15th International Conference on Arabidopsis Research - TAIR

T04-073
CHARACTERIZATION OF COL3, A POSITIVE
REGULATOR OF LIGHT SIGNALING.
Sourav Datta(1), Xing-Wang Deng(2), Magnus Holm(1)
1-CMB, Gothenburg University, Sweden
2-MCDB, Yale University, CT, USA
Arabidopsis COP1 acts to repress photomorphogenesis in the absence of
light.
It has previously been shown that COP1 directly interacts with the bZIP transcription
factors HY5, HYH and LAF1 in the dark, and promotes the proteasome-mediated
degradation of these positive regulators of photomorphogenesis,.
Here we identify a physical and genetic interaction between COP1 and
COL3. COL3 was identified in a yeast two hybrid screen for COP1 interacting
proteins and we have mapped the interaction to the WD40 domain in COP1
and a conserved valine-proline pair in the C-terminus of COL3. GFP fused
COL3 protein gives a diffuse nuclear fluorescence in onion cells. However,
when expressed together with COP1, COL3 co-localizes with COP1 in distinct
nuclear speckles suggesting that the two proteins interact also in living plant
cells. We identified a T-DNA insertion in the COL3 gene that results in loss of
detectable COL3 mRNA. Plants carrying insertions in the COL3 gene display
decreased blue light sensitivity and the col3 mutation can suppress cop1
mutations. These findings suggest that COL3 act as a positive regulator of
light signaling and provides genetic support for an interaction between COL3
and COP1. col3 plants flower early, opposite to co but similar to hy5 and hyh.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T04-074
Characterization of a novel, RCD1-related gene
family
Tiina Kuusela(1), Jaakko Kangasjärvi(1)
1-Plant Biology, Department of Biological and Environmental Sciences, University of Helsinki, POB
56 (Viikinkaari 9), FIN-00014 Helsinki, Finland
Stress-induced plant hormones and reactive oxygen species (ROS) interact
in a complicated manner during the regulation of programmed cell death
(PCD). The rcd1 (radical-induced cell death1) mutant has been shown to
be defective in the containment of PCD and in the signalling of ethylene,
jasmonic acid and abscisic acid. The rcd1-1 mutation results in mis-spliced
transcripts of At1g32230. Here we show that T-DNA interrupting RCD1 yields
rcd1 phenotype, which further suggests that rcd1 is a lack-of-function mutant.
The RCD1 function is yet unknown, but according to a yeast two-hybrid
analysis, it may include interactions with several stress-related transcription
factors. RCD1 belongs to a putative novel gene family with 5 unknown genes
encoding proteins distinctively similar to RCD1 (SRO1-SRO5; SIMILAR TO
RCD-ONE 1-5). A genome duplication event connects RCD1 to SRO1, SRO2
to SRO3 and SRO4 to SRO5, after which all except SRO3 have remained as
expressed genes. Both RCD1 and SRO1 have nuclear localization signals
and a WWE-protein-protein interaction domain implicated to ubiquitination
and ADP-ribose conjugation systems. These conserved domains are lacking
from SRO2-SRO5. However, RCD1 and all SROs possess ADP-ribosylation
domains, which assigns them to the same superfamily as for instance
poly(ADP-ribose)polymerases (PARP)s. The promoter regions of RCD1 and
SRO genes contain several transcription factor-binding sites, for instance
cis-acting elements involved in abscisic acid, salicylic acid, defence and
stress responses as well as light responsive elements. However, the promoter
structures within the RCD1-SRO gene family vary indicating that they may
response differently to environmental stimuli. The putative function of the
RCD1-SRO proteins is discussed in respect to the latest results obtained from
a system biology approach chosen for their characterization.
T04 Interaction with the Environment 1 (Abiotic)