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 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.
Centro de Biociências e Biotecnologia (CBB), Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Rio de Janeiro, Brazil.
Daniel B
DB
Zandonadi
Mirella P
MP
Santos
Leonardo B
LB
Dobbss
Fábio L
FL
Olivares
Luciano P
LP
Canellas
Marla L
ML
Binzel
Anna L
AL
Okorokova-Façanha
Arnoldo R
AR
Façanha
D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D006868:Hydrolysis / Q000187:drug effects; D007210:Indoleacetic Acids / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*; D017494:Proton Pumps / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D003313:Zea mays / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development
D016166:Free Radical Scavengers; D006812:Humic Substances; D007210:Indoleacetic Acids; D017494:Proton Pumps; D009599:Nitroprusside; D009569:Nitric Oxide; D006180:Proton-Translocating ATPases