Demethylation inhibitors (DMIs), including prochloraz, are popular fungicides to control citrus postharvest pathogens such as
Penicillium digitatum (green mold). However, many
P. digitatum strains have developed prochloraz resistance, which decreases drug efficacy. Specific major facilitator superfamily (MFS) transporter gene
mfs2, encoding drug-efflux
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Demethylation inhibitors (DMIs), including prochloraz, are popular fungicides to control citrus postharvest pathogens such as
Penicillium digitatum (green mold). However, many
P. digitatum strains have developed prochloraz resistance, which decreases drug efficacy. Specific major facilitator superfamily (MFS) transporter gene
mfs2, encoding drug-efflux pump protein MFS2, has been identified in
P. digitatum strain F6 (PdF6) to confer fungal strain prochloraz resistance. However, except for the drug-efflux pump function of MFS2, other mechanisms relating to the Pd
mfs2 are not fully clear. The present study reported a transcriptome investigation on the
mfs2-defective
P. digitatum strain. Comparing to the wild-type strain, the
mfs2-defective strain showed 717 differentially expressed genes (DEGs) without prochloraz induction, and 1221 DEGs with prochloraz induction. The obtained DEGs included multiple isoforms of MFS transporter-encoding genes, ATP-binding cassette (ABC) transporter-encoding genes, and multidrug and toxic compound extrusion (MATE) family protein-encoding genes. Many of these putative drug-efflux pump protein-encoding genes had significantly lower transcript abundances in the
mfs2-defective
P. digitatum strain at prochloraz induction, as compared to the wild-type strain, including twenty-two MFS transporter-encoding genes (
MFS1 to
MFS22), two ABC transporter-encoding genes (
ABC1 and
ABC2), and three MATE protein-encoding genes (
MATE1 to
MATE3). The prochloraz induction on special drug-efflux pump protein genes in the wild-type strain was not observed in the
mfs2-defective strain, including
MFS21,
MFS22,
ABC2,
MATE1,
MATE2, and
MATE3. On the other hand, the up-regulation of other drug-efflux pump protein genes in the
mfs2-defective strain cannot recover the fungal prochloraz resistance, including
MFS23,
MFS26,
MFS27,
MFS31,
MFS33, and
ABC3 to
ABC8. The functional enrichment of DEGs based on Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and euKaryotic Orthologous Groups (KOG) database resources suggested some essential contributors to the
mfs2-relating prochloraz resistance, including ribosome biosynthesis-related genes, oxidative phosphorylation genes, steroid biosynthesis-related genes, fatty acid and lipid metabolism-related genes, and carbon- and nitrogen-metabolism-related genes. The results indicated that the MFS2 transporter might be involved in the regulation of multiple drug-efflux pump protein gene expressions and multiple metabolism-related gene expressions, thus playing an important role in developing
P. digitatum prochloraz resistance.
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