Nitric oxide mediates humic acids-induced root development and plasma membrane H+-ATPase activation |
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Authors: | Daniel B Zandonadi Mirella P Santos Leonardo B Dobbss Fábio L Olivares Luciano P Canellas Marla L Binzel Anna L Okorokova-Façanha Arnoldo R Façanha |
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Institution: | 1. Centro de Biociências e Biotecnologia (CBB), Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil 2. Centro de Ciências e Tecnologias Agropecuárias (CCTA), UENF, Rio de Janeiro, Brazil 3. Texas AgriLife Research, 17360 Coit Road, Dallas, TX, 75252, USA
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Abstract: | 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. |
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