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A RhoGDP dissociation inhibitor spatially regulates growth in root hair cells


Root hairs are cellular protuberances extending from the root surface into the soil; there they provide access to immobile inorganic ions such as phosphate, which are essential for growth1. Their cylindrical shape results from a polarized mechanism of cell expansion called tip growth in which elongation is restricted to a small area at the surface of the hair-forming cell (trichoblast) tip2,3,4. Here we identify proteins that spatially control the sites at which cell growth occurs by isolating Arabidopsis mutants (scn1) that develop ectopic sites of growth on trichoblasts. We cloned SCN1 and showed that SCN1 is a RhoGTPase GDP dissociation inhibitor (RhoGDI) that spatially restricts the sites of growth to a single point on the trichoblast. We showed previously that localized production of reactive oxygen species by RHD2/AtrbohC NADPH oxidase is required for hair growth5; here we show that SCN1/AtrhoGDI1 is a component of the mechanism that focuses RHD2/AtrbohC-catalysed production of reactive oxygen species to hair tips during wild-type development. We propose that the spatial organization of growth in plant cells requires the local RhoGDI-regulated activation of the RHD2/AtrbohC NADPH oxidase.

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Figure 1: Phenotype of scn1 roots. Roots of 5-day-old seedlings.
Figure 2: ROS localization and hair growth.
Figure 3: Phenotype of scn1 rhd2 double mutant showing that the multiple hair-initiation phenotype characteristic of scn1 mutant is suppressed in the rhd2 mutant background.


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We thank F. Cvrckova for the anti-Rop antibody, C. S. Grierson for providing scn1-1 seeds, and B. Scheres and J. Xu for providing the ROP2::YFP fusion construct and ROP2::YFP-transformed seed. S.T. is supported by a grant from the BBSRC to L.D., who is also supported by EU TIPNET. R.C., L.D. and M.D. are funded by a grant-in-aid to the John Innes Centre by the BBSRC. P.D. and S.D. were supported by grants to L.D., P. Shaw and J. Doonan and from Syngenta and the BBSRC. V.Z. and H.K. are funded by EU TIPNET and GACR (Grant Agency of Czech Republic).

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Correspondence to Liam Dolan.

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Supplementary information

Supplementary Figure 1

NBT-stained growing and non-growing root hairs. (JPG 114 kb)

Supplementary Figure 2

Cloning, sequence analysis and expression of SCN1/AtRhoGDI1. (PDF 5957 kb)

Supplementary Figure 3

Interaction between scn1-2 and ROP proteins is defective in vitro. (PDF 1484 kb)

Supplementary Figure 4

SCN1 regulates the subcellular localisation of ROP2 protein. (PDF 18138 kb)

Supplementary Figure 5

Primers used in this study. (DOC 25 kb)

Supplementary Figure Legends

Text to accompany the above Supplementary Figures. (DOC 27 kb)

Supplementary Methods

Additional descriptions of the methods used in this study. (DOC 32 kb)

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Carol, R., Takeda, S., Linstead, P. et al. A RhoGDP dissociation inhibitor spatially regulates growth in root hair cells. Nature 438, 1013–1016 (2005).

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