Small heat shock proteins, phylogeny in filamentous fungi and expression analyses in Aspergillus nidulans

• Small heat shock proteins were highly diverged in filamentous fungi.
• Recent gene duplication played a crucial role in sSHP evolution.
• sSHPs in A. nidulans were involved in response to various stresses.

Small heat shock proteins (sHSPs) have been characterized in organisms from all three domains of life and viruses and are involved in a wide range of biological functions. However, the evolution and function of sHSP in Aspergillus species are largely unknown. In the present work, sHSPs were identified in 31 filamentous fungi, including species from Aspergillus, Penicillium, Fusarium and Magnaporthe, as well as Botrytis cinerea and Neurospora crassa. Phylogenetic analysis revealed high level of divergence of sHSPs among filamentous fungi that orthologs could be only found between very closely related species. Strikingly, duplication of shsp genes occurred in genera Penicillium and also Aspergillus nidulans was observed, which might be an important pathway of sHSPs evolution. Expression analysis of shsp genes revealed that sHSPs were involved in response of A. nidulans to various conditions, including cold/heat as well as oxidative and osmotic stresses, and that the recent duplicated sHSPs in A. nidulans had highly similar function.