Indole-3-butyric acid promotes adventitious rooting in Arabidopsis thaliana thin cell layers by conversion into indole-3-acetic acid and stimulation of anthranilate synthase activityReport as inadecuate




Indole-3-butyric acid promotes adventitious rooting in Arabidopsis thaliana thin cell layers by conversion into indole-3-acetic acid and stimulation of anthranilate synthase activity - Download this document for free, or read online. Document in PDF available to download.

BMC Plant Biology

, 17:121

Development and cell biology

Abstract

BackgroundIndole-3-acetic acid IAA, and its precursor indole-3-butyric acid IBA, control adventitious root AR formation in planta. Adventitious roots are also crucial for propagation via cuttings. However, IBA roles is-are still far to be elucidated. In Arabidopsis thaliana stem cuttings, 10 μM IBA is more AR-inductive than 10 μM IAA, and, in thin cell layers TCLs, IBA induces ARs when combined with 0.1 μM kinetin Kin. It is unknown whether arabidopsis TCLs produce ARs under IBA alone 10 μM or IAA alone 10 μM, and whether they contain endogenous IAA-IBA at culture onset, possibly interfering with the exogenous IBA-IAA input. Moreover, it is unknown whether an IBA-to-IAA conversion is active in TCLs, and positively affects AR formation, possibly through the activity of the nitric oxide NO deriving from the conversion process.

ResultsRevealed undetectable levels of both auxins at culture onset, showing that arabidopsis TCLs were optimal for investigating AR-formation under the total control of exogenous auxins. The AR-response of TCLs from various ecotypes, transgenic lines and knockout mutants was analyzed under different treatments. It was shown that ARs are better induced by IBA than IAA and IBA + Kin. IBA induced IAA-efflux PIN1 and IAA-influx AUX1-LAX3 genes, IAA-influx carriers activities, and expression of ANTHRANILATE SYNTHASE -alpha1 ASA1, a gene involved in IAA-biosynthesis. ASA1 and ANTHRANILATE SYNTHASE -beta1 ASB1, the other subunit of the same enzyme, positively affected AR-formation in the presence of exogenous IBA, because the AR-response in the TCLs of their mutant wei2wei7 was highly reduced. The AR-response of IBA-treated TCLs from ech2ibr10 mutant, blocked into IBA-to-IAA-conversion, was also strongly reduced. Nitric oxide, an IAA downstream signal and a by-product of IBA-to-IAA conversion, was early detected in IAA- and IBA-treated TCLs, but at higher levels in the latter explants.

ConclusionsAltogether, results showed that IBA induced AR-formation by conversion into IAA involving NO activity, and by a positive action on IAA-transport and ASA1-ASB1-mediated IAA-biosynthesis. Results are important for applications aimed to overcome rooting recalcitrance in species of economic value, but mainly for helping to understand IBA involvement in the natural process of adventitious rooting.

KeywordsAdventitious roots Anthranilate synthase genes ech2ibr10 mutant Indole-3-butyric acid Indole-3-acetic acid Indole-3-acetic acid influx carriers Indole-3-acetic acid efflux carriers In vitro culture Nitric oxide Stem thin cell layers AbbreviationsAOSAllene Oxide Synthase

ARAdventitious root

ARFAuxin response factor

ASA1ANTHRANILATE SYNTHASE-alpha1

ASBANTHRANILATE SYNTHASE-beta1

AUX1AUXIN RESISTANT1

ECH2ENOYL-COAHYDRATASE2

HFHormone free

IAAIndole-3-acetic acid

IBAIndole-3-butyric acid

IBR10INDOLE-3-BUTYRIC ACID RESPONSE10

JAJasmonic acid

KinKinetin

LAX3LIKE AUXIN RESISTANT3

LOX2Lypoxygenase 2

LRLateral root

MeJAMethyl jasmonate

NONitric oxide

PIN1PIN-FORMED1

PRPrimary root

TCLsThin cell layers

WEI2WEAK ETHYLENE-INSENSITIVE2

WEI7WEAK ETHYLENE-INSENSITIVE7

WTWild type

Electronic supplementary materialThe online version of this article doi:10.1186-s12870-017-1071-x contains supplementary material, which is available to authorized users.

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Author: L. Fattorini - A. Veloccia - F. Della Rovere - S. D’Angeli - G. Falasca - M. M. Altamura

Source: https://link.springer.com/







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