15th International Conference on Arabidopsis Research - TAIR

T05-009
Is Annexin 1 involved in cellular defense against
oxidative stress in Arabidopsis?
Konopka Dorota(1), Witek Kamil(1), Bandorowicz-Pikula Joanna(2), Pikula
Slawomir(2), Hennig Jacek(1)
1-Institute of Biochemistry and Biophysics PAS, Pawinskiego 5A, 02-106 Warsaw, Polska
2-Nencki Institute of Experimental Biology PAS, Pasteur 3, 02-093 Warsaw, Poland
Oxidative stress is a health-threatening phenomenon resulting from accumulation
of partially reduced oxygen species (reactive oxygen species, ROS) that
are both by-products of normal metabolism and are generated in a consequence
of stress. Annexin 1 (AnnAt1) has been recently identified as a new
player contributing to balance ROS level during oxidative burst (1). Induction
of AnnAt1 expression in Arabidopsis was reported after treatments resulting
in perturbation of cell redox state, i.e. H2O2 and salicylic acid (SA) treatments
(2). Moreover, in heterologous systems, AnnAt1 was able to protect yeast and
mammalian cells from oxidative stress (2, 3). In this context it is interesting to
characterize AnnAt1 role in stress response in homologous system.
In preliminary experiments we found, that expression of AnnAt1 is elevated
after different stimuli leading to elevation of intracellular calcium level. In contrast
to PR1-a gene expression, induction of annexin 1, on the mRNA level,
was limited not only to the infection. Elevated expression of AnnAt1 gene was
also observed after wounding or abscisic acid treatment. So, it seems that
annexin 1 can participate either upstream of jasmonic acid (JA) and salicylic
acid (SA) in signaling pathways as a calcium sensor and/or downstream of
them as a ROS scavenging enzyme. To verify this hypothesis, transgenic
plants over-expressing AnnAt1 gene and plants with mutated AnnAt1 gene
were generated, and their reaction on various stressors is in the progress.
1. Plant Phys. 2001, 126: 1072-84;
2. PNAS 1996, 93: 11268-73
3. Int. J. Bioch. Cell, 2001, 33: 591-602
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T05-010
Testing the infectivity and RNA recombination of
brome mosaic bromovirus on Arabidopsis geneknockout
lines related to RNA interference/PTGS.
Aleksandra Dzianot(1), Jozef J. Bujarski(1, 2)
1-Department of Biological Siences, Northern Illinois University, Dekalb, IL, USA.
2-The Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
Recently we have reported that the expression of a suppressor of RNA
interference/post-transcriptional gene silencing (RNAi/PTGS) facilitated the
infection of brome mosaic bromovirus (BMV) in Arabidopsis thaliana (Dzianott
and Bujarski, Virology 318,482-492, 2004). To further test this phenomenon,
several groups of Arabidopsis lines carrying T-DNA insertional knockouts in
genes related to the RNAi/PTGS pathway were infected with BMV and the
levels of virus accumulation determined. This revealed that most of the
knockouts in RNA polymerase (RdRp) genes as well as in Argonaute-like and
in SGS3 (suppressor of gene silencing) genes increased the levels of BMV
infection, as compared to unmutated Arabidopsis (Col-0). These results
confirmed that interfering with various stages of the RNAi/PTGS pathway
facilitated BMV infection. Currently we are testing other groups of Arabidopsis
lines that are partially or totally deficient in RNAi/PTGS. In contrast, an
unrelated Arabidopsis line carrying a knockout within the gene for eukaryotic
translation initiation factor 3b abolished BMV infection, demonstrating the importance
of this factor for BMV life cycle. We in the process of determination
the extent to which RNAi/PTGS mediates genetic BMV RNA recombination.
The implications of these findings for our understanding of the role of host
factors in virus replication will be discussed.
T05 Interaction with the Environment 2 (Biotic)