microRNA‐directed cleavage of ATHB15 mRNA regulates vascular development in Arabidopsis inflorescence stems

Abstract

SummaryClass III homeodomain-leucine zipper proteins regulate critical aspects of plant development, including lateral organ polarity, apical and lateral meristem formation, and vascular development. ATHB15, a member of this transcription factor family, is exclusively expressed in vascular tissues. Recently, a microRNA (miRNA) binding sequence has been identified in ATHB15 mRNA, suggesting that a molecular mechanism governed by miRNA binding may direct vascular development through ATHB15. Here, we show that miR166-mediated ATHB15 mRNA cleavage is a principal mechanism for the regulation of vascular development. In a gain-of-function MIR166a mutant, the decreased transcript level of ATHB15 was accompanied by an altered vascular system with expanded xylem tissue and interfascicular region, indicative of accelerated vascular cell differentiation from cambial/procambial cells. A similar phenotype was observed in Arabidopsis plants with reduced ATHB15 expression but reversed in transgenic plants overexpressing an miR166-resistant ATHB15. ATHB15 mRNA cleavage occurred in standard wheat germ extracts and in Arabidopsis and was mediated by miR166 in Nicotiana benthamiana cells. miR166-assisted ATHB15 repression is likely to be a conserved mechanism that regulates vascular development in all vascular plants.

tRNA-dependent cleavage of the ColE1 plasmid-encoded RNA I

“…In many cases, RNA-mediated RNA cleavage also requires the assistance of specific proteins. Examples are the activities of siRNA and microRNAs (Zhang et al, 2002;Doi et al, 2003;Zeng et Goodman, 2004; Yekta et al, 2004;Kim et al, 2005b;Behlke, 2006;Ronemus et al, 2006;Valencia-Sanchez et al, 2006). Nevertheless, other reports have described reactions of direct RNA-mediated cleavage of RNA (Tanner, 1999;Lilley, 1999;Doudna & Cech, 2002;Sago et al, 2004).…”

Identification of Potential microRNAs and Their Targets in Brassica rapa L.

“…Northern blot analyses Total RNA was isolated from, 20-day-old B. rapa cultivar Kenshin seedling plants by using Trizol reagent (Invitrogen, USA) according to the procedure previously described by Kim et al (2005). Total RNA was separated in 15% urea-polyacrylamide gel and electrically transferred to Hybond-N+ membranes (Amersham Bioscience, UK).…”

Organ Polarity in Plants Is Specified through the Opposing Activity of Two Distinct Small Regulatory RNAs

“…Dominant gain-of-function miRNA mutants, however, are more common and have revealed developmental roles for several miRNAs. For example, the meristem enlarged1 and jabba1-D mutants both develop fasciated stems and enlarged meristems resulting from altered MIR166a and MIR166g expression, respectively (Kim et al 2005;Williams et al 2005b). Similar gain-of-function mutations for miR156, miR159, miR160, miR164, miR172, and miR319 lead to defects in vegetative and floral organ development, meristem function, and flowering (see Jones- Rhoades et al 2006).…”