Diversity of Polyketide Synthases in Fusarium
Daren W. Brown and Robert H. Proctor
from: Fusarium: Genomics, Molecular and Cellular Biology (Edited by: Daren W. Brown and Robert H. Proctor). Caister Academic Press, U.K. (2013)
Fusarium can produce a structurally diverse array of secondary metabolites (SMs) with a range of biological activities, including pigmentation, plant growth regulation, and toxicity to humans and other animals. Contamination of grain-based food and feed with toxic SMs produced by Fusarium is associated with a variety of diseases in plants and animals and results in loss of millions of dollars in grain commodities each year. Many SMs are formed via the activities of a family of large enzymes called polyketide synthases (PKSs) that consist of between five and eight functional domains. This Chapter reviews the structures and functions of Fusarium PKSs present in four species, Fusarium verticillioides, Fusarium graminearum, Fusarium solani and Fusarium oxysporum. Each genome has between 11 and 16 PKS genes. Re-examination of inferred phylogenetic relationships of deduced amino acid sequences provides insight into how this gene family evolved. The geneaologies suggest that collectively the Fusarium PKSs represent 36 distinct sets of PKS homologs, where each set catalyzes synthesis of a structurally distinct polyketide. Variation in Fusarium PKS genes is due to both ancient and recent gene duplications, gene loss events, gain-of-function due to the acquisition of new domains, and of loss-of-function due to nucleotide mutations. The significant number and variety of evolutionary changes reflects a vast biosynthetic potential this gene family provides fungi and that may help them adapt to changing environmental conditions. Understanding how fungal polyketides are synthesized should lead to better methods to control their production and thereby reduce their negative impact on human endevors read more ...