Slight cooling during growth induced changes in filamentous fungi hypha mitochondrial morphology

Abstract

Adaptive changes in mitochondrial morphology are associated with changes in the mitochondrial function and metabolic fitness of eukaryotic cells. We previously described in young hyphae of the filamentous fungus Phycomyces blakesleeanus a dramatic effect of an increase in ambient temperature during growth: a 3°C warmer environment compared with a control temperature of 22°C resulted in the appearance of long elongated (“tubular”) mitochondria accompanied by an increase in lipid droplet density. Here, we examined how cooler ambient temperature (18°C) during growth affects mitochondrial morphology in P. blakesleeanus compared with the control grown at 22°C. We used two-photon fluorescence imaging (TPEF) of live hyphae stained with the vital mitochondrial dye rhodamine 123. Extraction of relevant parameters (number, size, and shape of mitochondria) from TPEF images was performed using the Ilastik machine learning-based software. The suitability of the Ilastik analysis was compared with the Particle Analysis (ImageJ). Cold treatment resulted in the appearance of tubular mitochondrial morphology that was absent in the control group. Tubular mitochondrial morphology appears to be an adaptive feature that occurs in both warmer and colder conditions and is likely part of the stress response.