15th International Conference on Arabidopsis Research - TAIR

T01-101
Interaction of Polycomb-group proteins controlling
flowering in Arabidopsis
Yindee Chanvivattana(2), Anthony Bishopp(1), Daniel Schubert(1), Christine
Stock(1), Yong Hwan Moon(3), Renee Sung(3), Justin Goodrich(1)
1-Institute of Cell and Molecular Biology, The King’s Buildings, Mayfield Road, Edinburgh EH9 3JH
2-Current address: National Center for Genetic Engineering and Biotechnology Thailand Science
Park 113, Phahonyothin Rd., Klong 1, Klong Luang, Pathum Thani 12120 Thailand.
3-Department of Plant and Microbial Biology, University of California, Berkeley, California 94720,
USA
The Drosophila Polycomb-group genes Suppressor of zeste12 (Su[z]12) and
Enhancer of zeste (E[z]) genes encode two components of a protein complex
involved in histone methylation. In Arabidopsis, each is represented by a
small gene family. The Su(z)12 family has three members, FERTILISATION
INDEPENDENT SEED2 (FIS2), EMBRYONIC FLOWER2 (EMF2), and VERNALI-
SATION2 (VRN2). The three genes have distinct developmental roles in seed
development, flowering time control and vernalization response, respectively.
The E(z) family also has three members: MEDEA (MEA) which has a similar
function to FIS2; CURLY LEAF (CLF) which, like EMF2, represses flowering;
and a poorly characterised third member, SWINGER (SWN) (also known as
EZA1). We show that these similarities reflect interactions between the plant
E(z) and Su(z)12 class proteins. The interactions are mediated by two novel
domains that are conserved between the plant and animal proteins. Yeast
two-hybrid studies also show that the CLF and SWN proteins can interact
with VRN2, suggesting that they may also mediate the vernalization response.
Characterisation of SWN reveals that it acts redundantly with CLF, and therefore
that CLF has a broader developmental function than was evident from
analysis of single mutant phenotypes. Mis-expression studies indicate that
MEA has diverged from CLF and SWN both in expression pattern and protein
function. We suggest that the plant Pc-G proteins form at least three complexes
with discrete developmental roles. These complexes are likely similar
to the animal PRC2 with respect to composition and biochemical function,
but have diverged with respect to target gene specificity.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T01-102
Isolation of novel mutants defective in pollen tube
growth
Ulrich Klahre(1), Benedikt Kost(1)
1-Heidelberg Institut fuer Pflanzenwissenschaften
We have generated more than 2000 T-DNA transformed Arabidopsis lines
which carry a Basta resistance cassette and a GUS-GFP marker driven by the
pollen specific LAT52 promoter. In a first round we have screened the primary
transformants for abnormal segregation to identify mutations in genes
that lead to gametophytic deficiencies. In a second round we have used the
expression of the GUS-GFP protein in mutant pollen to select tagged lines
that show specific defects in pollen growth.
Using this screen we have so far isolated two lines that show interesting
defects in pollen growth. Line A segregates at a ratio of approximately
1:1.5 and pollen can still grow, albeit to a decreased length, and they can
lead to fertilisation in relatively few cases. We have identified a T-DNA insert
in a gene encoding a subunit of the 26S proteasome.
A second line (Line B) segregates at a ratio of 1:1 indicating that
no fertilisation occurs by mutant pollen. The pollen tubes stained for GUS do
not penetrate the style in vivo and show very poor growth in vitro. A T-DNA
insertion was identified in the GAD2 gene which encodes a protein involved
in the g-amino butyric acid (GABA) biosynthesis pathway. In vitro experiments
show that tube growth can not be rescued by the exogenous addition of
GABA.
T01 Development 1 (Flower, Fertilization, Fruit, Seed)