Digital gene expression analysis in the gills of Ruditapes philippinarum exposed to short- and long-term exposures of ammonia nitrogen

Abstract

Previous study revealed severe toxic effects of ammonia nitrogen on Ruditapes philippinarum including lysosomal instability, disturbed metabolic profiles, gill tissues with damaged structure, and variation of neurotransmitter concentrations. However, the underlying molecular mechanism was not fully understood yet. In the present study, digital gene expression technology (DGE) was applied to globally screen the key genes and pathways involved in the responses to short- and long-term exposures of ammonia nitrogen. Results of DGE analysis indicated that short-term duration of ammonia exposure affected pathways in Dorso-ventral axis formation, Notch signaling, thyroid hormone signaling and protein processing in endoplasmic reticulum. The long-term exposure led to DEGs significantly enriched in gap junction, immunity, signal and hormone transduction, as well as key substance metabolism pathways. Functional research of significantly changed DEGs suggested that the immunity of R. philippinarum was weakened heavily by toxic effects of ammonia nitrogen, as well as neuro-transduction and metabolism of important substances. Taken together, the present study provides a molecular support for the previous results of the detrimental toxicity of ammonia exposure in R. philippinarum, further work will be performed to investigate the specific genes and their certain functions involved in ammonia toxicity to molluscs.

Effects of ammonia nitrogen on gill mitochondria in clam Ruditapes philippinarum

“…Ca 2+ -ATPase activities were found to be significantly inhibited, especially in the high ammonia exposed-group, which suggested that calcium metabolism was disturbed by ammonia exposure. In our previous study, calcium metabolism-related genes were found to be significantly altered during a 30-day exposure to ammonia characterized by a transcriptomic analysis (Cong et al, 2018), which is consistent with the present result. Since the calcium ion is a critical factor for the initiation and effectuation of cell death controlled by the mitochondria (Orrenius et al, 2015), the significant variation of Ca 2+ -ATPase might represent the disturbance in calcium regulation of gill mitochondria after ammonia exposure.…”

“…Compared with NH 4 + , NH 3 (ammonia nitrogen) can easily diffuse cross the cell membrane, and induce detrimental effects. It can seriously cause attenuated immune reactions, disturbed energy allocation, significant variations in important substance metabolism and gene expressions, and even decreased survival rates to the aquatic animals https://doi.org/10.1016/j.etap.2018.12.003 Received 27 September 2018; Received in revised form 7 November 2018; Accepted 2 December 2018 T (Keppler, 2007;Widman et al, 2008;Maas et al, 2012;Wang et al, 2012;Cong et al, 2017Cong et al, , 2018. In vertebrates, ammonia nitrogen was found to mainly induce mitochondrial permeability transition and neurotoxicity by activation of NMDA receptor-NO-cGMP pathway (Oja et al, 2017;Kosenko et al, 1994;Bai et al, 2001).…”

Transcriptomic Analysis of Gill and Hepatopancreas in Razor Clam (Sinonovacula constricta) Exposed to Acute Ammonia

“…Generally, there are mainly two chemical forms of ammonia in water, namely, ionized (NH 4 + ) and unionized (NH 3 ) form. The latter is more toxic as the NH 3 diffuse more easily across the cell membrane for its lipid solubility and non-polarity (Cong et al, 2018). Meantime, other environmental factors also affect the ratio of two forms of ammonia.…”

“…In Manila clam Ruditapes philippinarum, short-and longtern exposure to ammonia displayed the different responding patterns in the gill via digital gene expression analysis. It induced pathways of notch signaling and protein processing in endoplasmic reticulum in short-term exposure and pathways of gap junction, immunity, and key substance metabolism in longterm exposure (Cong et al, 2018). Digestive gland transcriptome analysis of response mechanism to ammonia in Asian clam Corbicula fluminea revealed that the immunity and apoptotic signaling pathways play important roles during stress (Zhang et al, 2019).…”

Genome-Wide Characterization of Alternative Splicing Events and Their Responses to Cold Stress in Tilapia

“…AS participates in organogenesis (Anand et al, 2008), development (Yamaguchi and Iwasa, 2018), tissue identity (Baralle and Giudice, 2017;Cong et al, 2018), disease occurrence (Scotti and Swanson, 2016;Martinez-Montiel et al, 2018) and heavy metals, cold and heat, pathogen attacks (Christensen et al, 1992;Hopf et al, 1992;Ali and Reddy, 2008;Mazzucotelli et al, 2008) in eukaryotes.…”