© Benaki Phytopathological Institute
Abstracts - 16th Hellenic Phytopathological Congress
43
raphy and the importance of citrus to the is-
land, systematic surveys for CTV eradication,
sustainable control measurements and epi-
demiological studies need to be undertak-
en. The observations, materials and meth-
ods presented here may assist all three tasks
at a local and at a national level.
RNA silencing pathways may have a positive effect on
Potato spindle tuber
viroid
infectivity in
Nicotiana benthamiana
E. D
ADAMI
1,2
*, K. K
ATSAROU
1
, A. B
OUTLA
1
*, N. V
RETTOS
1, 2
**, S. T
ZORTZAKAKI
1
, I. K
ARAKASILIOTI
1, 2
and K. K
ALANTIDIS
1,2
1
Institute of Molecular Biology and Biotechnology, Foundation for Research and
Technology-Hellas, P.O. Box 1527, GR-711 10 Heraklion, Crete, Greece.
2
Department
of Biology, University of Crete, Heraklion, Crete, Greece. Current address: *B.A., BSRC
“Alexander Fleming” P.O. Box 74145 GR-166 02, Varkiza, Greece; **V.N., Division of
Neuropathology, Department of Pathology and Laboratory Medicine, University of
Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
The role of RNA silencing during viral infec-
tion in plants is well studied. However, the
role of RNA silencing during viroid infec-
tion still remains elusive.
Potato spindle tu-
ber viroid
(PSTVd) is a naked single strand-
ed RNA (ssRNA) plant pathogen, which does
not encode for any protein. PSTVd infection
leads to the accumulation of abundant vi-
roid small interfering RNAs (vd-siRNAs), the
latter being able to trigger the degradation
of homologous RNA sequences. Yet, PST-
Vd genomic RNA itself seems to be resistant
to siRNA-directed degradation. Sequenc-
ing of PSTVd siRNAs during infection has re-
vealed a hotspot-confined origin, indicating
that the rod shape-like structure of the ma-
ture PSTVd ssRNA, rather than the double
stranded RNA (dsRNA) molecules produced
during its replication, may serve as substrate
for Dicer-like (DCL) enzymes. In order to ex-
amine the role of RNA silencing upon PST-
Vd infection, we produced
Nicotiana bentha-
miana
knock down DCL lines (DCLi lines) by
RNA silencing and then tested PSTVd infec-
tivity in the DCLi background. Our analyses
indicate that PSTVd infectivity is facilitated
by DCL1, DCL3 and DCL4, but seems to be
unaffected by DCL2. In addition, viroid repli-
cation seem also to be influenced in double
DCLs knock down plants leading to differ-
ent theories about their role in its infectivity.
Collectively, our results indicate that specif-
ic RNA silencing pathways may be advanta-
geous for viroid infectivity.
Heterologous RNA silencing suppressor proteins support
Plum pox virus
infection
V.I. M
ALIOGKA
*, M. C
ALVO
, A. C
ARBONELL
, J.A. G
ARCIA
and A. V
ALLI
1
Centro Nacional de Biotecnologia-CSIC, Campus Universidad Autonoma de Madrid,
28049 Madrid, Spain. *Current address: Aristotle University of Thessaloniki, Faculty
of Agriculture, Forestry and Natural Environment, School of Agriculture, Laboratory
of Plant Pathology, GR-541 24 Thessaloniki, Greece
HC-Pro is a multifunctional protein encod-
ed by the genome of potyviruses within the
family
Potyviridae,
which acts as a suppres-
sor of RNA silencing (RSS) in plants. Recent
studies have shown that the HCPro of
Plum
pox virus
(PPV) can successfully be replaced
by the P1b protein of
Cucumber vein yellow-
ing ipomovirus
, an RSS coming from a virus
of the same family which however doesn’t
show any sequence similarity with HC-Pro.
In this study in order to clarify whether the
presence of a specific RSS is necessary for
