Table_1_Gill Transcriptomic Responses to Toxin-producing Alga Prymnesium parvum in Rainbow Trout.xlsx

The gill of teleost fish is a multifunctional organ involved in many physiological processes, including protection of the mucosal gill surface against pathogens and other environmental antigens by the gill-associated lymphoid tissue (GIALT). Climate change associated phenomena, such as increasing frequency and magnitude of harmful algal blooms (HABs) put extra strain on gill function, contributing to enhanced fish mortality and fish kills. However, the molecular basis of the HAB-induced gill injury remains largely unknown due to the lack of high-throughput transcriptomic studies performed on teleost fish in laboratory conditions. We used juvenile rainbow trout (Oncorhynchus mykiss) to investigate the transcriptomic responses of the gill tissue to two (high and low) sublethal densities of the toxin-producing alga Prymnesium parvum, in relation to non-exposed control fish. The exposure time to P. parvum (4–5 h) was sufficient to identify three different phenotypic responses among the exposed fish, enabling us to focus on the common gill transcriptomic responses to P. parvum that were independent of dose and phenotype. The inspection of common differentially expressed genes (DEGs), canonical pathways, upstream regulators and downstream effects pointed towards P. parvum-induced inflammatory response and gill inflammation driven by alterations of Acute Phase Response Signalling, IL-6 Signalling, IL-10 Signalling, Role of PKR in Interferon Induction and Antiviral Response, IL-8 Signalling and IL-17 Signalling pathways. While we could not determine if the inferred gill inflammation was progressing or resolving, our study clearly suggests that P. parvum blooms may contribute to the serious gill disorders in fish. By providing insights into the gill transcriptomic responses to toxin-producing P. parvum in teleost fish, our research opens new avenues for investigating how to monitor and mitigate toxicity of HABs before they become lethal.

鲈形鱼类的鳃为一种多功能的器官，参与多种生理过程，包括通过鳃相关淋巴组织（GIALT）保护黏膜鳃表面免受病原体及其他环境抗原的侵害。气候变化相关的现象，如有害藻华（HABs）频率和强度的增加，对鳃功能施加额外压力，导致鱼类死亡率上升和鱼类死亡事件。然而，由于缺乏在实验室条件下对鲈形鱼类进行的高通量转录组学研究，HAB诱导的鳃损伤的分子基础尚不明确。本研究以幼年彩虹鳟（Oncorhynchus mykiss）为研究对象，探讨了鳃组织对产毒藻Prymnesium parvum产生的两种（高、低）亚致死密度毒素的转录组反应，并与之暴露于无暴露对照鱼类进行对比。P. parvum暴露时间（4-5小时）足以在受暴露鱼类中识别出三种不同的表型反应，从而使我方能聚焦于P. parvum引起的，独立于剂量和表型的共同鳃转录组反应。对共同差异表达基因（DEGs）、经典通路、上游调节因子及下游效应的检查指向了P. parvum诱导的炎症反应和由急性期反应信号、IL-6信号、IL-10信号、PKR在干扰素诱导和抗病毒反应中的作用、IL-8信号和IL-17信号通路驱动的鳃炎症。尽管我们无法确定推测的鳃炎症是进展还是缓解，但本研究明确表明，P. parvum的爆发可能对鱼类严重的鳃病变作出贡献。本研究通过揭示鲈形鱼类对产毒P. parvum的鳃转录组反应，为调查如何在HABs成为致命之前监测和减轻其毒性开辟了新的研究途径。