D3136: Comparative study of the coat proteins of cotton leafroll dwarf virus-AL P3/P3-5 to different Poleroviruses

Transmitted by the cotton/melon aphid, Aphis gossypii, Cotton leafroll dwarf virus (CLRDV), first reported in Alabama in 2017, is a serious disease in cotton. CLRDV is a Polerovirus in the family Solemoviridae which encodes seven genes. Unable to use mechenical transmission, these viruses undergo transcytosis in gut epithelial cells of the aphid and these viruses are not thought to replicate in their vector. There are two surface proteins in poleroviruses, P3 and P3-5, encoded on a subgenomic RNA. A preliminary study on the protein and nucleotide sequences of P3 and P3-5 of CLRDV_AL(MN071395.1) across the range of poleroviruses was conducted. The amino acid sequences of P3 of CLRDV_AL are more similar (80% identity) to the Brassica yellows virus (transmitted by Myzus persicae) and distantly related to Suakwa aphid-borne yellows virus (45% identity) whereas P3-5 sequences is in the range of 17% to 57% identity respectively with virus Brassica yellows virus and Suakwa aphid-borne yellows virus (also transmitted by Aphis gossypii). To determine localization of the P3 and P3-5 proteins in insect cells, a fusion to GFP and RFP was constructed for expression in Sf9 cells. We observed that P3 is expressed in the nucleus of insect cells, surprising as it does not have a nuclear localization signal. The finding of this study is the first step in determining which insect proteins interact with the viral capsid protein of poleroviruses including CLRDV, which could be novel control mechanism to find a barrier for vector transmission by aphids.