An auxin transport mechanism restricts positive orthogravitropism in lateral roots Journal Article

Author(s): Rosquete, Michel R; von Wangenheim, Daniel; Marhavý, Peter; Barbez, Elke; Stelzer, Ernst H; Benková, Eva; Maizel, Alexis; Kleine-Vehn, Jürgen
Article Title: An auxin transport mechanism restricts positive orthogravitropism in lateral roots
Affiliation IST Austria
Abstract: As soon as a seed germinates, plant growth relates to gravity to ensure that the root penetrates the soil and the shoot expands aerially. Whereas mechanisms of positive and negative orthogravitropism of primary roots and shoots are relatively well understood [1-3], lateral organs often show more complex growth behavior [4]. Lateral roots (LRs) seemingly suppress positive gravitropic growth and show a defined gravitropic set-point angle (GSA) that allows radial expansion of the root system (plagiotropism) [3, 4]. Despite its eminent importance for root architecture, it so far remains completely unknown how lateral organs partially suppress positive orthogravitropism. Here we show that the phytohormone auxin steers GSA formation and limits positive orthogravitropism in LR. Low and high auxin levels/signaling lead to radial or axial root systems, respectively. At a cellular level, it is the auxin transport-dependent regulation of asymmetric growth in the elongation zone that determines GSA. Our data suggest that strong repression of PIN4/PIN7 and transient PIN3 expression limit auxin redistribution in young LR columella cells. We conclude that PIN activity, by temporally limiting the asymmetric auxin fluxes in the tip of LRs, induces transient, differential growth responses in the elongation zone and, consequently, controls root architecture.
Keywords: Columella
Journal Title: Current Biology
Volume: 23
Issue 9
ISSN: 0960-9822
Publisher: Cell Press  
Date Published: 2013-05-06
Start Page: 817
End Page: 822
Sponsor: ERC starting independent research grant ERC-2007-Stg-207362-HCPO (to P.M., E. Benkova)
DOI: 10.1016/j.cub.2013.03.064
Notes: We are grateful to Jim Haseloff, Ben Scheres, Jiri Friml, and Ykä Helariuta for sharing published material; Stefan Kepinsky, Chris Wolverton, and KV group members for helpful comments; David Whittaker for help in preparing the manuscript; and the BOKU-VIBT Imaging Center for access and expertise.
Open access: no