Identification of the RNA silencing suppressor activity of sugarcane streak mosaic virus P1 gene

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ORIGINAL ARTICLE

Identification of the RNA silencing suppressor activity of sugarcane streak mosaic virus P1 gene Krishnamoorthy Bagyalakshmi1 • Rasappa Viswanathan1

Received: 11 May 2020 / Accepted: 25 July 2020  Indian Virological Society 2020

Abstract Sugarcane streak mosaic virus (SCSMV) belonging to Poacevirus, is a causative virus of mosaic disease in sugarcane in many Asian countries with substantial genomic variation. Although the virus infects the crop with Sugarcane mosaic virus (SCMV) a Potyvirus, it predominates over SCMV in spread as well as titre. We have taken up detailed studies to identify the functional activity of viral suppressors of SCSMV genome. Transient expression assay was performed with SCSMV-P1 and HCPro genes in the model plant Nicotiana tabacum to establish suppressor role of these genes. The plasmid constructs of both the genes were co-infiltrated with the reporter green fluorescent protein (GFP) and the suppressor activity was measured as enhancement in the GFP fluorescence. Further, the phenotypic expressions were validated by respective gene expression through semi quantitative and qRT-PCR. In the P1 co-infiltrated GFP leaves, suppression in the PTGS mechanism took place that allowed a long term expression of GFP. However, GFP co-infiltrated with HC-Pro did not sustain the GFP expression level for a prolonged period and the expression level was close to GFP control. The study concluded that unlike in other Potyviridae genera, P1 gene of SCSMV is playing the role of RNA silencing suppressor. This study helps in unveiling a new and promising way to understand the regulatory

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13337-020-00618-7) contains supplementary material, which is available to authorized users. & Rasappa Viswanathan [email protected] 1

Division of Crop Protection, Indian Council of Agricultural Research - Sugarcane Breeding Institute, Coimbatore 641007, India

pathway in the host at the time of viral infection. Targeting the P1 gene of SCSMV through RNA silencing approach will be a viable strategy to develop mosaic resistant transgenic sugarcane varieties as they are directly involved in counter defence against the host. Keywords Sugarcane streak mosaic virus  RNA silencing suppressor  HC-Pro  P1  Silencing assay

Introduction Most eukaryotes, including plants, make use of a wellconserved RNA silencing mechanism to regulate many essential biological processes, ranging from development and control of physiological activities, to off-set different abiotic and biotic stresses and in particular antiviral defense. The research on this area has been intensely investigated for fundamental reasons and also because of its potential application for crop improvement [19]. A fascinating feature of RNA silencing in plants is that after initiation of local silencing, a signal is produced that can move between cells through plasmodesmata and over long distance through the vascular system to direct specific RNA silenc