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PtdIns(3,5)P2 mediates root hair shank hardening in Arabidopsis


Root hairs elongate by tip growth and simultaneously harden the shank by constructing the inner secondary cell wall layer. While much is known about the process of tip growth1, almost nothing is known about the mechanism by which root hairs harden the shank. Here we show that phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), the enzymatic product of FORMATION OF APLOID AND BINUCLEATE CELLS 1 (FAB1), is involved in the hardening of the shank in root hairs in Arabidopsis. FAB1 and PtdIns(3,5)P2 localize to the plasma membrane along the shank of growing root hairs. By contrast, phosphatidylinositol 4-phosphate 5-kinase 3 (PIP5K3) and PtdIns(4,5)P2 localize to the apex of the root hair where they are required for tip growth. Reduction of FAB1 function results in the formation of wavy root hairs while those of the wild type are straight. The localization of FAB1 in the plasma membrane of the root hair shank requires the activity of Rho-related GTPases from plants 10 (ROP10) and localization of ROP10 requires FAB1 activity. Computational modelling of root hair morphogenesis successfully reproduces the wavy root hair phenotype. Taken together, these data demonstrate that root hair shank hardening requires PtdIns(3,5)P2/ROP10 signalling.

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Change history

  • 01 April 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.


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We thank T. Miura (Kyushu University, Japan) for his helpful comments on the computational model, T. Nakagawa (Shimane University, Japan) for providing pGWB vectors, C. Ambrose (University of Saskatchewan, Canada) for providing the GFP–MBD-expressing line, T. Hashimoto (NAIST, Japan) for providing the EB1b–GFP-expression line, Y. Jailais (Université de Lyon, France) for providing the CITRINE–2:PHPLC-expressing line and fruitful discussion, and Y. Oda (National Institute for Genetics, Japan) and S. Sakamoto and N. Mitsuda (National Institute of Advanced Industrial Science and Technology, Japan) for fruitful discussion about cell wall components. We thank T. Ando and N. Kodera (Kanazawa University) for providing us with experimental instruments, and T. Nakayama-Watanabe for critical suggestions for data analysis. We also thank K. Tamura and I. Hara-Nishimura (Kyoto University) for fruitful discussion. This work was supported by JSPS KAKENHIJP16H05068 to M.H.S., JP17K08200 to T. Hirano, JP18K06260 to H.T.-I, JP16K06260 to T.A., 16KT0170 to T.A., 17K15238 to M.K., JP16H06280, 17K19380, 18H05492, a Grant for Basic Science Research Projects from The Sumitomo Foundation (160146), and a Grant from The Canon Foundation to T. Higaki, Marie Curie Actions; Incoming Interaction Fellowship (ID: 022275) to S.T.

Author information

T. Hirano, M.K., T.A. and M.H.S. conceived and designed the study. T. Hirano and S.T. performed the experiments. H.K. performed AFM. H.T.-I. and T. Higaki performed the mathematical modelling. T. Hirano, S.T., L.D., M.K., T.A., T. Higaki, H.T.-I. and M.H.S. analysed the data. T. Hirano, H.T-I., L.D. and M.H.S. wrote the manuscript. M.H.S. supervised the project.

Competing interests

The authors declare no competing interests.

Correspondence to Masa H. Sato.

Supplementary information

Supplementary Information

Supplementary Figures 1–19 and Supplementary Video legends.

Reporting Summary

Supplementary Table 1

List of materials used for this study.

Supplementary Video 1

Time lapse images PI(3,5)P2 and PI(4,5)P2 fluorescence of initiation step of root hair elongation.

Supplementary Video 2

Time lapse images PtdIns(3,5)P2 and PtdIns(4,5)P2 fluorescence of elongating step of root hair.

Supplementary Video 3

Time lapse images PtdIns(3,5)P2 and PtdIns(4,5)P2 fluorescence of termination step of root hair elongation.

Supplementary Video 4

Computer simulation of the growing process of the wild type root hair in the air.

Supplementary Video 5

Computer simulation of the growing process of the wild type root hair in the gel.

Supplementary Video 6

Computer simulation of the wavy root hair in the air.

Supplementary Video 7

Computer simulation of the wavy root hair in the gel.

Supplementary Video 8

Computer simulation of the swollen root hair in the air.

Supplementary Video 9

Computer simulation of the swollen root hair in the gel.

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Further reading

Fig. 1: FAB1A and PIP5K3 and their enzymatic products, PtdIns(3,5)P2 and PtdIns(4,5)P2, exclusively localized to the plasma membrane of the shank and apex of elongating root hair respectively, and reduced FAB1 function caused a wavy root hair shape.
Fig. 2: The stiffness of the root hair shank, the deposition of xylan and the organization of the cortical microtubule array of the root hair were affected by reduced FAB1A and FAB1B expression.
Fig. 3: ROP10 controls root hair shank formation.
Fig. 4: ROP10 specifically interacts with FAB1A in root hair cells, and they determine the shank PM localization of each other.