Molecular insights into the mechanisms of susceptibility of Labeo rohita against oomycete Aphanomyces invadans

P K Pradhan,Vindhya Mohindra,Neeraj Sood,Chris Hauton,Kenton L Morgan,Syed Assim Haq,Shubham Gupta,Pieter Van West,Franziska Trusch,Sergei V Shubin,Luca Peruzza,Dev Kumar Verma

doi:10.1038/s41598-020-76278-w

Abstract

Aphanomyces invadans, the causative agent of epizootic ulcerative syndrome, is one of the most destructive pathogens of freshwater fishes. To date, the disease has been reported from over 160 fish species in 20 countries and notably, this is the first non-salmonid disease that has resulted in major impacts globally. In particular, Indian major carps (IMCs) are highly susceptible to this disease. To increase our knowledge particularly with regards to host immune response against A. invadans infection in a susceptible host, the gene expression profile in head kidney of A. invadans-infected and control rohu, Labeo rohita was investigated using RNA sequencing. Time course analysis of RNA-Seq data revealed 5608 differentially expressed genes, involved among others in Antigen processing and presentation, Leukocyte transendothelial migration, IL-17 signaling, Chemokine signaling, C-type lectin receptor signaling and Toll-like receptor signaling pathways. In the affected pathways, a number of immune genes were found to be downregulated, suggesting an immune evasion strategy of A. invadans in establishing the infection. The information generated in this study offers first systematic mechanistic understanding of the host–pathogen interaction that might underpin the development of new management strategies for this economically devastating fish-pathogenic oomycete A. invadans.

Highlights

Aphanomyces invadans, the causative agent of epizootic ulcerative syndrome, is one of the most destructive pathogens of freshwater fishes
Time course analysis of RNA sequencing (RNA-Seq) data generated from head kidney of rohu challenged with A. invadans revealed 5608 differentially expressed genes, of which, 390 genes were involved in 21 immune-related pathways
Most of the differentially expressed immune genes were related to Antigen processing and presentation, Leukocyte transendothelial migration, Chemokine signaling, IL-17 signaling, C-type lectin receptor signaling and Toll-like receptor signaling pathways

Summary

Introduction

Aphanomyces invadans, the causative agent of epizootic ulcerative syndrome, is one of the most destructive pathogens of freshwater fishes. To increase our knowledge with regards to host immune response against A. invadans infection in a susceptible host, the gene expression profile in head kidney of A. invadans-infected and control rohu, Labeo rohita was investigated using RNA sequencing. Comparison of RNA sequences from infected and uninfected samples gives insights into immune-related genes that are differentially expressed during an infection, and lead to a better understanding of molecular mechanisms involved in host immunity to a particular pathogen[18]. Majority of key genes in Antigen processing and presentation and Toll-like receptor signaling pathway were found to be downregulated, which suggested an immune evasion strategy of A. invadans. The information generated in this study would provide novel insights into host defence mechanisms that are affected following A. invadans infection and will serve as knowledge base and platform for developing future novel disease control measures

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