HSP104 and HSP20-L Are Required by Aspergillus nidulans in Response to Attack by Fungivorous Springtail Sinella curviseta.

Heat shock proteins (HSPs) are conserved biomolecules that are consistently expressed and upregulated in response to stress. However, whether fungi activate HSPs in response to fungivorous arthropods' attack remains unclear. In this study, we investigated the function of HSP104 and HSP20-L in Aspergillus nidulans upon Sinella curviseta stress. The results revealed that hsp104 and hsp20-L were upregulated upon the stress. Knockout of hsp104 and/or hsp20-L inhibited conidia and cleistothecia formation. Additionally, S. curviseta stress inhibited conidia and cleistothecia formation in the wild-type strain. hsp104 positively regulated conidia formation in response to stress, while hsp20-L negatively regulated it. Notably, hsp104 and hsp20-L exhibited opposing functions on ascospore formation upon biotic stress. The absence of hsp104 and/or hsp20-L and S. curviseta stress resulted in increased cellular damage. During asexual development, both hsp104 and hsp20-L promoted chitin and β-glucan synthesis and catalase activity. During sexual development, only chitin synthesis was enhanced in Δhsp104 and Δhsp20-L. Under S. curviseta stress, HSP104 promoted chitin synthesis and catalase activity during asexual development, whereas HSP20-L promoted chitin and trehalose synthesis and superoxide dismutase activity during sexual development. Collectively, our results suggest that hsp104 and hsp20-L play a role in response to S. curviseta stress to maintain homeostasis.