Cytokinin is required for escape but not release from auxin mediated apical dominance.

Abstract

Auxin produced by an active primary shoot apex is transported down the main stem and inhibits the growth of the axillary buds below it, contributing to apical dominance. Here we use Arabidopsis thaliana cytokinin (CK) biosynthetic and signalling mutants to probe the role of CK in this process. It is well established that bud outgrowth is promoted by CK, and that CK synthesis is inhibited by auxin, leading to the hypothesis that release from apical dominance relies on an increased supply of CK to buds. Our data confirm that decapitation induces the expression of at least one ISOPENTENYLTRANSFERASE (IPT) CK biosynthetic gene in the stem. We further show that transcript abundance of a clade of the CK-responsive type-A Arabidopsis response regulator (ARR) genes increases in buds following CK supply, and that, contrary to their typical action as inhibitors of CK signalling, these genes are required for CK-mediated bud activation. However, analysis of the relevant arr and ipt multiple mutants demonstrates that defects in bud CK response do not affect auxin-mediated bud inhibition, and increased IPT transcript levels are not needed for bud release following decapitation. Instead, our data suggest that CK acts to overcome auxin-mediated bud inhibition, allowing buds to escape apical dominance under favourable conditions, such as high nitrate availability.

• Authors: Dörte Müller, Tanya Waldie, Kaori Miyawaki, Jennifer P C To, Charles W Melnyk, Joseph J Kieber, Tatsuo Kakimoto, Ottoline Leyser
• Journal: The Plant journal : for cell and molecular biology (Plant J) Vol. 82 Issue 5 Pg. 874-86 (Jun 2015) ISSN: 1365-313X [Electronic] England
• PMID: 25904120 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: © 2015 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

Chemical References

• ARR3 protein, Arabidopsis
• Arabidopsis Proteins
• Cytokinins
• Indoleacetic Acids
• Nitrates
• Transcription Factors
• Alkyl and Aryl Transferases
• adenylate isopentenyltransferase

Topics

• Alkyl and Aryl Transferases (genetics, metabolism)
• Arabidopsis (genetics, metabolism)
• Arabidopsis Proteins (genetics)
• Cytokinins (genetics, metabolism)
• Gene Expression Regulation, Plant
• Indoleacetic Acids (metabolism)
• Multigene Family
• Mutation
• Nitrates (metabolism)
• Plant Shoots (growth & development, metabolism)
• Transcription Factors (genetics)