15th International Conference on Arabidopsis Research - TAIR

T01-045
Characterization of TSF, a homolog of floral pathway
integrator FT
Ayako Yamaguchi(1), Yasushi Kobayashi(1), Sumiko Yamamoto(2), Mitsutomo
Abe(1, 3), Takashi Araki(1, 2)
1-Department of Botany, Graduate School of Science, Kyoto University
2-CREST, Japan Science and Technology Agency
3-Bio-oriented Technology Research Advancement Institution, Japan
TSF (TWIN SISTER OF FT) is a member of a small gene family in Arabidopsis,
which includes FT. FT plays an important role in determination of flowering
time. Since TSF is the closest homolog of FT in the family, it is likely that
TSF plays a similar role as a floral promoter.
Both in long-day (LD) or short-day (SD) conditions, TSF and FT showed
similar patterns of diurnal oscillation. TSF and FT mRNA levels gradually
increased with time under long day conditions. When SD entrained seedling
were shifted to LD, TSF and FT mRNA were immediately up-regulated.
TSF and FT mRNA levels were decreased in co-2 and other late flowering
mutants, such as fca-1. Upon induction of CO activity, TSF and FT expression
was increased in the presence of cycloheximide. TSF and FT are regulated in
a similar manner, and both are regulatory targets of the photoperiod pathway
via CO. Constitutive overexpression of TSF caused early-flowering. On the
other hand, a T-DNA insertion line with decreased TSF mRNA levels did not
change flowering time under LD. However, a decrease of TSF activity enhanced
the phenotype of loss-of-function allele of FT. These results suggested
that TSF has a role as a floral promoter and that it may act redundantly with
FT in the determination of flowering time.
Survey of selected accessions has revealed natural variations in and near
the TSF locus, which can be classified into several types. Col-0 had a 1-kb
insertion of unknown origin in 3' UTR, which has no obvious effect on expression.
Ws and several accessions had a ca. 5-kb retroelement in 3' UTR and
had greatly reduced levels of expression. Ler and Cvi alleles had a simple
structure without large insertions found in other accessions.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T01-046
Epigenetics of seed development: what is the
significance of imprinting?
Abed Chaudhury(1), Ming Luo(1), Rachel Corvisy(1), Bjorg Sherman(1), WJ
Peacock(1), ES Dennis(1)
1-CSIRO Plant Industry, Canberra, Australia
Recent work from our group and several other groups indicate that epigenetic
processes play an important role in seed development. These processes
include the roles of polycomb genes during endosperm development and
parent of origin specific DNA methylation controlling the size of mature seed.
In order to define these epigenetic processes further and also to find other
genes that control the epigenetic process as well as the genetic processes
that accompany it, we have undertaken in-planta gene expression studies in
endosperm using reporter gene GFP.
A number of gene promoters, from different genomic regions have been
used in these studies. The results suggest that a large part of the maternal
genome might be repressed following pollination with hypomethylated pollen
explaining the rescue of the fis mutation as well as the reduced size of seed
caused by such pollination. We have mapped genomic regions undergoing
hypomethylation-induced changes responsible for the rescue of fis seeds.
A novel model involving imprinting, hypomethylation induced gene repression
and epigenetic rescue of fis class seeds will be described.
T01 Development 1 (Flower, Fertilization, Fruit, Seed)