Multiple stressors produce differential transcriptomic patterns in a stream-dwelling salamander

Abstract

Background Global biodiversity is decreasing at an alarming rate and amphibians are at the forefront of this crisis. Understanding the factors that negatively impact amphibian populations and effectively monitoring their health are fundamental to addressing this epidemic. Plasma glucocorticoids are often used to assess stress in amphibians and other vertebrates, but these hormones can be extremely dynamic and impractical to quantify in small organisms. Transcriptomic responses to stress hormones in amphibians have been largely limited to laboratory models, and there have been few studies on vertebrates that have evaluated the impact of multiple stressors on patterns of gene expression. Here we examined the gene expression patterns in tail tissues of stream-dwelling salamanders ( Eurycea tynerensis ) chronically exposed to the stress hormone corticosterone under different temperature regimes. Results We found unique transcriptional signatures for chronic corticosterone exposure that were independent of temperature variation. Several of the corticosterone responsive genes are known to be involved in immune system response ( LY-6E ), oxidative stress ( GSTM2 and TRX ), and tissue repair ( A2M and FX ) . We also found many genes to be influenced by temperature ( CIRBP, HSC71, HSP40, HSP90, HSP70, ZNF593 ). Furthermore, the expression patterns of some genes ( GSTM2, LY-6E, UMOD, ZNF593, CIRBP, HSP90 ) show interactive effects of temperature and corticosterone exposure, compared to each treatment alone. Through a series of experiments we also showed that stressor induced patterns of expression were largely consistent across ages, life cycle modes, and tissue regeneration. Conclusions Outside of thermal stressors, the application of transcriptomes to monitor the health of non-human vertebrate systems has been vastly underinvestigated. Our study suggests that transcriptomic patterns harbor stressor specific signatures that can be highly informative for monitoring the diverse stressors of amphibian populations. Electronic supplementary material The online version of this article (10.1186/s12864-019-5814-y) contains supplementary material, which is available to authorized users.

Transcriptomic Changes in Hot Spring Frog Tadpoles (Buergeria otai) in Response to Heat Stress

“…Although the upregulation of HSP70 in those species is expected to function in the degradation of proteins misfolded due to the stress, it cannot explain the downregulation of HSP70 under the heat stress, which also leads to protein misfolding. The downregulation of HSP genes in response to heat stress (21 • C compared to 11 • C) was also observed in a salamander species (Clay et al, 2019). However, upregulation of the other HSP genes were simultaneously observed and the responses of these specific genes have not been discussed in the previous study.…”

Potential Effects of High Temperature and Heat Wave on Nanorana pleskei Based on Transcriptomic Analysis

“…These are unexpected results. HSP genes were likewise downregulated in E. tynerensis (Oklahoma salamander) [ 35 ] and B. otai tadpoles [ 23 ], but upregulated in Quasipaa spinosa [ 64 ] under heat stress. Heat shock proteins are induced by a variety of stressors, despite their name referring to their reaction to heat stress.…”

“…Heat shock protein ( HSP ) production is a typical event in prokaryotic and eukaryotic cells under stress conditions such as increased temperature and oxidative stress [ 34 ]. HSP genes were discovered to be downregulated in Oklahoma salamander Eurycea tynerensis [ 35 ] and Ota’s stream tree frog B. otai [ 23 ] under heat stress.…”

Exposure to glucocorticoids alters life history strategies in a facultatively paedomorphic salamander

“…Pools within each of the eight rows (row = block) of four mesocosms (8 × 4 = 32 mesocosms) were randomly assigned one of four treatments: Control (20 ml ethanol only), Low CORT (0.006 g CORT in 20 ml ethanol, for a 14.43 nM mesocosm water concentration), Medium CORT (0.03 g in 20 ml ethanol, for a 72.16 nM concentration) and High CORT (0.06 g in 20 ml ethanol, for a 144.31 nM concentration). CORT is readily absorbed via porous branchial and dermal tissue in amphibians (Clay et al, 2019; Glennemeier & Denver, 2002a; Krain & Denver, 2004; Middlemis Maher et al, 2013; Wack et al, 2010). A concentration of 125 nM has been shown to raise whole‐body CORT content of Rana pipiens tadpoles by approximately 35% (Glennemeier & Denver, 2002b), which corresponds to larval salamander CORT content that falls within the natural range of circulating CORT for Ambystoma (Cooperman et al, 2004; Homan et al, 2003a; 2003b; Houck et al, 1996).…”