15th International Conference on Arabidopsis Research - TAIR

T05-071
OsEREBP BINDS TO TATA-BINDING PROTEIN,
THEREBY REPRESSING THE BASAL TRANSCRIPTION
OF GENES
Kim, Yun Ju(1), Kim, Jee Eun(1), Jung, Eui-Hwan(1), Kim, Sang Hee(1), Hwang,
Seon Hee(2), Lee, Jung-Sook(1), Suh, Seok-Cheol(1), Hwang Duk-Ju(1)
1-National Institute of Agricultural Biotechnology,
2-National Institute of Agricultural Biotechnology and Dept. of Microbiology, Kangwon National
University, Chuncheon, Korea,200-701
Many transcription factors such as WRKY, bZIP and ethylene-responsive
element binding protein (EREBP) factors are known to be involved in plant
defence responses. It is clear by now that control of gene expression in eukaryotes
involves repression as well as activation of transcription. OsEREBP
has previously shown to function as transcription activator upon pathogen
infections. However, based on the result of transcription repression assay in
yeast, OsEREBP represses GAL4 enhanced activation. The deletion analysis
of OsEREBP indicates that its repressor domain is located at the N-Terminal
of OsEREBP. There are number of ways in which transcriptional repressors
can function. OsEREBP interacts to basal transcription factors such as
TATA-binding protein and TFIIB, indicating that the mechanistic function of
repression by OsEREBP is through the binding of basal transcription factors
such as an human oncogene, p53. T33A and S66A mutants of OsEREBP
did not interact with the TATA-binding protein and TFIIB, indicating that the
N-terminal domain of OsEREBP is important for its repression activity. To
investigate what kinds of genes can be repressed, microarray experiment
with an OsEREBP RNAi transgenic line was carried out. Interestingly genes
involved in abiotic stress tolerance is upregulated in the OsEREBP knock-out
lines generated by RNAi vector. OsEREBP appears to repress genes involved
in the abiotic stress tolerance. Taken together, the OsEREBP is a novel type
of transcription factor reported so far in plants. This work is partly supported
by the NIAB and ARPC grant to Dr. Duk-Ju Hwang in Korea
T05 Interaction with the Environment 2 (Biotic)
T05-072
Analysis of CIR1-mediated disease resistance in
Arabidopsis
Shane Murray(1), Maryke Carstens(1), Sally-Ann Walford(1), Katherine Denby(1)
1-Department of Molecular and Cell Biology, University of Cape Town, Private Bag Rondebosch,
7700, South Africa
Disease resistance in plants is controlled by a complex signal transduction
network dependent on salicylic acid (SA), jasmonic acid (JA) and ethylene
(ET). To identify further components of this network, the cir1 mutant was previously
identified in Arabidopsis thaliana (Murray et al. 2002). cir1 exhibits
constitutive expression of SA- and JA/ET-dependent genes and constitutive
resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst)
and the oomycete pathogen Peronospora parasitica. The CIR1 gene appears
to be a regulator of disease resistance and we are using global gene profiling
to investigate the specific defence genes conferring resistance to these two
different pathogens.
Mutants exist that disrupt the SA (npr1, nahG), JA (jar1) and ET (ein2) signalling
pathways. Double mutants were constructed containing cir1 and each
of these signalling mutants. cir1:NahG double mutants lost cir1-mediated
resistance to both Pst and P. parasitica. However, cir1:jar1 and cir1:ein2 lost
resistance to Pst but maintained resistance to P. parasitica... These double
mutant phenotypes provide us with an avenue to identify defence genes
required for bacterial resistance versus those required for resistance against
the oomycete pathogen. Presumably, cir1 plants express a range of genes
required for resistance against both pathogens. cir1:NahG plants have lost
essential defence genes, whereas cir1:jar1 and cir1:ein2 plants have lost
genes essential for resistance to Pst but not those essential for resistance to
P. parasitica. We aim to identify these genes by microarray analysis of cir1
and cir1 double mutants.
Initially, Affymetrix Genechip assays (carried out at the GARNet facility) were
used to determine expression of 8000 genes in cir1, cir1:ein2, ein2 and wildtype
plants. These experiments identified 45 genes with a >2-fold increase
in expression in cir1 compared to wild-type. Out of these, two subsets could
be identified: 22 genes up-regulated in cir1 and cir1:ein2 and 23 genes upregulated
in cir1 only. These subsets represent possible disease resistance
genes for P. parasitica and Pst respectively. Interestingly, approximately half
of the genes up-regulated in cir1 encode unknown proteins. Verification of
gene expression patterns via independent reverse Northern blot analysis has
confirmed expression of 7 of these genes. We obtained T-DNA insertion lines
in four of these genes from SALK and are currently investigating disease
resistance in these plants. We are also extending the gene expression
studies of the double mutants using full-genome oligo arrays printed by the
University of Arizona.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin