LIBRO-CONGRESO-CITRUS

S09
Nevertheless our knowledge on its pathogenicity/virulence mechanisms is still very limited. The mitogenactivated
protein kinase (MAPK) cascade is involved in the transduction of a variety of extracellular signals and
the regulation of several developmental processes. In most filamentous fungi, SLT2 MAPK family is involved in
the cell integrity pathway and in many cases is essential for full virulence since it is implicated in sporulation,
surface sensing of germ tubes, host penetration and lesion formation. In this work Penicillium digitatum
SLT2 homologous gene PdSLT2 have been identified and characterized. Analysis of its role in pathogenesis/
virulence was carried out through the generation of gene knock-out mutants with Agrobaterium tumefaciens
mediated transformation (ATMT) and evaluating infection capacity. Expression analysis was conducted by
qRT-PCR. Gene expression was determined in orange fruits during P. digitatum infection, and during growth
of P. digitatum in culture medium PDB of both wild type and null mutants. To our knowledge this is the first
MAPK identified in P. digitatum and in this work we confirm that PdSLT2 is involved in fungal virulence and
the expression patterns of several genes in null mutants revealed which genes are transcriptional regulated
by PdSLT2.
S09O04
Function of PdCrz1, a calcineurin-responsive transcription factor, in Penicillium digitatum in
conidiation, virulence and responses to abiotic stresses
Zhang T., and Li H.Y.
Institute of Biotechnology, Zhejiang University, China. hyli@zju.edu.cn
Calcineurin-responsive zinc finger transcription factor Crz1 regulates many genes involved in fungus growth,
morphogenesis, responses to stresses, resistance to drugs and pathogenicity in their hosts. In the present
study, we characterized an ortholog of Crz1, PdCrz1, in P. digitatum, the most important pathogen of
postharvest citrus. PdCrz1 encodes a protein that shares a high amino acid sequence similarity with Crz1 in
Aspergillus spp. To determine the function(s) of PdCrz1, a gene-disruption mutant was generated using an
Agrobacterium tumefaciens-mediated transformation procedure (ATMT). The PdCrz1 disruption (ΔPdCrz1)
mutant was defective in conidiation, cell wall integrity, and virulence, and is hypersensitivity to stresses
caused by Ca 2 , H 2 O 2 and azole fungicides. Expression of cell wall synthase genes (CHS2, CHS3 and FKS1),
P-type ATPases genes (PMR1 and PMC1) was significantly reduced in the PdCrz1 mutant compared with the
wild type P. digitatum. Calcineurin inhibitors were shown to enhance the effect of imazalil on P. digitatum.
In contrast, activation of the Ca 2 /calmodulin-dependent pathway by Ca 2 alleviated the antifungal activity by
imazalil. These results indicate that PdCrz1 plays important roles in P. digitatum conidation, pathogenicity
and membrane lipid homeostasis. In addition, the study also indicates a synergistic fungicidal activity on
P. digitatum between calcineurin inhibitors and DMI fungicides, implying that specific inhibitors of calcium
signalling pathway could be potentially developed as useful adjuvants of conventional DMIs for the control
of fungal diseases.
S09O05
The Protein O-Mannosyltransferase PMT2 of the citrus-specific postharvest pathogen Penicillium
digitatum is involved in conidiogenesis, virulence and sensitivity to the antifungal peptide PAF26
Harries E., Gandía M., Carmona L., and Marcos J.F.
Instituto de Agroquímica y Tecnología de Alimentos (IATA), Food Science, Spain. jmarcos@iata.csic.es
Our group has demonstrated that genes encoding Protein O-Mannosyl Transferases (PMT) determine the
sensitivity of the yeast Saccharomyces cerevisiae to the short antifungal hexapeptide PAF26. In previous
studies, we had identified the family of PMT genes in the citrus fruit postharvest pathogen Penicillium digitatum
and showed their expression during axenic growth and fruit infection. To study functional significance,
Agrobacterium-mediated transformation (ATMT) was used to: (i) disrupt PdigPMT2, and (ii) overexpress it
under control of the A. nidulans gpdA promoter. The mutant Δpmt2 displayed slow rate of growth and a strong
reduction of conidia production. Interestingly, the growth of Δpmt2 was recovered with osmotic stabilization,
while conidiation was only partially restored. Microscopy observation showed balloon-like swollen cells and
defects in conidiophore formation in the Δpmt2 mycelium. The mutant also showed increased sensitivity to
134 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012