A Single Banana Streak Virus Integration Event in the Banana Genome as the Origin of Infectious Endogenous Pararetrovirus

Abstract

Sequencing of plant nuclear genomes reveals the widespread presence of integrated viral sequences known as endogenous pararetroviruses (EPRVshowever, only one allele is infectious. Analysis of BSGfV EPRV segregation among an F1 population from an interspecific genetic cross revealed that these EPRV sequences correspond to two alleles originating from a single integration event. We describe here for the first time the full genomic and genetic organization of the two EPRVs of BSGfV present in cv. PKW in response to the challenge facing both scientists and breeders to identify and generate genetic resources free from BSV. We discuss the consequences of this unique host-pathogen interaction in terms of genetic and genomic plant defenses versus strategies of infectious BSGfV EPRVs.

Evasion of Short Interfering RNA-Directed Antiviral Silencing in Musa acuminata Persistently Infected with Six Distinct Banana Streak Pararetroviruses

“…This is the case in the banana A genome, which contains multiple integrants of badnavirus-like sequences, but those contain only incomplete, highly rearranged, and fragmented genomes that exhibit distant similarity to the infectious BSV species described to date, limiting the possibility of giving rise to episomal virus infections (22,40,42,43). In contrast, more recent BSV integrants in the B genome, including BSOLV (44), Banana streak Goldfinger virus (BSGFV) (45), Banana streak Imove virus (BSIMV) (41,46), and, likely, Banana streak Mysore virus (BSMYV) (27) In this study, we characterized the sRNA-generating silencing machinery in persistently infected banana plants and examined whether or not episomal pararetroviruses are able to evade siRNA-directed DNA methylation. We used rolling circle amplification (RCA) and sequencing of viral DNA combined with sRNA deep sequencing to reconstruct the complete genomes and siRNA profiles for six episomal BSV species (BSOLV, BSGFV, BSIMV, BSMYV, BSVNV, and BSCAV) that persisted in M. acuminata triploid (AAA) banana plants over 10 years of vegetative propagation following transmission by mealybugs.…”

Molecular analysis of gooseberry vein banding associated virus

“…Their infection can lead to development of flecks, freckles, streaks, chlorosis or yellowing along veins, or there may be no visible symptoms whatsoever. In the past decade, badnaviruses have been the subject of increased attention since the discovery of their endogenous sequences in various plant genomes (Geering et al, 2005(Geering et al, , 2011Gayral et al, 2008;Kenyon et al, 2008;Bousalem et al, 2009;James et al, 2011) and risk of their putative spread through infected germplasm and/or activation by an abiotic stress during propagation (Dallot et al, 2001).…”

Three Infectious Viral Species Lying in Wait in the Banana Genome

“…BACs containing eBSGFV were obtained from GenBank (accession numbers AP009325 and AP009326, corresponding to MBP_71C19 and MBP_94I16, respectively [13]). BAC MBP_31007 containing eBSOLV was obtained from GenBank (accession number AP009334).…”

“…inflata and Petunia axillaris subsp. Axillaris (11); and (iii) Banana streak virus (BSV) in several interspecific banana hybrids obtained by crosses between Musa balbisiana (B genome) and Musa acuminata (A genome) (12,13). Mechanisms that lead to integration, activation, and subsequent episomal infection are complex and still largely unknown.…”

“…Indeed, the PVCV genome is integrated in tandem arrays in a complete, continuous form as a "retro provirus"; its activation resembles that of retroviruses and involves the production of a greater-than-full-length transcript that could be reverse transcribed into DNA (16,17). On the other hand, BSV Goldfinger species (BSGFV) is present in the diploid M. balbisiana (BB) Pisang klutuk wulung (PKW) plant as a diallelic integration much longer than a single viral genome, exhibiting a succession of partial viral sequences that are sometimes inverted and partially duplicated, representing at least one total viral genome (13). Based on the endogenous BSGFV sequence (eBSGFV), an activation process based on a direct transcription event seems unlikely to occur alone.…”