A microsporidia possesses robust transcriptional response to heat shock impacting diverse cellular processes despite lack of HSF. A microsporidia possesses robust transcriptional response to heat shock impacting diverse cellular processes despite lack of HSF

The majority of fungal species prefer the 12°–30° C range and relatively few species tolerate temperatures higher than 35° C . Our understanding of the mechanisms underpinning the ability of some species to grow at higher temperatures is incomplete. Nosema ceranae is an obligate intracellular fungal parasite that infects honey bees and can cause individual mortality and contribute to colony collapse. Despite a reduced genome, this species is strikingly thermotolerant, growing optimally at the colony temperature of 35° C. In characterizing the HSR in N. ceranae, we found that this and other microsporidian species have lost the transcriptional regulator HSF and possess a reduced set of putative core HSF1-dependent HSR target genes. Despite these losses, N. ceranae demonstrates robust upregulation of the remaining HSR target genes after heat shock. In addition, thermal stress leads to alterations in genes involved in various metabolic pathways, ribosome biogenesis and translation, and DNA repair. These results provide important insight into the stress responses of microsporidia. Such new understanding will allow new comparisons with other pathogenic fungi and potentially enable discovery of novel treatment strategies for microsporidia infections affecting food production and human health. Overall design: Six samples at 2 temperatures

绝大多数真菌物种偏好12℃~30℃的温度区间，仅有相对较少的物种能够耐受35℃以上的高温。目前学界对部分真菌物种在高温环境下生长的分子机制仍缺乏完整认知。东方蜜蜂微孢子虫（Nosema ceranae）是一种专性胞内真菌寄生虫，可感染蜜蜂并引发蜜蜂个体死亡，还会加剧蜂群崩坏现象。尽管该物种的基因组发生了缩减，但其耐热能力却极为突出，最适生长温度恰好为蜂群内部的35℃。在表征东方蜜蜂微孢子虫的热休克反应（Heat Shock Response, HSR）过程中，我们发现该物种与其他微孢子虫（Microsporidia）均已丢失转录调节因子HSF（热休克因子，Heat Shock Factor），且仅拥有一套规模缩减的、推测为HSF1依赖型的热休克反应靶基因核心集合。尽管存在上述基因丢失事件，东方蜜蜂微孢子虫在热激处理后仍可对剩余的热休克反应靶基因实现显著上调表达。此外，热应激还会引发参与多种代谢通路、核糖体生物发生、翻译过程以及DNA修复的基因表达发生改变。本研究结果为深入理解微孢子虫的应激反应提供了重要见解。这一新的认知将为与其他致病真菌的对比研究提供新的视角，还有望为开发针对影响粮食生产与人类健康的微孢子虫感染的新型治疗策略提供思路。实验整体设计：设置2个温度梯度，共6个样本。