Simon S., Petrášek J.
PLANT SCIENCE
180:
454-460,
2011
Klíčová slova:
Auxin, IAA, 4-Cl-IAA, IBA, PAA
Abstrakt:
The versatile functionality and physiological importance of the phytohormone auxin is a major focus
of attention in contemporary plant science. Recent studies have substantially contributed to our understanding
of the molecular mechanisms underlying the physiological role of auxin in plant development.
The mechanism of auxin action includes both fast responses not involving gene expression, possibly
mediated by Auxin Binding Protein 1 (ABP1), and slower responses requiring auxin-regulated gene
expression mediated by F-box proteins. These two mechanisms of action have been described to varying
degrees for the major endogenous auxin indole-3-acetic acid (IAA) and for the synthetic auxins 2,4-
dichlorophenoxyacetic acid (2,4-D) and naphthalene-1-acetic acid (NAA). However, in addition to IAA,
plants synthesize three other compounds that are commonly regarded as “endogenous auxins”, namely,
4-chloroindole-3-acetic acid (4-Cl-IAA), indole-3-butyric acid (IBA) and phenylacetic acid (PAA). Although
a spectrum of auxinic effects has been identified for all these as well as several other endogenous compounds,
weremain largely ignorant ofmanyaspects of their mechanisms of action and the extent to which
they contribute to auxin-regulated plant development. Here, we briefly summarize the action of IBA, 4-
Cl-IAA and PAA, and discuss the extent to which their action overlaps with that of IAA or results from
their metabolic conversions to IAA. Other possible pathways for their action are considered. We present
a scheme for homeostatic regulation of IAA levels that embraces other endogenous auxins in terms of the
described mechanism of auxin action including its receptor and downstream signal transduction events.
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