JLO regulates embryo patterning and organ initiation by controlling auxin transport

Abstract

In Arabidopsis, lateral organ initiation correlates with the formation of an auxin maximum in a group of cells at the periphery of the shoot apical meristem (SAM). This signal establishes founder cells that build the lateral organ. Primordia initiation is closely associated with the creation of a functional boundary that separates the newly formed primordium from the remainder of the meristem. In the June issue of Plant Cell, we have characterised the JLO (for Jagged Lateral Organ) gene of Arabidopsis, a member of the Lateral Organ boundary Domain gene family. JLO is expressed in boundaries and regulates both auxin transport, via a negative regulation of PIN auxin export carriers, and meristem fate by promoting the expression of the KNOX genes SHOOTMERISTEMLESS (STM) and BP/KNAT1. In this Addendum, we discuss the regulation of PIN genes by JLO, and propose a model for JLO function during embryonic and post-embryonic development.