Comparison of five commercial kits for isolation of total RNA in samples of WSSV-infected shrimp

Viral diseases are the most serious threat to the expansion and development of shrimp aquaculture. Rapid diagnosis of the white spot syndrome virus (WSSV), a lethal shrimp pathogen, is essential to restrict its spread and reduce the mortality of infected shrimp. This virus has globally affected the shrimp farming industry, with a devastating economic impact. Several studies have focused on the expression of WSSV transcripts to understand the molecular mechanisms governing the pathological development of the disease. Since gene expression studies and molecular diagnostics at the early stages of infection depend on the efficient isolation of high-quality RNA, the extraction methods should be carefully selected. However, previous comparisons of the performance of RNA isolation kits have yet to be systematically investigated. In this study, 5 commercial RNA extraction methods were compared in WSSV-infected shrimp. The highest total RNA yield (ng mg-1 tissue) was obtained using TRIzol. Even though the 260/280 nm absorption ratios showed significant differences, the methods showed good purity values (>2.0). RNA integrity was evaluated in a denaturing agarose gel electrophoresis, and degradation was observed after the total RNA samples were treated with DNase I. Finally, the method that allowed the earlier detection of WSSV transcripts by qRT-PCR was the Zymo Direct-zol RNA MiniPrep kit. This study shows that the amount of observed (or estimated) WSSV transcripts might be affected because of the RNA isolation method. In addition, these results may contribute to improve the accuracy of the results obtained in gene expression studies, for more sensitive and robust detection of WSSV.