Expression Pattern of Entire Cytochrome P450 Genes and Response of Defensomes in the Benzo[a]pyrene-Exposed Monogonont Rotifer Brachionus koreanus

Abstract

Cytochrome P450 (CYP) proteins are involved in the first line of detoxification mechanism against diverse polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P). In aquatic invertebrates, there is still a lack of knowledge on the CYP genes involved in the molecular response to B[a]P exposure due to limited gene information. In this study, we cloned the entire 25 CYP genes in the monogonont rotifer Brachionus koreanus with the aid of next generation sequencing (NGS) technologies and analyzed their transcript profiles with a real-time RT-PCR array to better understand B[a]P-triggered molecular response over different time courses. As a result, B[a]P exposure induced CYP2/3-involved detoxification mechanisms and defensome, including phase II detoxification and antioxidant systems with a modulation of the chaperone heat shock protein (hsp) expression but did not change expression of other CYP clans in B. koreanus . Therefore, we found that B[a]P induced a strong detoxification mechanism to overcome detrimental effects of B[a]P associated with B[a]P-induced growth retardation as a trade-off in fitness costs. Also, this approach revealed that the entire CYP profiling can be a way of providing a better understanding on the mode of action of B[a]P in B. koreanus with respect to molecular defense metabolism.

Significance of adverse outcome pathways in biomarker-based environmental risk assessment in aquatic organisms

“…Moreover, the complete CYP gene sequences are known for rotifers. Thus, this information could be applied to metabolomics-based studies of risk assessment for waterborne xenobiotics, such as BαP and other hazardous and persistent aquatic pollutants (Kim et al, 2013). Cumulatively, these data indicate that rotifers have great potential as bioindicator species to study xenobiotic metabolism and the effects of xenobiotics on detoxification and oxidative stress Yang et al, 2013aYang et al, , 2013bYang et al, , 2013c in AOP development.…”

“…Furthermore, extensive genomic DNA and RNA-seq databases give these species an advantage over other aquatic invertebrate species with less complete genomics databases (Raisuddin et al, 2007;Lee et al, 2010;Colbourne et al, 2011;Dahms et al, 2011;Lee et al, 2011;Hwang et al, 2013a,b;De Coninck et al, 2014 the rotifer B. koreanus is an ideal species for the development of an AOP, since these organisms are widely distributed along marine and estuarine coastal lines. These rotifers also possess other desirable characteristics such as an abundant population, ease of cultivation, small size, and short generation cycle (Yoshinaga et al, 2003;Dahms et al, 2011;Kim et al, 2013) (Fig. 3).…”

“…Rotifers play a critical role in the aquatic food web; thus, risk assessment using an AOP framework can be used to systematically interpret community-wide effects in response to chemical exposure. Genomic DNA and RNA-seq databases of rotifers provide a wealth of information from which diverse MIEs in response to environmental pollutant exposure can be obtained Kim et al, 2013;Rhee et al, 2013b). Moreover, the complete CYP gene sequences are known for rotifers.…”

“…Although weak EROD activity and CYP1A-immunoreactivity have been observed in invertebrates (Livingstone, 1998;Peters et al, 1998;Chaty et al, 2004;Rewitz et al, 2006;David et al, 2012), the AhR ligand is unable to signal via TCDD or βNF in a number of aquatic invertebrates (e.g., molluscs and Caenorhabditis elegans) (Hahn, 2002). The different profiles of EROD activity imply that the presence of different CYP isoforms generates diverse PAH metabolic processes in rotifers, copepods, fish, and the crustacean Aristeus antennatus (Koenig et al, 2012;Kim et al, 2013;Rhee et al, 2013a;Han et al, 2014). Another relevant issue is interspecific differences of nuclear receptors.…”

Dose- and time-dependent expression of aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (ARNT) in PCB-, B[a]P-, and TBT-exposed intertidal copepod Tigriopus japonicus

“…In invertebrates, the expression patterns of 25 CYP genes were measured in the rotifer Brachionus koreanus in response to benzo[a]pyrene (B[a]P) (Kim et al, 2013). Several key CYP genes involved in the detoxification mechanism are susceptible to B[a]P exposure in B. koreanus.…”