Lipoxygenase Activity Accelerates Programmed Spore Germination in Aspergillus fumigatus

Abstract

The opportunistic human pathogen <i>Aspergillus fumigatus</i> initiates invasive growth through a programmed germination process that progresses from dormant spore to swollen spore (SS) to germling (GL) and ultimately invasive hyphal growth. We find a lipoxygenase with considerable homology to human Alox5 and Alox15, LoxB, that impacts the transitions of programmed spore germination. Overexpression of <i>loxB</i> (<i>OE::loxB</i>) increases germination with rapid advance to the GL stage. However, deletion of <i>loxB</i> (<i>ΔloxB</i>) or its signal peptide only delays progression to the SS stage in the presence of arachidonic acid (AA); no delay is observed in minimal media. This delay is remediated by the addition of the oxygenated AA oxylipin 5-hydroxyeicosatetraenoic acid (5-HETE) that is a product of human Alox5. We propose that <i>A. fumigatus</i> acquisition of LoxB (found in few fungi) enhances germination rates in polyunsaturated fatty acid-rich environments.