Journal Article

Inhibition of Transdifferentiation into Tracheary Elements by Polar Auxin Transport Inhibitors Through Intracellular Auxin Depletion

Saiko Yoshida, Hideo Kuriyama and Hiroo Fukuda

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 12, pages 2019-2028
Published in print December 2005 | ISSN: 0032-0781
Published online December 2005 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pci217
Inhibition of Transdifferentiation into Tracheary Elements by Polar Auxin Transport Inhibitors Through Intracellular Auxin Depletion

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Polar auxin transport is essential for the formation of continuous vascular strands in the plant body. To understand its mechanism, polar auxin transport inhibitors have often been used. However, the role of auxin in vascular differentiation at the unicellular level has remained elusive. Using a Zinnia elegans cell culture system, in which single mesophyll cells transdifferentiate into tracheary elements (TEs), we demonstrated that auxin transport inhibitors prevented TE differentiation and that high concentrations of 1-naphthaleneacetic acid (NAA) and IAA overcame the repression of TE differentiation. Measurements of NAA accumulation with 3H-labeled NAA in the presence or absence of 1-N-naphthylphthalamic acid (NPA) revealed enhanced NAA accumulation within the cell. In the NPA-treated cells, intracellular free NAA decreased, while its metabolites increased. Therefore, the polar auxin transport inhibitors may prevent auxin efflux and consequently promote NAA accumulation in Zinnia cells. The excess intracellular NAA may also activate NAA metabolism, resulting in a decrease in free NAA levels. This depletion of free NAA may prevent TE differentiation. The decreased auxin activity in NPA-treated cells was confirmed by the fact that the DR5 (a synthetic auxin-inducible promoter)-mediated expression of a reporter protein was suppressed in such cells. Gene expression analysis indicated that NPA suppressed TE differentiation at an early process of transdifferentiation into TEs. Based on these results, the inter-relationship between auxin and vascular cell development at a cellular level is discussed.

Keywords: Auxin metabolism; NAA; Polar auxin transport; Tracheary element differentiation; Zinnia elegans; BA, benzyladenine; CaMV, cauliflower mosaic virus; CFP, cyan fluorescent protein; DMSO, dimethylsulfoxide; DR5, synthetic auxin-inducible promoter; GH3, auxin-inducible promoter of the soybean gh3 gene; HFCA, 9-hydroxyfluorene-9-carboxylic acid; NAA, 1-naphthaleneacetic acid; NLS, nuclear localization signal; NPA, 1-N-naphthylphthalamic acid; TE, tracheary element; TIBA, 2,3,5-triiodobenzoic acid; RT–PCR, reverse transcription–PCR; TLC, thin-layer chromatography; YFP, yellow fluorescent protein

Journal Article.  7015 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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