Modulation of NPV gene expression pattern and retention of RNAi- based antiviral activity in inbred transgenic silkworm
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ORIGINAL RESEARCH ARTICLE
Modulation of NPV gene expression pattern and retention of RNAi- based antiviral activity in inbred transgenic silkworm Burdekar Varada 1 & Appukuttan Nair R. Pradeep 1 & Arvind K. Awasthi 1 & Kangayam M. Ponnuvel 1 Accepted: 30 August 2018 # African Association of Insect Scientists 2020
Abstract Infections due to Bombyx mori nucleopolyhedro virus (BmNPV) in commercially important silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) causes up to 50% loss to silk production in India. Increased resistance to NPV through introduction of double stranded RNA transgenes against multiple NPV genes is reported in B. mori. However, stability of the RNAi - mediated antiviral activity has not been determined after several generations of inbred transgenic B. mori. Hence, we examined the NPV multiplication rate and induction of the disease symptoms in NPV- infected transgenic and non-transgenic silkworm after 35 generations. Significantly higher multiplication rate of NPV supported by higher copy number of gp-41 gene was observed in non- transgenic larvae as compared to transgenic larvae. Expression of NPV genes, ie-1, lef1 and p74 enhanced significantly in non-transgenic larva as compared to transgenic larva after NPV infection. Strong positive correlation was observed in the expression pattern of NPV genes in transgenic larvae which was absent in non-transgenic larvae. This indicated co-regulation of NPV gene expression in the presence of transgenes. Keywords Bombyx mori . NPV tolerance . Transgenic silkworm . RNA interference . NPV genes . Inbreeding
Introduction The Lepidopteran larvae are infected specifically by viruses of Bacculoviridae family (Cory and Myers 2003). Bombyx mori NPV (BmNPV) infection is highly specific to the silkworm Bombyx mori L.1758 (Lepidoptera : Bombycidae). Most of the high yielding races of B. mori are highly susceptible to infection by NPV. Recently NPV resistance was enhanced in B. mori Nistari race larvae by introducing double stranded RNA against single or multiple genes that regulate NPV multiplication. The dsRNA was introduced by transgenesis through germline transformation (Kanginakudru et al. 2007; Subbaiah et al. 2013). Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42690-020-00201-z) contains supplementary material, which is available to authorized users. * Appukuttan Nair R. Pradeep [email protected] 1
Proteomics Division, Seribiotech Research Laboratory, CSBKodathi Campus, Carmelaram Post, Bangalore 560035, Karnataka, India
The piggyBac-inserted sequences encompass segments of four BmNPV genes, immediate early-1 gene (ie1), late expression factor-1 (lef1), lef3 and per os infectivity factor gene (p74) and coding region for marker red or green fluorescent protein (Subbaiah et al. 2013). This transgenic improvement is a selective method to control NPV multiplication in B. mori (Zhang et al. 2014; Jiang and Xia 2014). It is known that ‘tolerance’ to parasitic infection including NPV is a polygenically contr
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