New insights into the evolution of host specificity of three Penicillium species and the pathogenicity of P. Italicum involving the infection of Valencia orange (Citrus sinensis)

Abstract

Blue and green molds, the common phenotypes of post-harvest diseases in fruits, are mainly caused by Penicillium fungal species, including P. italicum, P. digitatum, and P. expansum . We sequenced and assembled the genome of a P. italicum strain, which contains 31,034,623 bp with 361 scaffolds and 627 contigs. The mechanisms underlying the evolution of host specificity among the analyzed Penicillium species were associated with the expansion of protein families, genome restructuring, horizontal gene transfer, and positive selection pressure. A dual-transcriptome analysis following the infection of Valencia orange (Citrus sinensis) by P. italicum resulted in the annotation of 9,307 P. italicum genes and 24,591 Valencia orange genes. The pathogenicity of P. italicum may be due to the activation of effectors, including 51 small secreted cysteine-rich proteins, 110 carbohydrate-active enzymes, and 12 G protein-coupled receptors. Additionally, 211 metabolites related to the interactions between P. italicum and Valencia orange were identified by gas chromatography-time of flight mass spectrography, three of which were further confirmed by ultra-high performance liquid chromatography triple quadrupole mass spectrometry. A metabolomics analysis indicated that P. italicum pathogenicity is associated with the sphingolipid and salicylic acid signaling pathways. Moreover, a correlation analysis between the metabolite contents and gene expression levels suggested that P. italicum induces carbohydrate metabolism in Valencia orange fruits as part of its infection strategy. This study provides useful information regarding the genomic determinants that drive the evolution of host specificity in Penicillium species and clarifies the host-plant specificity during the infection of Valencia orange by P. italicum . IMPORTANCE P. italicum GL_Gan1, a local strain in Guangzhou, China, was sequenced. Comparison of the genome of P. italicum GL_Gan1 with other pathogenic Penicillium species, P. digitatum and P. expansum , revealed that the expansion of protein families, genome restructuring, HGT, and positive selection pressure were related to the host range expansion of the analyzed Penicillium species. Moreover, gene gains or losses might be associated with the speciation of these Penicillium species. In addition, the molecular basis of host-plant specificity during the infection of Valencia orange ( Citrus sinensis ) by ...

Identification of Pathogenicity-Related Effector Proteins and the Role of Piwsc1 in the Virulence of Penicillium italicum on Citrus Fruits

“…Of the screened 29 candidate effector proteins, 5 proteins were finally considered as core effectors that met 4 requirements of the criteria designed in the pipeline. We predicted that secreted proteins accounted for 3.8% of the total proteins in P. italicum , which was consistent with reported 3.0%, 4.1%, 4.7%, and 5.1% for P. infestans , Penicillium digitatum_ PHI26, P. italicum GL_Gan1, and S. sclerotiorum , respectively [ 17 , 46 , 56 ]. A large portion of secreted proteins in P. italicum are enzymes that function as glycosyl hydrolases, proteinases, peptidases, RNases, and pectin lyases (GH55, PL1, and PL3).…”

“…Samples collected at 0 hpi were used to calibrate expression levels. The β-actin gene of P. italicum was used as an internal reference [ 17 ]. A combination of three biological replicates with three technical replicates of each reaction were used.…”

“…For example, PeNLP1 and PeLysMs produced by Penicillium expansum are the virulence effectors for the decay of apple fruits [ 12 , 13 ]. The activation of effector proteins CAZymes (carbohydrate-active enzymes) and SSCPs (small secreted cysteine-rich proteins) was regarded as an important strategy for P. italicum colonization on Valencia oranges [ 17 ].…”

Wide transcriptional outlook to uncover Penicillium expansum genes underlying fungal incompatible infection

“…Host specificity is defined by the specific recognition of a given host and its colonization. Many plant pathogens show a varied host range, while others are limited to certain species or specific plant families [ 1 , 2 ]. Postharvest diseases in fruits, are mostly produced by Penicillium fungal species, including Penicillium italicum, Penicillium digitatum, and Penicillium expansum .…”

Characterization and Functional Analysis of a New Calcium/Calmodulin-Dependent Protein Kinase (CaMK1) in the Citrus Pathogenic Fungus Penicillium italicum

“…However, such regulation mechanisms are rarely elucidated in P. italicum species. The latest reports revealed some key factors to control P. italicum virulence [ 20 , 21 ]. Nevertheless, more studies are necessary to identify more effectors to regulate P. italicum infection.…”