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The auxin influx carrier LAX3 promotes lateral root emergence

Abstract

Lateral roots originate deep within the parental root from a small number of founder cells at the periphery of vascular tissues and must emerge through intervening layers of tissues. We describe how the hormone auxin, which originates from the developing lateral root, acts as a local inductive signal which re-programmes adjacent cells. Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia. Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell-wall-remodelling enzymes, which are likely to promote cell separation in advance of developing lateral root primordia.

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Figure 1: AUX1 and LAX3 are required for lateral root development.
Figure 2: LAX3 encodes a high-affinity auxin influx carrier.
Figure 3: LAX3 is expressed in mature tissues adjacent to developing LRP.
Figure 4: LAX3 regulates the expression of cell-wall-remodelling enzymes.
Figure 5: Lateral root emergence relies on an aerial source of auxin in a concentration-dependent manner.
Figure 6: LAX3 expression is positively regulated by auxin.
Figure 7: LAX3 is upregulated by auxin in an ARF and IAA14-dependent manner.
Figure 8: Model for auxin-dependent lateral root emergence.

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Acknowledgements

We would like to thank the Nottingham Arabidopsis Stock Centre (NASC), Hidehiro Fukaki, Tom Guilfoyle, Jason Reed, Sakis Theologis and Bert van der Zaal for providing seed and constructs used in this study. We also thank Jerry Roberts, Graham Seymour, Klaus Palme, Angus Murphy and the anonymous referees for helpful feedback about the work. We acknowledge the support of the Biotechnology and Biological Sciences Research Council (K.S., R.S., G.P., N.J., R.R., N.G., S.M. and M.J.B.); BBSRC/EPSRC CISB programme funding (M.J.B.); European Space Agency (R.S. and M.J.B.); European Commission Framework V Popwood programme (R.S. and M.J.B.); Gatsby Charitable Foundation (M.J.B.); Belgian Scientific policy (BELSPO contract BARN to M.J.B.and T.B.); Margarete von Wrangell-Habilitationsprogramm (E.B); Junta de Extremadura, MOV05A016 (I.C.); IRD (B.P and L.L.); British Council/Egide Alliance grant (No. 05752SM to L.L and M.J.B.); Federation of European Biochemical Societies fellowship funding (B.P.); European Molecular Biology Organization fellowship funding (EMBO, ALTF 142-2007 (S.V.) and ALTF 108-2006 (I.D.S.)); the Institute for the Promotion of Innovation through Science and Technology in Flanders for predoctoral fellowships (I.D.S. and S.V.); Research Foundation – Flanders (FWO) (I.D.S.); National Science Foundation USA #0344265 (E.N, D.P.S. and C.G.T.); and the NSF AT2010 program (P.N.B.).

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Correspondence to Malcolm J. Bennett.

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Supplementary Figures S1, S2, S3, S4, S5 and S6 (PDF 1633 kb)

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Swarup, K., Benková, E., Swarup, R. et al. The auxin influx carrier LAX3 promotes lateral root emergence. Nat Cell Biol 10, 946–954 (2008). https://doi.org/10.1038/ncb1754

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