Parental effects in a filamentous fungus : Phenotype, fitness and mechanism

Abstract

In nature, organisms have to cope with constantly changing environments. In certain conditions, it may be advantageous for the parents to pass on information about the environment, or resources to their offspring. Such transfers are known as parental effects, and they are well documented in plants and animals, but not in other eukaryotes, such as fungi. Many fungi disperse through spores, and fungal spores can potentially carry information or resources to the next generation. Understanding parental effects and their evolutionary consequences in fungi is of vital importance as they perform crucial ecosystem functions. In this study, we investigated whether parental effects are present in the filamentous fungus Neurospora crassa, how long do they last, whether the effects are adaptive, and what is their mechanism. We performed a fully factorial match/mismatch experiment for a good and a poor quality environment, in which we measured the initial growth of strains that experienced either a matched or mismatched environment in their previous generation. We found a strong silver-spoon effect in initial mycelium growth, which lasted for one generation, and increased fitness during competition experiments. By using deletion mutants that lacked key genes in epigenetic processes, we show that epigenetic mechanisms are not involved in this effect. Instead, we show that spore glycogen content, glucose availability and a radical transcription shift in spores are the main mechanisms behind this parental effect.