Molecular cloning and expression profile of snow trout GPDH gene in response to abiotic stress

PPAR Signaling Maintains Metabolic Homeostasis under Hypothermia in Freshwater Drum (Aplodinotus grunniens)

Aplodinotus grunniens, known as freshwater drum, is a kind of eurythermal freshwater fish that is widely distributed in North America. In 2019, our research group reached a milestone on its artificial breeding and cultivation and have investigated its physiological adaption to the environment, providing a breakthrough and prospects for aquaculture. However, its adaptability and metabolic homeostasis to hypothermia is not fully understood. In this experiment, cold stress was conducted at 18 °C (LT18) and 10 °C (LT10) with 25 °C as control (Con) for 8 days to explore the effects of short-term hypothermia on the physiology and metabolism of freshwater drum. From the results, the level of free essential amino acids in LT18 and LT10 decreased significantly after 2 days cold stress compared with Con. Furthermore, plasma total triglyceride (TG) content and lipase (LPS) activity were decreased at LT10 for 2d. With RNA-seq in the liver, metabolic-related signaling, especially amino acid synthesis and lipid metabolism, was inhibited by hypothermia. Specifically, the PPAR signaling pathway is correlated with the inhibition of lipid and amino acid metabolism induced by hypothermia. These data confirmed that PPAR signaling maintains lipid and amino acid metabolic homeostasis during cold stress. These results give a theoretical foundation for hypothermia resistance in the area of metabolic homeostasis for freshwater drum.

An updated review of cold shock and cold stress in fish

Temperature is critical in regulating virtually all biological functions in fish. Low temperature stress (cold shock/stress) is an often-overlooked challenge that many fish face as a result of both natural events and anthropogenic activities. In this study, we present an updated review of the cold shock literature based on a comprehensive literature search, following an initial review on the subject by M.R. Donaldson and colleagues, published in a 2008 volume of this journal. We focus on how knowledge on cold shock and fish has evolved over the past decade, describing advances in the understanding of the generalized stress response in fish under cold stress, what metrics may be used to quantify cold stress and what knowledge gaps remain to be addressed in future research. We also describe the relevance of cold shock as it pertains to environmental managers, policymakers and industry professionals, including practical applications of cold shock. Although substantial progress has been made in addressing some of the knowledge gaps identified a decade ago, other topics (e.g., population-level effects and interactions between primary, secondary and tertiary stress responses) have received little or no attention despite their significance to fish biology and thermal stress. Approaches using combinations of primary, secondary and tertiary stress responses are crucial as a research priority to better understand the mechanisms underlying cold shock responses, from short-term physiological changes to individual- and population-level effects, thereby providing researchers with better means of quantifying cold shock in laboratory and field settings.

Transcriptional response to heat shock in liver of snow trout (Schizothorax richardsonii)--a vulnerable Himalayan Cyprinid fish

The snow trout (Schizothorax richardsonii) belonging to family Cyprinidae, is an endemic fish of the Himalayan region. The species is tagged as vulnerable species in the IUCN red list of threatened species. The fish thrives well in snowmelt water of several streams and rivers in the region but are occasionally exposed to more than 20 °C during the summer season. Therefore, we have used deep RNA sequencing to decipher the transcriptome of snow trout and characterize the genes and molecular pathways involved in heat shock response. In this study 72,601,298 and 65,428,283 raw reads for heat-shocked and control, respectively, were obtained by Illumina paired-end sequencing technology. The de novo assembled transcriptome was tested for differential gene expression across the treatment groups. The quality of assembly was high with N75 and N50 lengths of 461 and 1274 bases, respectively. A total of 65 unique transcripts were differentially expressed in liver under heat shock and control. Annotated blast matches reveal that differentially expressed transcripts correspond to critical chaperones and molecular pathways, previously shown to be important for thermal stress in other fish species. Eight randomly selected heat-stressed responsive transcripts were also observed to be upregulated during qRT-PCR analysis. This study is the preliminary step to understanding the responses during sudden environmental changes like heat shock. The reference transcriptome database would also aid further studies on biological and physiological aspects of the snow trout under abiotic stresses.