15th International Conference on Arabidopsis Research - TAIR

T05-033
RepA protein from geminivirus alters cell proliferation
in Arabidopsis thaliana.
Bénédicte Desvoyes(1), Elena Ramirez-Parra(1), Crisanto Gutierrez(1)
1-Centro de Biología Molécular Severo Ochoa, CSIC-UAM, Campus Cantoblanco, 28049 Madrid,
Spain.
Geminiviruses are single stranded DNA viruses able to replicate their genetic
material in non-proliferating cells where DNA replication proteins are absent
or inactive. To overcome this barrier, they induce cellular S phase reentry by
reprogramming host gene expression. It has been shown that the viral protein
RepA interacts with the retinoblastoma protein (RBR) and it is believed that
the induction of a permissive environment for viral replication take place
through the RBR/E2F pathway.
We are currently investigating the role of the wheat dwarf virus (WDV) RepA
protein in such processes. For this purpose, transgenic plants expressing
RepA under the control of an inducible promoter have been generated. In
these plants, we showed that the proliferative activity of the host cells is
modified and that the presence of the viral protein increases the amount of
free E2F able to bind DNA. We also demonstrated that E2F target cell cycle
genes such as CDC6, PCNA, ORC2 and ORC3 are induced. Moreover, the
expression level of these genes are not modified in plants expressing in an
inducible manner a RepA mutant unable to bind RBR.
These data indicate that RepA alone is able to interfere with the RBR/E2F
pathway in vivo inducing G1/S transition and therefore facilitating viral replication
in differentiated tissues.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T05-034
The Arabidopsis csb3 mutant shows enhanced
resistance to biotrophic pathogens
Gil-Morrió, Mª José(1), Jordá, Lucía(2), Mauch-Mani, Brigitte(3), Vera, Pablo(1)
1-Instituto de Biología Molecular y Celular de Plantas. Universidad Politécnica de Valencia. Avda de
los Naranjos s/n 46022-Valencia, Spain
2-Departamento de Biotecnología. ETSI Agrónomos, U.P.M. 28040, Madrid, Spain
3-Department of Biology, University of Fribourg, 3 Route Albert Gockel, CH-1700 Fribourg,
Switzerland
The defense-related P69C gene was previously identified in tomato
plants and shown to be induced during the course of an incompatible
and compatible plant pathogen interaction (1).To determine which components
of the plant defense response make important contributions to
limiting pathogen attack, and M2 mutagenized populations of a transgenic
Arabidopsis line was screened for mutants showing constitutive expression
of &#61538;&#61485;glucoronidase activity driven by the promoter region
of the P69C gene. This screening render the isolation of a recessive mutant
named as constitutive subtilisin3 (csb3). csb3 shows enhanced resistance to
the biotrophic pathogens Pseudomonas syringae and Peronospora parasitica,
and exhibits normal susceptibility to Plectospharella and the necrotrophic
pathogen Botrytis cinerea. This csb3 resistance to biotrophic pathogen is associated
with synthesis and accumulation of SA and constitutive expression
of some PR genes. Moreover, csb3 shows spontaneous formation of microHR-like
lesions in the absence of pathogen. We generated double mutants
between csb3 and previous described SA-dependent signalling mutants to
analyse the implication of the SA pathway in csb3 phenotype. These double
mutants suggest that the characteristic resistance of csb3 to biotrophic pathogens
is channel through the salycilic-acid and NPR1 pathway. Furthermore,
we show evidences suggesting that CSB3 may link SA not only to defense
but also to development
(1) Jordá, L. y Vera, P. (2000) Plant Physiol.124, 1049-1058
T05 Interaction with the Environment 2 (Biotic)