Biosynthesis of Annullatin D in Penicillium roqueforti Implies Oxidative Lactonization between Two Hydroxyl Groups Catalyzed by a BBE-like Enzyme.

Annullatins from Cordyceps annullata are alkylated aromatic polyketides including annullatin D with a fused dihydrobenzofuran lactone ring system. Here, we report the identification of a silent biosynthetic gene cluster for annullatins from Penicillium roqueforti by heterologous expression in Aspergillus nidulans, gene deletion, and feeding experiments as well as by biochemical characterization. The polyketide core structure is consecutively modified by hydroxylation and prenylation. A berberine bridge enzyme-like protein catalyzes the final step, an oxidative lactonization between two hydroxyl groups, to form (2S, 9S)-annullatin D.

Dual function of a secreted fungalysin metalloprotease in Ustilago maydis.

Fungalysins from several phytopathogenic fungi have been shown to be involved in cleavage of plant chitinases. While fungal chitinases are responsible for cell wall remodeling during growth and morphogenesis, plant chitinases are important components of immunity. This study describes a dual function of the Ustilago maydis fungalysin UmFly1 in modulation of both plant and fungal chitinases. Genetic, biochemical and microscopic experiments were performed to elucidate the in vitro and in planta functions of U. maydis UmFly1. U. maydis ∆umfly1 mutants show significantly reduced virulence, which coincides with reduced cleavage of the maize chitinase ZmChiA within its chitin-binding domain. Moreover, deletion of umfly1 affected the cell separation of haploid U. maydis sporidia. This phenotype is associated with posttranslational activation of the endogenous chitinase UmCts1. Genetic complementation of the ∆umfly1 mutant with a homologous gene from closely related, but nonpathogenic, yeast fully rescued the cell separation defect in vitro, but it could not recover the ∆umfly1 defect in virulence and cleavage of the maize chitinase. We report on the dual function of the secreted fungalysin UmFly1. We hypothesize that co-evolution of U. maydis with its host plant extended the endogenous function of UmFly1 towards the modulation of plant chitinase activity to promote infection.