LIBRO-CONGRESO-CITRUS

S09O01
Genome sequence of the necrotrophic fungus Penicillium digitatum, the main postharvest
pathogen of citrus
Ballester A.R. 1 , Marcet-Houben M. 2 , de la Fuente B. 1 , Harries E. 1 , Marcos J.F. 1 , Gabaldón T. 2 , and González-Candelas L. 1
1 Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Food Science, Spain; and 2 Center for Genomic Regulation (CRG-UPF),
Comparative Genomics, Spain. lgonzalez@iata.csic.es
Penicillium digitatum is a fungal necrotroph causing Green Mold in citrus fruit during postharvest storage. Despite
its economic importance, the genetic bases of its virulence mechanisms and its high host-specificity remain
unknown. Here we present the genomes of two P. digitatum strains that differ in their antifungal resistance
traits, and their comparison with 28 other Pezizomycotina. The two sequenced genomes are highly similar,
yet important differences include the presence, in the resistant strain, of a unique gene cluster, and mutations
previously shown to confer fungicide resistance. The two strains and one isolated in China have identical
mitochondrial genome sequences, suggesting a recent worldwide expansion of the species. Comparison
with the closely-related but non-phytopathogenic P. chrysogenum, reveals a much smaller gene content in P.
digitatum, consistent with a more specialized lifestyle. Large regions in P. chrysogenum genome, including entire
super-contigs, are absent in P. digitatum, probably as the result of large gene family expansions, rather than
acquisition through horizontal gene transfer. Our analysis of P. digitatum genome suggests a heterothallic sexual
reproduction and reveals the molecular bases behind the inability of this species to assimilate nitrate or to
produce the metabolites patulin and penicillin. Finally, we identify the predicted secretome, which provides a
first approximation to the protein repertoire used during invasive growth.
S09O02
RNA-Seq analysis of yeast antagonist Metschnikowia fructicola during interactions with
Penicillium digitatum and grapefruit peel reveals specific transcriptional responses
Hershkovitz V. 1 , Sela N. 2 , Taha L. 3 , Rafael G. 1 , BenDayan C. 1 , Feygenberg O. 1 , Aly R. 3 , Wisniewski M. 4 , and Droby S. 1
1 The Volcani Center (ARO), Institute of Postharvest and Food Science, Israel; 2 The Volcani Center (ARO), Department of Plant pathology
and weed research, Israel; 3 The Volcani Center, Newe-Yaar Research Center, Department of Plant Pathology and Weed Research, ;
and 4 U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), Appalachian Fruit Research Station, USA.vhershko@
agri.gov.il
The yeast Metschnikowia fructicola is a biological control agent with broad activity against various postharvest
diseases of several fruits. Information about the yeast antagonist mode of action still lacking and largely
rely on non-direct evidence. In this study, we performed transcriptome analysis on M. fructicola following
its interaction with the host (grapefruit) and the pathogen (Penicillium digitatum) using next-generation
sequencing technology for RNA (RNA-Seq). We obtained more than 26 million sequencing reads that
were then assembled into 9674 unigenes and half of these genes had an annotation with matches in the
NCBI database. Assembled sequences were annotated with gene description, gene ontology and clusters
of functional group terms. Differential expression analysis revealed more than 250 genes with specific
expression responses. In the antagonist-pathogen, genes related to transmembrane multidrug transport
and to amino acid metabolism were induced. In antagonist-fruit interaction, expression of genes involved in
oxidative stress, iron homeostasis, zinc homeostasis and lipid metabolism were enhanced. We investigated
the gene expression patterns at the transcript levels in the two types of interactions by quantitative real-time
PCR analysis. The data revealed that genes encoding hydrolytic enzymes glucanase (GLU) and chitinase (CHI),
superoxide dismutase (SOD1) and signal transducing MEK kinase (MEKK) had specific expression pattern. Our
results provide new insight into the biology of interaction between host-antagonist-pathogen interactions.
S09O03
The mitogen-activated protein kinase PdSLT2 of Penicillium digitatum is required for fungal
pathogenesis/virulence during citrus infection.
de Ramón-Carbonell M., and Sánchez-Torres P.
Instituto Valenciano de Investigaciones Agrarias (IVIA), Departamento de Protección Vegetal y Biotecnología, Spain. palomas@ivia.es
Postharvest decay accounts for the most significant losses of postharvest citrus worldwide. Green Mold caused
by Penicillium digitatum is the major responsible of the postharvest decay of citrus in Mediterranean regions.
XII INTERNATIONAL CITRUS CONGRESS 2012 - 133
S09