A polyketide synthase gene cluster associated with the sexual reproductive cycle of the banana pathogen, Pseudocercospora fijiensis

Abstract

Disease spread of Pseudocercospora fijiensis , causal agent of the black Sigatoka disease of banana, depends on ascospores produced through the sexual reproductive cycle. We used phylogenetic analysis to identify P . fijiensis homologs (PKS8-4 and Hybrid8-3) to the PKS4 polyketide synthases (PKS) from Neurospora crassa and Sordaria macrospora involved in sexual reproduction. These sequences also formed a clade with lovastatin, compactin, and betaenone-producing PKS sequences. Transcriptome analysis showed that both the P . fijiensis Hybrid8-3 and PKS8-4 genes have higher expression in infected leaf tissue compared to in culture. Domain analysis showed that PKS8-4 is more similar than Hybrid8-3 to PKS4. pPKS8-4:GFP transcriptional fusion transformants showed expression of GFP in flask-shaped structures in mycelial cultures as well as in crosses between compatible and incompatible mating types. Confocal microscopy confirmed expression in spermagonia in leaf substomatal cavities, consistent with a role in sexual reproduction. A disruption mutant of pks8-4 retained normal pathogenicity on banana, and no differences were observed in growth, conidial production, and spermagonia production. GC-MS profiling of the mutant and wild type did not identify differences in polyketide metabolites, but did identify changes in saturated fatty acid methyl esters and alkene and alkane derivatives. To our knowledge, this is the first report of a polyketide synthase pathway associated with spermagonia.

Size‐exclusion chromatography allows the isolation of EVs from the filamentous fungal plant pathogen Fusarium oxysporum f. sp. vasinfectum (Fov)

“…Both types of EVs were enriched with a polyketide synthase (X0LBU9) and a fusarubin cluster-esterase (X0KPE5), which may be involved in the production of pigments [45]. Polyketide synthases have been recognized as important machinery in the production of toxins from fungal pathogens of maize [46], banana [47], tobacco [48] and wheat [49], while the fusarubin cluster-esterase contributes to the production of the toxic pigment fusarubin, and has been detected in other pathogenic Fusarium species [50]. One enniatin synthase (X0KNM9) detected only in SDB EVs is involved in the production of enniatins and beauvericin, which are cyclic mycotoxins.…”

Deletion of a Rare Fungal PKS CgPKS11 Promotes Chaetoglobosin A Biosynthesis, Yet Defers the Growth and Development of Chaetomium globosum

“…Substantial data demonstrated that PKS-derived melanin is required for the development of asexual and sexual structures of fungi that might function as protectants against harmful environmental conditions. Deficiency of PKSs responsible for pigment biosynthesis usually had a negative effect on sexual development [19,[33][34][35]. Indeed, we previously demonstrated that downregulation of PKS-1/Alb1, a key enzyme responsible for pigment biosynthesis displayed a pigmentdeficient phenotype and lost the ability to produce ascospores in C. globosum [19].…”

A polyketide synthase gene cluster required for pathogenicity of Pseudocercospora fijiensis on banana

“…fijiensis , given our interest in the polyketide toxin cercosporin in the related Cercospora species, as well as the importance of polyketides in pathogenicity by diverse fungi. In past work we identified one gene cluster ( PKS8-4 ) as being involved in spermagonia production during the sexual reproductive cycle [ 36 ]. Another PKS gene cluster ( PKS8-1 ) was shown to be conserved across three other Pseudocercospora species ( P .…”

“…Cercosporin is a perylenequinone produced through a polyketide synthase (PKS) pathway, thus previous work in the laboratory has focused on polyketide synthase gene clusters in P . fijiensis [ 34 – 36 ]. We conducted bioinformatics analyses that identified seven PKS genes ( PKS2-1 , PKS7-1 , PKS8-1 , PKS8-2 , PKS8-4 , PKS10-1 , and PKS10-2 ) and one hybrid PKS-nonribosomal peptide synthetase (NRPS) gene ( Hybrid8-3 ) in the P .…”

“…Characterization of the PKS8-4 and Hybrid8-3 clusters identified them as playing a role in the sexual reproductive cycle of P . fijiensis , an important discovery as the plant-to-plant spread of the fungus is primarily through ascospores [ 36 ]. Phylogenetic analysis identified similarities to polyketide synthases involved in sexual reproduction in Neurospora crassa and Sordaria macrospora [ 40 ].…”