Molecular characterization of emaraviruses associated with Pigeonpea sterility mosaic disease

Surender Kumar,B L Subbarao,Vipin Hallan

doi:10.1038/s41598-017-11958-8

Abstract

Sterility Mosaic Disease (SMD) of pigeonpea (Cajanus cajan (L.) Millspaugh) is a complex disease due to various factors including the presence of a mixed infection. Comparison of dsRNA profile and small RNA (sRNA) deep sequencing analysis of samples from three locations revealed the presence of Pigeonpea sterility mosaic virus-I and II (PPSMV-I and II) from Chevella and only PPSMV-II from Bengaluru and Coimbatore. PPSMV-I genome consisted of four while PPSMV-II encompassed six RNAs. The two viruses have modest sequence homology between their corresponding RNA 1–4 encoding RdRp, glycoprotein precursor, nucleocapsid and movement proteins and the corresponding orthologs of other emaraviruses. However, PPSMV-II is more related to Fig mosaic virus (FMV) than to PPSMV-I. ELISA based detection methodology was standardized to identify these two viruses, uniquely. Mite inoculation of sub-isolate Chevella sometimes resulted in few- to- many pigeonpea plants containing PPSMV-I alone. The study shows that (i) the N-terminal region of RdRp (SRD-1) of both the viruses contain “cap-snatching” endonuclease domain and a 13 AA cap binding site at the C-terminal, essential for viral cap-dependent transcription similar to the members of Bunyaviridae family and (ii) P4 is the movement protein and may belong to ‘30 K superfamily’ of MPs.

Highlights

Pigeonpea sterility mosaic is a major disease of pigeonpea [Cajanus cajan (L.) Millspaugh] in the Indian subcontinent
All emaraviruses reported till date have virus particles as quasi to spherical with double lipid membrane-bound particles containing four (EMARaV, Rose rosette virus RRV and PPSMV-I in this study), six (Fig mosaic virus FMV, PPSMV-II in this study) and eight (WMoV, Raspberry leaf blotch virus RLBV) segmented negative sense RNAs encapsulated in nucleocapsid and transmitted by eriophyid mites belonging to different
Positive signals for detection of both PPSMVs nucleocapsid proteins (NCP) was detected only in plants infected by sub-isolate Chevella (Fig. S10, slots 1 and 2 of upper and lower rows in the blot), confirming the presence of both viruses in PPSMV-P sub-isolate Chevella, whereas nucleocapsid protein of PPSMV-II alone was detected in the plants infected by PPSMV-B and PPSMV-C isolates

Summary

Introduction

Pigeonpea sterility mosaic is a major disease of pigeonpea [Cajanus cajan (L.) Millspaugh] in the Indian subcontinent. All emaraviruses reported till date have virus particles as quasi to spherical with double lipid membrane-bound particles containing four (EMARaV, Rose rosette virus RRV and PPSMV-I in this study), six (Fig mosaic virus FMV, PPSMV-II in this study) and eight (WMoV, Raspberry leaf blotch virus RLBV) segmented negative sense RNAs encapsulated in nucleocapsid and transmitted by eriophyid mites belonging to different www.nature.com/scientificreports/. PPSMVs share similarities with other emaraviruses in their genomic organization and conserved 5′ and 3′-end sequences, additional non-conserved RNA segments (in PPSMV-II) which encode nucleocapsid proteins (NCP) to facilitate genome encapsidation, with over all limited sequence homology and eriophyid mite transmission Plant viruses with these traits have been grouped to an unassigned genus Emaravirus[21], other members of this genus includes EMARaV the type member of this genus[22], FMV23–25, RRV26, RLBV17,27, WMoV14, RYRSaV18, AcCRaV19, and WBYVV20

Methods

Results

Conclusion