In silico analysis of PirA- and PirB-like toxin genes of Vibrio spp., present in Asia and Costa Rica

Arren Guia,Mary Uy,Jaypee Samson

doi:10.5455/javar.2020.g424

Abstract

Objective:Acute hepatopancreatic necrosis disease is an emerging infectious disease of Penaeus species. The causative agent is Vibrio species, which dispels binary toxin similar to pirA and pirB, which causes mortality in infected shrimp. The aim of this research was to investigate the evolutionary relationship of pirA and pirB homologous genes present in this Asia and Costa Rica in silico.Materials and methods:The sequences for in silico analysis were all retrieved from the Basic Local Alignment Search Tool Nucleotide (BLASTN) tool of the National Center for Biotechnology Center. For pirA, a total of 25 sequences submitted from different Asian countries and Costa Rica were retrieved for analysis. Meanwhile, for pirB, a total of 11 sequences submitted from five Asian countries were retrieved. Sequences were aligned using the CLUSTAL W alignment tool under Molecular Evolutionary Genetics Analysis (MEGA) 7 software. The evolutionary history was then estimated using the Unweighted Pair Group Method with Arithmetic mean (UPGMA) method, whereas the evolutionary distances were determined using the maximum composite likelihood model with 1,000 bootstrap replications.Results and Discussion:The results show that, among 27 DNA sequences analyzed for pirA gene, three groups were generated, while for pirB, 13 DNA sequences yielded only one group. The analysis revealed low genetic variation among isolates for both pirA and pirB genes.Conclusion:This result suggests that the low frequency of polymorphism and geographic location cannot be attributed to the differences in V. parahaemolyticus isolates in Asian countries relative to Costa Rican isolates in pirA and pirB genes.

Highlights

The acute hepatopancreatic necrosis disease (AHPND, formerly known as early mortality syndrome) has reportedly been the cause of high mortalities and production in Southeast Asian countries
This result suggests that the low frequency of polymorphism and geographic location cannot be attributed to the differences in V. parahaemolyticus isolates in Asian countries relative to Costa Rican isolates in pirA and pirB genes
Asian and Costa Rican isolates were grouped together for pirA gene despite differences in geographic location, corroborating with the previous studies that toxin genes such as pirA and pirB exhibit low polymorphism. This result only suggests that the low frequency of polymorphism and geographic location cannot be attributed to the differences in V. parahaemolyticus isolates in Asian countries relative to Costa Rican isolates in pirA gene

Summary

Introduction

The acute hepatopancreatic necrosis disease (AHPND, formerly known as early mortality syndrome) has reportedly been the cause of high mortalities and production in Southeast Asian countries. It induces necrosis in the hepatopancreas of the diseased shrimp, which is caused by the bacterium Vibrio species [1]. Histological sections of the hepatopancreas of Penaeus vannamei (Fig. 1A and B) show the differences between the hepatopancreas of normal and infected shrimps. AHPND lesions are present (Fig. 1B) through the immense sloughing of hepatopancreatic tubule epithelial cells into the lumen, which only suggests severe necrosis marked by cellular detachment relating to a bacterial infection. Several studies illustrate that the genomes of these pathogenic isolates possess genes, which are homologous with the Photorhabdus insect-related (Pir) toxin genes pirA and pirB [3]

Methods

Results

Conclusion