Control of Jasmonate Biosynthesis and Senescence by miR319 Targets

Carla Schommer,Javier F Palatnik,Pooja Aggarwal,Aurore Chételat,Utpal Nath,Edward E Farmer,Pilar Cubas,Detlef Weigel,James C Carrington

doi:10.1371/journal.pbio.0060230

Abstract

Considerable progress has been made in identifying the targets of plant microRNAs, many of which regulate the stability or translation of mRNAs that encode transcription factors involved in development. In most cases, it is unknown, however, which immediate transcriptional targets mediate downstream effects of the microRNA-regulated transcription factors. We identified a new process controlled by the miR319-regulated clade of TCP (TEOSINTE BRANCHED/CYCLOIDEA/PCF) transcription factor genes. In contrast to other miRNA targets, several of which modulate hormone responses, TCPs control biosynthesis of the hormone jasmonic acid. Furthermore, we demonstrate a previously unrecognized effect of TCPs on leaf senescence, a process in which jasmonic acid has been proposed to be a critical regulator. We propose that miR319-controlled TCP transcription factors coordinate two sequential processes in leaf development: leaf growth, which they negatively regulate, and leaf senescence, which they positively regulate.

Highlights

In plants, microRNAs regulate target genes through miRNA-guided cleavage or translational repression of mRNAs that have highly complementary motifs to the regulatory miRNA
We investigated the downstream events regulated by five TCP (TEOSINTE BRANCHED/CYCLOIDEA/PCF) transcription factors that are controlled by the microRNA miR319 in Arabidopsis thaliana
We propose that the miR319-regulated TCP factors coordinate different aspects of leaf development and physiology: growth, which they negatively regulate, and aging, which they positively regulate

Summary

Introduction

MicroRNAs (miRNAs) regulate target genes through miRNA-guided cleavage or translational repression of mRNAs that have highly complementary motifs to the regulatory miRNA. Translational repression may be more widespread than previously thought by those not familiar with the field [4], much of the available evidence suggests that the sequence requirements for regulation by mRNA cleavage and translational repression are very similar [5,6,7]. Even closely related miRNAs can have a unique spectrum of target genes, without evidence for crossregulation at the level of mRNA cleavage or translational repression [8]. One of the few exceptions appears to be an engineered mutation in a microRNA 398 (miR398) target gene that prevents efficient mRNA cleavage but still allows translational repression [9]

Results

Discussion

Conclusion