Nitric oxide mediates humic acids-induced root development and plasma membrane H⁺-ATPase activation

It is widely reported that some humic substances behave as exogenous auxins influencing root growth by mechanisms that are not yet completely understood. This study explores the hypothesis that the humic acids' effects on root development involve a nitric oxide signaling. Maize seedlings were t...

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Bibliographic Details
Published in:Planta 2010-04, Vol.231 (5), p.1025-1036
Main Authors: Zandonadi, Daniel B, Santos, Mirella P, Dobbss, Leonardo B, Olivares, Fábio L, Canellas, Luciano P, Binzel, Marla L, Okorokova-Façanha, Anna L, Façanha, Arnoldo R
Format: Article
Language:English
Subjects:
Agriculture
Auxins
Biological and medical sciences
Biomedical and Life Sciences
Cell Membrane - drug effects
Cell Membrane - enzymology
Cell membranes
Corn
Ecology
Enzyme Activation - drug effects
Fluorescence
Forestry
Free Radical Scavengers - pharmacology
Fundamental and applied biological sciences. Psychology
Humic Substances
Hydrogen-Ion Concentration - drug effects
Hydrolysis - drug effects
Indoleacetic Acids - pharmacology
Life Sciences
Nitric Oxide - biosynthesis
Nitric Oxide - pharmacology
Nitroprusside - pharmacology
Original Article
Oxides
Plant roots
Plant Roots - cytology
Plant Roots - drug effects
Plant Roots - growth & development
Plant Sciences
Plants
Proton Pumps - metabolism
Proton-Translocating ATPases - metabolism
Root growth
Seedlings
Zea mays - cytology
Zea mays - drug effects
Zea mays - enzymology
Zea mays - growth & development
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Summary:It is widely reported that some humic substances behave as exogenous auxins influencing root growth by mechanisms that are not yet completely understood. This study explores the hypothesis that the humic acids' effects on root development involve a nitric oxide signaling. Maize seedlings were treated with HA 20 mg C L⁻¹, IAA 0.1 nM, and NO donors (SNP or GSNO), in combination with either the auxin-signaling inhibitor PCIB, the auxin efflux inhibitor TIBA, or the NO scavenger PTIO. H⁺-transport-competent plasma membrane vesicles were isolated from roots to investigate a possible link between NO-induced H⁺-pump and HA bioactivity. Plants treated with either HA or SNP stimulated similarly the lateral roots emergence even in the presence of the auxin inhibitors, whereas NO scavenger diminished this effect. These treatments induced H⁺-ATPase stimulation by threefold, which was abolished by PTIO and decreased by auxin inhibitors. HA-induced NO synthesis was also detected in the sites of lateral roots emergence. These data depict a new scenario where the root development stimulation and the H⁺-ATPase activation elicited by either HA or exogenous IAA depend essentially on mechanisms that use NO as a messenger induced site-specifically in the early stages of lateral root development.
ISSN:0032-0935
1432-2048
DOI:10.1007/s00425-010-1106-0