Opening Address

Atsushi HAGIWARA 한국수산과학회 양식분과 2014 한국수산과학회 양식분과 학술대회 Vol.2014 No.10

Phototactic behavior of live food rotifer <i>Brachionus plicatilis</i> species complex and its significance in larviculture: A review

Kim, Hee-Jin,Lee, Jae-Seong,Hagiwara, Atsushi Elsevier 2018 Aquaculture Vol.497 No.-

<P><B>Abstract</B></P> <P>We review a recent progress of photophysiological studies in the rotifer <I>Brachionus plicatilis</I> species complex. The rotifers have a light sensor i.e., eyespot inducing phototactic behavior. For the rotifer <I>B. plicatilis</I> sp. complex, the eyespot efficiently absorbs the light wavelength ranging from 450 to 550 nm. The function of eyespot is affected by diet species from 30-day batch cultures fed by either microalgae <I>Nannochloropsis oculata</I> or baker's yeast <I>Saccharomyces cerevisiae</I>. By feeding baker's yeast, rotifer eyespot gradually lost its function: area (5.5 times) and absorbance (2.2 times) decrease compared to those fed by <I>N. oculata</I>. Phototactic behavior and reproductive characteristics of the rotifer <I>B. plicatilis</I> sp. complex varied with different light wavelengths and intensities. The rotifers show light wavelength dependent phototaxis associated with the reception of an eyespot. For the phototactic behavior in horizontal level, light intensity is also a significant factor to regulate phototaxis. The rotifers show strong positive phototaxis under blue (peaks at 470 nm), green (525 nm), and white (460 and 570 nm) lights at 0.5 W/m<SUP>2</SUP>. Rotifer reproduction is also affected by light wavelength and intensities. Asexual reproduction of rotifers is accelerated by green and red lights at 0.5 W/m<SUP>2</SUP>. On the other hand, active sexual reproduction is observed with blue light at 1.4 W/m<SUP>2</SUP>. Under a certain light condition inducing active phototactic behavior, the rotifers show continuous swimming movement without attaching to substrates. The different behaviors associated with light conditions affect the reproductive characteristics of rotifers. The regulation of live food distribution is significant for feeding efficiency of fish larvae. The efficient feeding promotes larval growth and survival: hence it is a significant factor for successful larviculture. Fish larvae also show different phototactic behavior related to light wavelengths and intensities. Therefore, the distributions of fish larvae under the applied light conditions should be considered.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rotifer eyespot efficiently absorbs light wavelength from 450 to 550 nm. </LI> <LI> Phototactic behaviors of rotifers are affected by light wavelength and intensity. </LI> <LI> Light wavelength and intensity affect population growth of rotifers. </LI> </UL> </P>

Identification of the full 26 cytochrome P450 (<i>CYP</i>) genes and analysis of their expression in response to benzo[α]pyrene in the marine rotifer <i>Brachionus rotundiformis</i>

Han, Jeonghoon,Park, Jun Chul,Hagiwara, Atsushi,Park, Heum Gi,Lee, Jae-Seong Elsevier 2019 Comparative biochemistry and physiology. Part D, G Vol.29 No.-

<P><B>Abstract</B></P> <P>Cytochrome P450s (CYPs) are a large gene superfamily that are found in all living organisms. CYPs have a key role in detoxification of xenobiotics and endogenous chemicals. Although aquatic invertebrate CYPs and their detoxification mechanisms have been reported, little is known about interspecific comparison of CYPs and their detoxification mechanism in the rotifer <I>Brachionus</I> spp. The aim of this study was to identify the entire <I>CYP</I>s in the rotifer <I>Brachionus rotundiformis</I> (<I>B</I>. <I>rotundiformis</I>) and compare <I>B</I>. <I>rotundiformis</I>-CYPs to the previously reported CYPs in other model <I>Brachionus</I> spp. (<I>B. koreanus</I>, <I>B. plicatilis</I>, and <I>B. calyciflorus</I>). To validate the model, the rotifer, specifically <I>Brachionus rotundiformis</I> was exposed to various concentrations of B[α]P, which is widely used PAH xenobiotic, and analyzed gene expression in response to B[α]P. Here, in silico analysis results showed the total of 26 <I>CYP</I>s from the rotifer <I>B. rotundiformis</I>. Based on the phylogenetic analysis, the 26 <I>B</I>. <I>rotundiformis</I>-CYPs were separated into five different clans: 2, 3, 4, mitochondrial, and 46 clans in comparison to three rotifers species, <I>B. koreanus</I>, <I>B. plicatilis</I>, and <I>B. calyciflorus</I>. To understand the detoxification mechanisms of 26 <I>B</I>. <I>rotundiformis</I>-CYPs, we investigated transcriptional expression of 26 <I>CYP</I>s and found that five <I>CYP</I>s (<I>CYP3045A2</I>, <I>CYP3045B4</I>, <I>CYP3045C10</I>, <I>CYP3049A5</I>, and <I>CYP3049E8</I>) were significantly increased (<I>P</I> < 0.05) in response to 10 and 100 μg B[α]P. In addition, we identified the aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (ARNT) and observed slight up-regulation of <I>B</I>. <I>rotundiformis</I>-<I>AhR</I> and -<I>ARNT</I>, indicating that these CYPs are likely associated with detoxification mechanism and could be used as potential molecular biomarkers of B[α]P in <I>B. rotundiformis</I>. Overall, this study will be helpful for expanding our knowledge of invertebrate CYPs on detoxification mechanisms associated with AhR signaling pathway in rotifers.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Complete mitochondrial genome of the monogonont rotifer, <i>Brachionus koreanus</i> (Rotifera, Brachionidae)

Hwang, Dae-Sik,Suga, Koushirou,Sakakura, Yoshitaka,Park, Heum Gi,Hagiwara, Atsushi,Rhee, Jae-Sung,Lee, Jae-Seong Informa UK Ltd. 2014 Mitochondrial DNA Vol.25 No.1

<P>The complete mitochondrial genome was obtained from the assembled genome data sequenced by next generation sequencing (NGS) technology from the monogonont rotifer <I>Brachionus koreanus</I>. The mitochondrial genome of <I>B. koreanus</I> was composed of two circular chromosomes designated as mtDNA-I (10,421 bp) and mtDNA-II (11,923 bp). The gene contents of <I>B. koreanus</I> were identical with previously reported <I>B. plicatilis</I> mitochondrial genomes. However, gene orders of <I>B. koreanus</I> showed one rearrangement between the two species. Of 12 protein-coding genes (<I>PCG</I>s), 3 genes (<I>ATP6, ND1</I>, and <I>ND3</I>) had an incomplete stop codon. The A + T base composition of <I>B. koreanus</I> mitochondrial genome was high (68.81%). They also showed anti-G bias (12.03% and 10.97%) on the second and third position of <I>PCG</I>s as well as slight anti-C bias (15.96% and 14.31%) on the first and third position of <I>PCG</I>s.</P>

RNA-Seq-based transcriptome profiling and expression of 16 cytochrome P450 genes in the benzo[α]pyrene-exposed estuarine copepod <i>Eurytemora affinis</i>

Lee, Bo-Young,Lee, Min-Chul,Jeong, Chang-Bum,Kim, Hee-Jin,Hagiwara, Atsushi,Souissi, Sami,Han, Jeonghoon,Lee, Jae-Seong Elsevier 2018 Comparative biochemistry and physiology. Part D, G Vol.28 No.-

<P><B>Abstract</B></P> <P>The calanoid copepod <I>Eurytemora affinis</I> is one of the most abundant estuarine species and is considered to be an ideal candidate species for ecotoxicological research. An RNA-Seq-based transcriptome was developed from whole bodies of this species. Among 142,442 contigs of the <I>de novo</I> assembly by Trinity, 48,480 open reading frame (ORF) contigs were found using TransDecoder. A total of 17,762 genes were identified by BLAST analysis, which covers about 75% of the annotated genes in the <I>E. affinis</I> genome. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that most annotated sequences were related to metabolism pathways, including xenobiotic biodegradation. Using transcriptome data, we identified putative transcripts related to xenobiotic processing genes including phase I enzymes, phase II enzymes, transporters, and transcription factors. To understand the CYP-mediated detoxification metabolism of xenobiotics, we measured the transcriptional levels of 16 CYPs (within full sequences) of <I>E. affinis</I> in response to benzo[α]pyrene (B[α]P). Most <I>Ea-CYP</I> genes were significantly down- and/or up-regulated (<I>P</I> < 0.05) in response to B[α]P, suggesting that <I>Ea-CYP</I> genes are likely involved in detoxification (mainly in biotransformation of xenobiotics) with particular genes, demonstrating significant upregulation or downregulation compared to others, as shown in other copepod model species (<I>e.g. Tigriopus japonicus</I> and <I>Paracyclopina nana</I>). This study will provide insight into the potential role of <I>E. affinis</I> in response to various toxic or xenobiotic chemicals in the marine environment.</P>

Genome-wide identification of nuclear receptor (<i>NR</i>) genes and the evolutionary significance of the NR1O subfamily in the monogonont rotifer <i>Brachionus</i> spp.

Kim, Duck-Hyun,Kim, Hui-Su,Hwang, Dae-Sik,Kim, Hee-Jin,Hagiwara, Atsushi,Lee, Jae-Seong,Jeong, Chang-Bum Academic Press 2017 General and comparative endocrinology Vol.252 No.-

<P><B>Abstract</B></P> <P>Nuclear receptors (NRs) are a large family of transcription factors that are involved in many fundamental biological processes. NRs are considered to have originated from a common ancestor, and are highly conserved throughout the whole animal taxa. Therefore, the genome-wide identification of <I>NR</I> genes in an animal taxon can provide insight into the evolutionary tendencies of NRs. Here, we identified all the <I>NR</I> genes in the monogonont rotifer <I>Brachionus</I> spp., which are considered an ecologically key species due to their abundance and world-wide distribution. The NR family was composed of 40, 32, 29, and 32 genes in the genomes of the rotifers <I>B</I>. <I>calyciflorus</I>, <I>B. koreanus</I>, <I>B. plicatilis</I>, and <I>B. rotundiformis</I>, respectively, which were classified into seven distinct subfamilies. The composition of each subfamily was highly conserved between species, except for <I>NR1O</I> genes, suggesting that they have undergone sporadic evolutionary processes for adaptation to their different environmental pressures. In addition, despite the dynamics of NR evolution, the significance of the conserved endocrine system, particularly for estrogen receptor (ER)-signaling, in rotifers was discussed on the basis of phylogenetic analyses. The results of this study may help provide a better understanding the evolution of NRs, and expand our knowledge of rotifer endocrine systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fourty, 32, 29, and 32 <I>NR</I> genes were identified in the four rotifer <I>Brachionus</I> spp. </LI> <LI> Species-specific evolution of <I>NR1O</I> genes was identified. </LI> <LI> The evolutionary scenario of ER-signaling pathways in <I>Brachionus</I> spp. have speculated on the basis of our phylogenetic analysis. </LI> </UL> </P>

Effects of metal-polluted seawater on life parameters and the induction of oxidative stress in the marine rotifer <i>Brachionus koreanus</i>

Jeong, Chang-Bum,Lee, Young Hwan,Park, Jun Chul,Kang, Hye-Min,Hagiwara, Atsushi,Lee, Jae-Seong PERGAMON PRESS 2019 COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C Vol.225 No.-

<P><B>Abstract</B></P> <P>Metal pollution is one of the major threats to the aquatic environment due to its high bio-concentrations and toxicity. Although numerous studies have been conducted to understand detoxification and toxicity mechanisms in aquatic invertebrates, most of them were limited in laboratory study. Here, we investigated adverse effects of the contaminated-natural seawater on the marine rotifer <I>Brachionus koreanus</I>. Field seawater was collected from five different sites of Youngil Bay, South Korea where pollution by metals is predicted due to industrial discharges from nearby steel industry complexes. The marine rotifer <I>B. koreanus</I> was exposed to different seawater samples, and we found decreased population growth rates with highly induced transcriptional level of detoxification-related genes. Our finding shows a link between the induction of metal-mediated regulation of detoxification genes in <I>B. koreanus</I> and concentration of heavy metals present in various seawater samples, implying those biomarker genes can be useful to assess the toxicity of metal polluted natural seawaters. Our results are helpful to validate and establish biomarker genes for early risk assessment of metal contamination in the natural sea water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ICP-MS analysis revealed the presence of nickel, copper, zinc, and lead in Youngil Bay, South Korea. </LI> <LI> Decreased population growth rates were shown in <I>B. koreanus</I> upon seawater exposures. </LI> <LI> Detoxification-related genes were highly induced upon seawater exposures. </LI> <LI> The induction of detoxification genes was correlated with concentration of heavy metals in various seawaters. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The genome of the marine monogonont rotifer <i>Brachionus plicatilis</i>: Genome-wide expression profiles of 28 cytochrome P450 genes in response to chlorpyrifos and 2-ethyl-phenanthrene

Han, Jeonghoon,Park, Jun Chul,Choi, Beom-Soon,Kim, Min-Sub,Kim, Hui-Su,Hagiwara, Atsushi,Park, Heum Gi,Lee, Bo-Young,Lee, Jae-Seong Elsevier 2019 Aquatic toxicology Vol.214 No.-

<P><B>Abstract</B></P> <P> <I>Brachionus</I> spp. (Rotifera: Monogononta) are globally distributed in aquatic environments and play important roles in the aquatic ecosystem. The marine monogonont rotifer <I>Brachionus plicatilis</I> is considered a suitable model organism for ecology, evolution, and ecotoxicology. In this study, we assembled and characterized the <I>B. plicatilis</I> genome. The total length of the assembled genome was 106.9 Mb and the number of final scaffolds was 716 with an N50 value of 1.15 Mb and a GC content of 26.75%. A total of 20,154 genes were annotated after manual curation. To demonstrate the use of whole genome data, we targeted one of the main detoxifying enzyme of phase I detoxification system and identified in a total of 28 cytochrome P450 s (CYPs). Based on the phylogenetic analysis using the maximum likelihood, 28 <I>B. plicatilis</I>-CYPs were apparently separated into five different clans, namely, 2, 3, 4, mitochondrial (MT), and 46 clans. To better understand the CYPs-mediated xenobiotic detoxification, we measured the mRNA expression levels of 28 <I>B. plicatilis CYP</I>s in response to chlorpyrifos and 2-ethyl-phenanthrene. Most <I>B. plicatilis CYP</I>s were significantly modulated (<I>P</I> < 0.05) in response to chlorpyrifos and 2-ethyl-phenanthrene. In addition, xenobiotic-sensing nuclear receptor (XNR) response element sequences were identified in the 5 kb upstream of promoter regions of 28 <I>CYP</I>s from the genome of <I>B. plicatilis</I>, indicating that these XNR can be associated with detoxification of xenobiotics. Overall, the assembled <I>B. plicatilis</I> genome presented here will be a useful resource for a better understanding the molecular ecotoxicology in the view of molecular mechanisms underlying toxicological responses, particularly on xenobiotic detoxification in this species.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The total length of the assembled genome was 106.9 Mb with an N50 value of 1.15 Mb. </LI> <LI> A total of 20,154 genes were annotated after manual curation. </LI> <LI> 28 <I>B. plicatilis</I>-CYPs were apparently separated into 2, 3, 4, mitochondrial (MT), and 46 clans. </LI> <LI> Most <I>B. plicatilis CYP</I>s were significantly modulated (<I>P</I> < 0.05) in response to chlorpyrifos and 2-ethyl-phenanthrene. </LI> <LI> XNR response element sequences were identified in the 5 kb upstream of promoter regions of 28 <I>CYP</I>s. </LI> </UL> </P>

Lipid metabolism modulation by five different food types in the monogonont marine rotifer <i>Brachionus koreanus</i>

Lee, Min-Chul,Park, Jun Chul,Yoon, Deok-Seo,Choi, Hyuntae,Shin, Kyung-Hoon,Kim, Hee-Jin,Hagiwara, Atsushi,Lee, Jae-Seong Elsevier 2019 Aquaculture Vol.503 No.-

<P><B>Abstract</B></P> <P>To investigate the effects of five different foods on fatty acid metabolism in the monogonont marine rotifer <I>Brachionus koreanus</I>, we measured life cycle parameters, analyzed the area of Nile red staining, fatty acid composition, and mRNA expression of fatty acid desaturase (<I>Fads</I>) and elongation of very long chain fatty acid (<I>Elovl</I>) genes. Among the five different foods (<I>Tetraselmis suecica</I>, <I>Chlorella</I> sp., <I>Isochrysis galbana</I>, <I>Chaetoceros</I> sp., and <I>Nannochloropsis oculata</I>), life span of <I>I. galbana</I>-fed group was significantly increased compared to the other groups. However, the reproduction parameters (cumulative offspring and daily reproduction) were the highest in <I>T. suecica</I>-fed group, and the lowest in <I>Chlorella</I> sp.-fed group. The area of Nile red staining analysis showed similar trends, in respect to the content of total fatty acid. The single fatty acid analysis result clearly indicated that not only the most of the content of fatty acid was highly dependent on the food types, especially in omega-6 fatty acids group, but also, <I>B. koreanus</I> could newly synthesize some specific fatty acids by themselves (e.g. omega-3 and -9 families). Lastly, the mRNA expression of <I>Elovl</I> and <I>Fads</I> genes were modulated by food types indicating the lipid metabolism could be controlled by food in <I>B. koreanus</I> and probably very small amount of 18:3n-3 fatty acids was utilized and synthesized omega-3 fatty acids through the increase in <I>Elovl</I> and <I>Fads</I> gene expression in <I>Chaetoceros</I> sp. and <I>N. oculata</I>-fed groups. In conclusion, this study revealed that although <I>B. koreanus</I> could modulate fatty acid metabolism by itself, some nutrient values (e.g. omega-6 fatty acids) should be considered, therefore, it is important to understand the essential nutrient through both the molecular and quantitative analysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Among the five types of foods, life span of <I>Isochrysis galbana</I>-fed group was significantly increased compared to other groups. </LI> <LI> The reproduction parameters were the highest in <I>T. suecica</I>-fed group, and the lowest in <I>Chlorella</I> sp.-fed group. </LI> <LI> The most of the content of fatty acid was highly dependent on the food types, especially in omega-6 fatty acids group. </LI> <LI> <I>B. koreanus</I> could newly synthesize some specific fatty acids by themselves (e.g. omega-3 and -9 families). </LI> <LI> The mRNA expression of <I>Elovl</I> and <I>Fads</I> genes were modulated by food types indicating the lipid metabolism could be controlled by food in <I>B. koreanus</I>. </LI> </UL> </P>

Genome-wide identification of 31 cytochrome P450 (<i>CYP</i>) genes in the freshwater rotifer <i>Brachionus calyciflorus</i> and analysis of their benzo[α]pyrene-induced expression patterns

Han, Jeonghoon,Kim, Duck-Hyun,Kim, Hui-Su,Kim, Hee-Jin,Declerck, Steven A.J.,Hagiwara, Atsushi,Lee, Jae-Seong Elsevier 2018 Comparative biochemistry and physiology. Part D, G Vol.25 No.-

<P><B>Abstract</B></P> <P>While marine invertebrate cytochrome P450 (CYP) genes and their roles in detoxification mechanisms have been studied, little information is available regarding freshwater rotifer CYPs and their functions. Here, we used genomic sequences and RNA-seq databases to identify 31 <I>CYP</I> genes in the freshwater rotifer <I>Brachionus calyciflorus</I>. The 31 <I>Bc-CYP</I> genes with a few tandem duplications were clustered into CYP 2, 3, 4, mitochondrial, and 46 clans with two marine rotifers <I>Brachionus plicatilis</I> and <I>Brachionus koreanus</I>. To understand the molecular responses of these 31 <I>Bc-CYP</I> genes, we also examined their expression patterns in response to benzo[α]pyrene (B[α]P). Three <I>Bc-CYP</I> genes (<I>Bc-CYP3044B3</I>, <I>Bc-CYP3049B4</I>, <I>Bc-CYP3049B6</I>) were significantly upregulated (<I>P</I> <0.05) in response to B[α]P, suggesting that these <I>CYP</I> genes can be involved in detoxification in response to B[α]P exposure. These genes might be useful as biomarkers of B[α]P exposure in <I>B. calyciflorus</I>. Overall, our findings expand the repertoire of known CYPs and shed light on their potential roles in xenobiotic detoxification in rotifers.</P>