EXAMINING INTERACTIONS AMONG FUNGAL INFECTION, SLEEP, AND HOST DEFENSE IN POPULATIONS OF WORLDWIDE, SLEEP INBRED PANEL, AND MUTANT DROSOPHILA MELANOGASTER

Abstract

Previous studies with mutant Drosophila melanogaster lines and the Drosophila Genetic Reference Panel (DGRP) reveal substantial variation in susceptibility to infection with Metarhizium anisopliae strain Ma549. These differences likely arise from variations in immunity, physiology, and behavior, yet the role of selection pressures in maintaining these disparities remains understudied. Using global Drosophila populations, the Sleep Inbred Panel (SIP), and sleep-deprived mutants, we investigated the interactions among fungal infection, sleep, and host defense. Testing 14,957 male and 15,287 female flies from 43 lines across 28 locations, we found that resistance to Ma549 correlates with latitudinal gradients in sleep duration, temperature, and humidity. Tropical populations may exhibit stronger defenses due to fungal diversity; however, the most disease-resistant males were also more susceptible to desiccation, indicating trade-offs between abiotic stress and disease resistance. Longer-sleeping males and virgin flies survived infections longer, and increased daytime sleep post-infection was particularly protective in resistant flies. These findings suggest that sleep and disease resistance are interrelated traits possibly shaped by clinal evolution. Using 10,917 males and 11,166 females selected for extreme long or short nighttime sleep duration, we found that short-sleepers, despite having fragmented sleep when healthy, outlived long-sleepers after Ma549 infection. Resistance differences were sex-specific: males were more resistant among short-sleepers, while females showed higher resistance among long-sleepers. Daytime sleep bout numbers correlated with dimorphic disease resistance. Additionally, Ma549 infection increased daytime sleep in both short- and long-sleepers, with short-sleeping males nearly matching long-sleepers in sleep duration post-infection. Virgins, regardless of sleep status, slept more and survived infection longer, indicating that sleep traits, sex, and mating status are closely linked to disease resistance. The study highlights that circadian rhythms influence sleep and immunity, with the sleep-deprived Shmns mutant failing to undergo sickness sleep and succumbing quickly to infection. Mutants with disrupted circadian rhythms (PER and CLK) also showed impaired sickness sleep; however, only the per gene offered protection against disease, while the Clk mutant had increased survival. Independent of mutant status, males slept more than females, and virgins slept more than mated flies, emphasizing the significance of circadian rhythms in sleep and disease resistance.