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

## TL;DR

This study shows that the fungi Aspergillus nidulans uses HSP104 and HSP20-L to respond to attacks by the fungivorous springtail Sinella curviseta, helping maintain cellular balance.

## Contribution

The study reveals the specific roles of HSP104 and HSP20-L in fungal defense against biotic stress from a springtail.

## Key findings

- HSP104 and HSP20-L are upregulated in response to Sinella curviseta stress in Aspergillus nidulans.
- HSP104 and HSP20-L have opposing roles in conidia and ascospore formation under stress.
- Both proteins help reduce cellular damage and support chitin synthesis and antioxidant activity during development.

## Abstract

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.

The heat shock proteins HSP104 and HSP20‐L of
A. nidulans
exhibit a reciprocal regulatory relationship to maintain physiological homeostasis in response to
S. curviseta
‐induced stress.