Differentiation and hydrogen peroxide production in Sclerotium rolfsii are induced by the oxidizing growth factors, light and iron

Abstract

Hydrogen peroxide is produced by Sclerotium rolfsii during sclerotial differentiation, in response to oxidative growth conditions of light and Fe. An additive effect of (± light ± Fe)-induced oxidative stress is observed on H₂O₂ production levels and on sclerotia numbers during fungal development. High H₂O₂ production rates are correlated with high oxidative stress and are observed in less lipid-peroxidized young mycelia and sclerotia (sclerotia initials and early developing sclerotia) and not in differentiated, highly lipid-peroxidized older mycelia and sclerotia (developed and mature sclerotia). H₂O₂ production by undifferentiated mycelia and their exposure to exogenous H₂O₂ show a rate/dose-dependent correlation with degree of sclerotial differentiation (sclerotia numbers). Hydrogen peroxide and lipid peroxide concentration gradients are observed in fungal colonies during their transition from undifferentiated (mycelial) to differentiated (sclerotial) stage. Growth-stage-dependent changes in H₂O₂ production rates during development are not due to changes in glucose concentration and pH of the growth medium. Light/Fe-induced H₂O₂ production and its effect on S. rolfsii differentiation, are discussed in the context of our hypothesis of oxidative stress-induced sclerotial differentiation.

Key Words:

• fungi
• lipid peroxidation
• oxidative stress
• sclerotial differentiation