Brassinosteroids do not undergo long-distance transport in pea. Implications for the regulation of endogenous brassinosteroid levels

• Published in: Plant physiology (Bethesda) Vol. 135; no. 4; pp. 2196 - 2206
• Main Authors: Symons, G.M, Reid, J.B
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.08.2004; American Society of Plant Physiologists
• Subjects: Biological and medical sciences; Biological Transport; Biosynthesis; Brassinosteroids; buds; Development and Hormone Action; Flowers - physiology; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; Gene expression regulation; Growth regulators; Leaf buds; Leaves; Metabolism; Mutagenesis; Peas; physiological transport; Phytosterols - metabolism; Pisum sativum; Pisum sativum - physiology; Plant growth regulators; Plant Leaves - physiology; Plant physiology and development; Plant roots; Plant Shoots - physiology; Plant Stems - physiology; Plant tissues; Plants; roots; shoots; spatial distribution; tissue distribution; Translocation; Brassinosteroid; Leguminosae; Long distance; Growth; Dicotyledones; Pisum sativum; Angiospermae; Homeostasis; Plant growth substance; Spermatophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.043034

It is widely accepted that brassinosteroids (BRs) are important regulators of plant growth and development. However, in comparison to the other classical plant hormones, such as auxin, relatively little is known about BR transport and its potential role in the regulation of endogenous BR levels in plants. Here, we show that end-pathway BRs in pea (Pisum sativum) occur in a wide range of plant tissues, with the greatest accumulation of these substances generally occurring in the young, actively growing tissues, such as the apical bud and young internodes. However, despite the widespread distribution of BRs throughout the plant, we found no evidence of long-distance transport of these substances between different plant tissues. For instance, we show that the maintenance of steady-state BR levels in the stem does not depend on their transport from the apical bud or mature leaves. Similarly, reciprocal grafting between the wild type and the BR-deficient lkb mutants demonstrates that the maintenance of steady-state BR levels in whole shoots and roots does not depend on either basipetal or acropetal transport of BRs between these tissues. Together, with results from 3H-BR feeding studies, these results demonstrate that BRs do not undergo long-distance transport in pea. The widespread distribution of end-pathway BRs and the absence of long-distance BR transport between different plant tissues provide significant insight into the mechanisms that regulate BR homeostasis in plants.