Live cell imaging of lipid droplet distribution and motility in the filamentous fungus Ustilago maydis

Abstract

Lipid droplets (LDs) are organelles specialised for lipid metabolism and storage, found across the domains of life. They are dynamic in number and size, actively transported, and have diverse functions, many of which have only recently been identified. Despite this, they remain less well-characterised than many other organelles. While the motility of LDs has been noted in filamentous fungi, no study has yet investigated its mechanism. In this study, several techniques were established for visualisation of LDs in live cells of the dimorphic fungus Ustilago maydis. This species is a prominent pathogen of maize (Zea mays) and an established model organism for intracellular trafficking. Distribution and motility patterns of LDs were investigated quantitatively in U. maydis cells under varying growth conditions, including during plant infection. Active transport of LDs was found to be microtubule-dependent, and dependent on specific motor proteins and organelle interactions.