Project description:Blue mold, caused by Penicillium expansum, is responsible for postharvest losses of apple fruit, and threatens human health through production of the potent mycotoxin patulin. No major gene(s) providing resistance have as yet been identified, but recent studies indicate a quantitative control of the disease. An AryANE chip covering 60K apple transcripts was used to identify possible candidate gene(s) that are differentially regulated between resistant and susceptible cultivars upon P. expansum infection. Induction of cell wall related gene (PGIP1), and three genes involved in the ‘down-stream’ flavonoid biosynthesis pathway (CHS, FLS and LDOX), shows the fundamental role of cell wall as an important barrier, and contents of polyphenolic compounds of fruits as a quantitative components in enhancing disease resistance to blue mold. Moreover, exogenous application of Jasmonic acid hormone enhanced the defense mechanism in fruits. This is the first report linking Jasmonic acid and activation of cell wall and flavonoid pathway genes in apple fruit resistance to blue mold. Results provide an initial categorization of genes that are potentially involved in the resistance mechanism, and should be useful for developing tools for gene marker-assisted breeding of apple cultivars with an improved resistance to blue mold. SUBMITTER_CITATION: Ahmadi-Afzadi, M., Orsel Baldwin, M., Pelletier, S., Cournol, M., Proux-Wéra, E., Nybom, H., Renou, J.-P. (2018). Genome-wide expression analysis suggests a role for jasmonates in the resistance to blue mold in apple. Plant Growth Regulation, 85 (3), 375-387. , DOI : 10.1007/s10725-018-0388-2
Project description:The soft rot pathogen Janthinobacterium agaricidamnosum causes devastating damage to button mushrooms (Agaricus bisporus), one of the most cultivated and commercially relevant mushrooms. We previously discovered that this pathogen releases the membrane-disrupting lipopeptide jagaricin. This bacterial toxin, however, could not solely explain the rapid decay of mushroom fruiting bodies, indicating that J. agaricidamnosum implements a more sophisticated infection strategy. In this study, we show that secretion systems play a crucial role in soft rot disease. By mining the genome of J. agaricidamnosum, we identified gene clusters encoding a type I (T1SS), a type II (T2SS), a type III (T3SS), and two type VI secretion systems (T6SS). Through a combination of knockout studies and bioassays, we found that the T2SS and T3SS of J. agaricidamnosum are required for soft rot disease. Furthermore, comparative secretome analysis and activity-guided fractionation identified a number of secreted lytic enzymes responsible for mushroom damage. Our findings regarding the contribution of secretion systems to the disease process expand the current knowledge of bacterial soft rot pathogens and represent a significant stride towards identifying targets for their disarmament with secretion system inhibitors.
Project description:Bull’s eye rot is one of the most severe diseases that may affect apples during storage. It is caused by the fungus Neofabraea vagabunda, and the mechanism by which the pathogen infects the fruits is only partially understood. In particular, very little is known about the molecular mechanisms regulating the interaction between the pathogen and the host during symptoms development. Despite different apple cultivars show different levels of resistance to the pathogen, the genetic basis of these responses are unknown. In order to understand the molecular mechanisms occurring in the apple fruit during N. vagabunda infection, a large-scale transcriptome study by RNA-Seq analysis was performed, comparing fruits of the sensitive ‘Roho’ cultivar and the resistant cultivar ‘Ariane’ after artificial infection with N. vagabunda and a storage period of 4 months.
Project description:P. expansum is regarded as one of the most important postharvest rots of apple fruit and is also of great concern to fruit processing industries. Elucidating the pathogenicity mechanism of this pathogen is of utmost importance for the development of effective and safe management strategies. Although, many studies on modification of the host environment by the pathogen were done, its interactions with fruit during the early stages of infection and the virulence factors that mediate pathogenicity have not been fully defined. Effectors carrying LysM domain have been identified in numerous pathogenic fungi and their role in the first stages of infection has been established. In this study, we identified 18 LysM genes in the P. expansum genome. Amino acid sequence analysis indicated that P. expansum LysM proteins belong to a clade of fungal-specific LysM. Eleven of the discovered LysM genes were found to have secretory pathway signal peptide, among them, 4 (PeLysM1 PeLysM2, PeLysM3 and PeLysM4) were found to be highly expressed during the infection and development of decay of apple fruit. Effect of targeted deletion of the four putative PeLysM effectors on the growth and pathogenicity was studied. Possible interactions of PeLysM with host proteins was investigated using the yeast-two-hybrid system.
Project description:Penicillium digitatum and Penicillium expansum are two closely related fungal plant pathogens causing green and blue mold in harvested fruit, respectively. The two species differ in their host specificity, being P. digitatum restricted to citrus fruits and P. expansum able to infect a wide range of fruits after harvest. Although host-specific Penicillium species have been found to have a smaller gene content, it is so far unclear whether these different host specificities impact genome variation at the intraspecific level. Here we assessed genome variation across four P. digitatum and seven P. expansum isolates from geographically distant regions. Our results show very high similarity (average 0.06 SNPs [single nucleotide polymorphism] per kb) between globally distributed isolates of P. digitatum pointing to a recent expansion of a single lineage. This low level of genetic variation found in our samples contrasts with the higher genetic variability observed in the similarly distributed P. expansum isolates (2.44 SNPs per kb). Patterns of polymorphism in P. expansum indicate that recombination exists between genetically diverged strains. Consistent with the existence of sexual recombination and heterothallism, which was unknown for this species, we identified the two alternative mating types in different P. expansum isolates. Patterns of polymorphism in P. digitatum indicate a recent clonal population expansion of a single lineage that has reached worldwide distribution. We suggest that the contrasting patterns of genomic variation between the two species reflect underlying differences in population dynamics related with host specificities and related agricultural practices. It should be noted, however, that this results should be confirmed with a larger sampling of strains, as new strains may broaden the diversity so far found in P. digitatum.
Project description:The pine weevil Hylobius abietis (L.) is a severe pest of conifer seedlings in reforested areas of Europe and Asia. To identify minimally toxic and ecologically sustainable compounds for protecting newly planted seedlings, we evaluated the volatile metabolites produced by microbes isolated from H. abietis feces and frass. Female weevils deposit feces and chew bark at oviposition sites, presumably thus protecting eggs from feeding conspecifics. We hypothesize that microbes present in feces/frass are responsible for producing compounds that deter weevils. Here, we describe the isolation of a fungus from feces and frass of H. abietis and the biological activity of its volatile metabolites. The fungus was identified by morphological and molecular methods as Penicillium expansum Link ex. Thom. It was cultured on sterilized H. abietis frass medium in glass flasks, and volatiles were collected by SPME and analyzed by GC-MS. The major volatiles of the fungus were styrene and 3-methylanisole. The nutrient conditions for maximum production of styrene and 3-methylanisole were examined. Large quantities of styrene were produced when the fungus was cultured on grated pine bark with yeast extract. In a multi-choice arena test, styrene significantly reduced male and female pine weevils' attraction to cut pieces of Scots pine twigs, whereas 3-methylanisole only reduced male weevil attraction to pine twigs. These studies suggest that metabolites produced by microbes may be useful as compounds for controlling insects, and could serve as sustainable alternatives to synthetic insecticides.