MIR319Cand its targetJAW-TCPs repress each other and establish cell proliferation pattern in incipient leaf primordia inArabidopsis thaliana

Abstract

AbstractThe microRNA miR319 and its target JAW-TCP transcription factors regulate leaf morphogenesis in diverse plant species. In young Arabidopsis leaf primordia,JAW-TCPs are detected towards the distal region whereasMIR319Cis expressed at the base. Little is known about how this complementary expression pattern ofMIR319CandJAW-TCPsis generated. Here, we show thatMIR319Cis 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-TCPscauses distal extension ofMIR319Cexpression domain, whereas ectopic TCP activity restrictsMIR319Cmore proximally. JAW-TCPs are recruited to and are capable of depositing histone H3K27me3 repressive marks on theMIR319Cchromatin.JAW-TCPs fail to repressMIR319Cin transgenic seedlings where the TCP-bindingcis-elements onMIR319Care mutated, causing miR319 gain-of-function-like phenotype. Based on these results, we propose a model for growth patterning in leaf primordia whereinMIR319Cand JAW-TCPs repress each other and divide the uniformly growing primordia into distal differentiation zone and proximal proliferation domain.Summary statementJAW-TCPstranscriptionally repress the microRNA319 encoding geneMIR319Cto generate their mutually exclusive expression pattern and establish growth polarity during early stages of Arabidopsis leaf primordia.