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Abstract

Shoot elongation is a vital process for
plant development and productivity,
in both ecological and economic contexts.
Auxin and bioactive gibberellins
(GAs), such as GA1, play critical roles in
the control of elongation,1-3 along with
environmental and endogenous factors,
including other hormones such as the
brassinosteroids.4,5 The effect of auxins,
such as indole-3-acetic acid (IAA), is at
least in part mediated by its effect on GA
metabolism,6 since auxin upregulates
biosynthesis genes such as GA 3-oxidase
and GA 20-oxidase and downregulates
GA catabolism genes such as GA
2-oxidases, leading to elevated levels of
bioactive GA1.7 In our recent paper,1 we
have provided evidence that this action
of IAA is largely independent of DELLA
proteins, the negative regulators of GA
action,8,9 since the auxin effects are still
present in the DELLA-deficient la cry-s
genotype of pea. This was a crucial issue
to resolve, since like auxin, the DELLAs
also promote GA1 synthesis and inhibit
its deactivation. DELLAs are deactivated
by GA, and thereby mediate a feedback
system by which bioactive GA regulates
its own level.10 However, our recent
results,1 in themselves, do not show the
generality of the auxin-GA relationship
across species and phylogenetic groups
or across different tissue types and
responses. Further, they do not touch on
the ecological benefits of the auxin-GA
interaction. These issues are discussed
below as well as the need for the development
of suitable experimental systems to
allow this process to be examined.

Item Type:	Article
Authors/Creators:	Reid, JB and Davidson, SE and Ross, JJ
Journal or Publication Title:	Plant Signaling & Behavior
ISSN:	1559-2316
DOI / ID Number:	https://doi.org/10.4161/psb.6.3.14352
Additional Information:	Licenced under Creative Commons Attribution-NonCommercial 3.0 Unported (CC BY-NC 3.0)
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