A double-negative feedback loop between miR319c and JAW-TCPs establishes growth pattern in incipient leaf primordia in < i > Arabidopsis thaliana < /i >

by Naveen Shankar, Preethi Sunkara, Utpal Nath The microRNA miR319 and its target JAW-TCP transcription factors regulate the proliferation-to-differentiation transition of leaf pavement cells in diverse plant species. In young Arabidopsis leaf primordia,JAW-TCPs are detected towards the distal region whereas the major mRNA319-encoding geneMIR319C, is expressed at the base. Little is known about how this complementary expression pattern ofMIR319C andJAW-TCPs is generated. Here, we show thatMIR319C is initially expressed uniformly throughout the incipient primordia and is later abruptly down-regulated at the distal region, with concomitant distal appearance ofJAW-TCPs, when leaves grow to ~100 μm long. Loss ofJAW-TCPs causes distal extension of theMIR319C expression domain, whereas ectopic TCP activity restrictsMIR319C more proximally. JAW-TCPs are recruited to and are capable of depositing histone H3K27me3 repressive marks on theMIR319C chromatin.JAW-TCPs fail to repressMIR319C in transgenic seedlings where the TCP-bindingcis-elements onMIR319C are mutated, causing miR319 gain-of-function-like phenotype in the embryonic leaves. Based on these results, we propose a model for growth patterning in leaf primordia whereinMIR319C and JAW-TCPs repress each other and divide the uniformly growing primordia into distal differentiation zone and proximal proliferation domain.
Source: PLoS Genetics - Category: Genetics & Stem Cells Authors: Source Type: research