis, the strong hydrotropic response observed in Ws was reduced. The root H+ efflux and primary root elongation also were inhibited when compared with C24, an ecotype that showed a weak hydrotropic response. The BR-insensitive mutant bri1-5 displayed higher rates of root growth inhibition and root curvature on moisture gradients in vertical or oblique orientation when compared with wild-type Ws. We also demonstrate that BRI1 (a BR receptor) interacts with AHA2 (a plasma membrane H+-ATPase) and that their expression patterns are highly coordinated. This synergistic action may contribute to the strong hydrotropism observed in Ws. Our results suggest that BR-associated H+ efflux is critical in the hydrotropic response of Arabidopsis roots.

PMID:
29439211
PMCID:
PMC5884606
DOI:
10.1104/pp.17.01563
[Indexed for MEDLINE]
Free PMC Article

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