Published online October 24, 2022
Journal of Ecology and Environment (2022) 46:27
Jongsun Kim1† , Nam-Ho Roh2† , Jaejin Park1 and Daesik Park1*
1Division of Science Education, Kangwon National University, Chuncheon 24341, Republic of Korea
2Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Republic of Korea
Correspondence to:Daesik Park
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Ranaviruses are a primary cause of amphibian extinctions. More consistent ranavirus-infection reports and genetic characterizations of identified viruses are urgently needed, particularly from Asian countries. The objectives of this study were to obtain the partial major capsid protein (MCP) gene sequences (506 bp) of the ranavirus responsible for infecting frogs in South Korea, as our previous research had confirmed using qPCR, and to evaluate their genetic relationships with other previously reported ranavirus sequences. Three different ranavirus MCP sequences were obtained from Pelophylax nigromaculatus and Lithobates catesbeianus. All six different types of MCP sequence from the ranavirus identified in South Korea to date belonged to the Frog virus 3 (FV3)-like virus group in the genus Ranavirus. To better understand the origin and spread of ranaviruses in South Korea, further infection reports and full genome analyses of the identified ranaviruses are needed.
Keywords: Asia, frog virus 3, infectious disease, Iridoviridae
Ranaviruses in the genus
Recently, ranavirus-related research has increased in Asia, where research has been needed. Although most studies have been conducted in China, ranavirus-induced mass amphibian mortalities have also been reported in Japan, Taiwan, Korea, Malaysia, India, and Russia (Hazeri et al. 2017; Herath et al. 2021; Huang et al. 2011; Hsieh et al. 2021; Lisachov and Lisachova 2022; Mu et al. 2018; Sivasankar et al. 2017; Une et al. 2009; Xu et al. 2010). The first South Korean ranavirus-induced mass mortality was confirmed in 2009 involving larval gold-spotted pond frogs (
The purposes of this study were to obtain the partial MCP sequences of the ranavirus that infects black-spotted pond frogs (
For this study, we selected larvae of
To amplify the partial MCP gene (500 bp), we used MCP4 and MCP5 primers, as used in our previous studies (Kwon et al. 2017; Mao et al. 1997; Park et al. 2021). We conducted PCR in a total volume of 20
We checked the resulting MCP sequences using Geneious Prime (Biomatters Ltd, Auckland, New Zealand). To examine the genetic relationship between the verified ranavirus types in this study and other previously known ranaviruses, we performed Basic Local Alignment Search Tool (BLAST) analysis and constructed a phylogenetic tree. For the custom nested BLAST analysis, we downloaded 39 partial MCP sequences of representative ranaviruses from the GenBank, such as the viruses previously reported from South Korea, including FV3-like viruses, CMTV-like viruses, and ATV-like viruses, and aligned the sequences using the default setting of MUSCLE (multiple sequence comparison by log‐expectation) (Edgar 2004). We performed BLAST using Geneious Prime (Biomatters Ltd). For the lineage-based genetic relationship analysis, we constructed a Bayesian inference (BI) tree using the Markov chain Monte Carlo (MCMC) methods in MrBayes v3.2.4 (Ronquist et al. 2012). We ran 60 million tree generations, starting with a random tree, while saving every 1,000th tree into a file and discarding the first 5% of the sampled generations as burn-ins. For the analysis, we included 44 ranavirus MCP sequences, which were used for the BLAST, and the MCP sequence of short-finned eel ranavirus (FJ358612) was used as an outgroup.
Among the ten tadpoles that we previously analyzed to confirm ranavirus infection in a previous study (Roh et al. 2022), we successfully obtained partial sequences (506 bp) of ranavirus MCP gene from four of the
In the BLAST analysis, Type A sequence showed 99.6% similarity with KRV-1 from South Korea (HM133594), Rana catesbeiana virus from Japan (AB474588), and Rana grylio iridovirus from China (JQ654586), and Type C sequence showed 100% similarity with these three virus types. Type B sequence showed 100% similarity with FV3 (MH332773, KF646249, MF360246, and MF411070) reported in Canada, the United States, the Netherlands, and the United Kingdom and with Lacerta monticola ranavirus (KM516719) reported in Portugal. The similarity between the three MCP sequence types in this study and the two types (KY264204-5), which were previously reported from two mountain frog species (
In this study, we successfully obtained the partial MCP gene sequence of the ranavirus from four
Ranaviruses belonging to the FV3-like virus group in the genus
All six types of ranavirus MCP sequence reported in Korean amphibians to date belong to the FV3-like virus group with genetic variations. According to previous studies, genetic variations in FV3-like viruses occur frequently (Stöhr et al. 2015), caused by either genetic recombination between viruses of different strains or the process of adapting to different hosts and environments over time (Cronin et al. 2010; Grant et al. 2019; Vilaça et al. 2019). Regarding the possibility of interspecies genetic recombination, evaluation is not currently possible in South Korea. Unfortunately, studies on iridoviruses have not been conducted in other ectothermic organisms that cohabitate with amphibians. The genetic variations in FV3-like viruses due to the adaptation process may be applicable to our results. In this study, various types of ranavirus MCP sequence, within the FV3-like virus group, tended to differ according to host species and collection region. For example, virus MCP sequence types identified from
In this study, we confirmed ranavirus infection in two more anuran species (
We thank Woo-Jin Choi, Il-Kook Park, Ji-Ho Park for their help during field sampling and MinWoo Park, Ho-Jun Jung for their help during the dissection.
ATV: Ambystoma tigrinum virus
BI: Bayesian inference
BLAST: Basic Local Alignment Search Tool
CMTV: Common midwife toad virus
CT: Cycle threshold
FV3: Frog virus 3
MCMC: Markov chain Monte Carlo
MCP: Major Capsid Protein
JK did data curation, formal analysis, investigation, and writing-original draft. NHR did data curation, investigation, formal analysis, and writing-review and editing. JP and DP did conceptualization, funding acquisition, supervision, writing-original draft, and writing-review and editing.
This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2020R1A6A3A1306094911).
All data generated or analyzed during this study are included in this published article.
This study was reviewed and approved by the Institutional Animal Care and Use Committee of Kangwon National University (KW-200618-3).
The authors declare that they have no competing interests.
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Short communication 2023-05-10 46:04High ranavirus infection rates at low and extreme temperatures in the tadpoles of Japanese treefrogs (Dryophytes japonicus) that breed in rice paddies in the summer
Nam-Ho Roh1#, Jongsun Kim2#, Jaejin Park2 and Daesik Park2*