The Lateral Root Cap Acts as an Auxin Sink that Controls Meristem Size.

Published

Journal Article

Plant developmental plasticity relies on the activities of meristems, regions where stem cells continuously produce new cells [1]. The lateral root cap (LRC) is the outermost tissue of the root meristem [1], and it is known to play an important role during root development [2-6]. In particular, it has been shown that mechanical or genetic ablation of LRC cells affect meristem size [7, 8]; however, the molecular mechanisms involved are unknown. Root meristem size and, consequently, root growth depend on the position of the transition zone (TZ), a boundary that separates dividing from differentiating cells [9, 10]. The interaction of two phytohormones, cytokinin and auxin, is fundamental in controlling the position of the TZ [9, 10]. Cytokinin via the ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) control auxin distribution within the meristem, generating an instructive auxin minimum that positions the TZ [10]. We identify a cytokinin-dependent molecular mechanism that acts in the LRC to control the position of the TZ and meristem size. We show that auxin levels within the LRC cells depends on PIN-FORMED 5 (PIN5), a cytokinin-activated intracellular transporter that pumps auxin from the cytoplasm into the endoplasmic reticulum, and on irreversible auxin conjugation mediated by the IAA-amino synthase GRETCHEN HAGEN 3.17 (GH3.17). By titrating auxin in the LRC, the PIN5 and the GH3.17 genes control auxin levels in the entire root meristem. Overall, our results indicate that the LRC serves as an auxin sink that, under the control of cytokinin, regulates meristem size and root growth.

Full Text

Duke Authors

Cited Authors

  • Di Mambro, R; Svolacchia, N; Dello Ioio, R; Pierdonati, E; Salvi, E; Pedrazzini, E; Vitale, A; Perilli, S; Sozzani, R; Benfey, PN; Busch, W; Costantino, P; Sabatini, S

Published Date

  • April 2019

Published In

Volume / Issue

  • 29 / 7

Start / End Page

  • 1199 - 1205.e4

PubMed ID

  • 30880016

Pubmed Central ID

  • 30880016

Electronic International Standard Serial Number (EISSN)

  • 1879-0445

International Standard Serial Number (ISSN)

  • 0960-9822

Digital Object Identifier (DOI)

  • 10.1016/j.cub.2019.02.022

Language

  • eng