Articles > Discrete and Essential Roles of the Multiple Domains of Arabidopsis FHY3 in Mediating Phytochrome A Signal Transduction

Discrete and Essential Roles of the Multiple Domains of Arabidopsis FHY3 in Mediating Phytochrome A Signal Transduction

Abstract: Phytochrome A (phyA) is the primary photoreceptor for mediating various
far-red light induced responses in higher plants. We recently showed
that Arabidopsis FHY3 and FAR1, a pair of homologous proteins sharing
significant sequence homology to Mutator-like transposases, act as
novel transcription factors essential for activating the expression of
FHY1 and FHL, whose products are required for light-induced phyA
nuclear accumulation and subsequent light responses. FHY3, FAR1 and
Mutator-like transposases also share a similar domain structure,
including an N-terminal C2H2 zinc-finger domain, a central putative
core transposase domain, and a C-terminal SWIM motif. In this study, we
performed a promoter-swapping analysis of FHY3 and FAR1. Our results
suggest that the partially overlapping function of FHY3 and FAR1
entails divergence of their promoter activities and protein
sub-functionalization. To gain a better understanding of the molecular
mode of FHY3 function, we performed a structure-function analysis,
using site-directed mutagenesis and transgenic approaches. We show that
the conserved N-terminal C2H2 zinc-finger domain is essential for
direct DNA binding and biological function of FHY3 in mediating light
signaling, whereas the central core transposase domain and C-terminal
SWIM domain are essential for the transcriptional regulatory activity
of FHY3 and its homodimerization or hetero-dimerization with FAR1.
Further, the ability to form homo- or hetero-dimers largely correlates
with the transcriptional regulatory activity of FHY3 in plant cells.
Together, our results reveal discrete roles of the multiple domains of
FHY3 and provide functional support for the proposition that FHY3 and
FAR1 represent transcription factors derived from a Mutator-like
transposase(s).

Full access to article in Plant Physiol. 2008 Aug 20.


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