Quantitation of Multipartite Banana Bunchy Top Virus Genomic Components and Their Transcripts in Infected Tissues of Banana (Musa acuminata)

Abstract

Banana bunchy top disease (BBTD), caused by a Banana Bunchy Top Virus (BBTV), is the most devastating viral disease of bananas. The genome of multipartite BBTV is about 1 Kb in size and comprises six circular single-stranded (ss) DNA components, namely DNA-R, C, S, M, U3, and N. Gene expression in multipartite DNA viruses is highly flexible due to variations in the copy number and transcript levels of individual genomic components. This enables them to adapt to changing conditions and maintain optimal fitness. In the current study, the copy number of each genetic component of BBTV and its transcript level were determined in the leaf, midrib, and root tissue of the infected banana plant. The results of the study showed that DNA copies (copies/ng) were higher in midrib (11,105 ± 10,704.42), followed by leaf (6902.91 ± 1651.14), and were lowest in root (23.49 ± 9.21) tissues. In contrast, the transcript level was highest in the root (312.45 ± 106.69) and lowest in the midrib (0.72 ± 0.16). This suggests that BBTV independently regulates the transcriptional level of each DNA component. The distribution of BBTV in different tissues assists the identification of significantly higher viral load tissues for early and sensitive disease diagnosis, which will be beneficial for better disease management.

Effect of Banana bunchy top virus on the life cycle and fecundity of its insect vector

“…DNA amplification was performed using BBTV-specific primers that recognize part of the DNA-C genome, namely C-F (5'- GAATCGTCTGCTATGCCTG-3') and C-R (5'-CCAGAACTCCATTTCTCTTC-3') with a target DNA of approximately ±1018 pb. [17]. Amplification was carried out with a pre-denaturation stage for 5 min at 94 °C, followed by 35 cycles consisting of denaturation for 1 min at 94 °C, annealing for 35 sec at 50 °C, elongation for 90 sec at 72 °C, and post-elongation for 7 min at 72 °C.…”

The genome formula of a multipartite virus is regulated both at the individual segment and the segment group levels

“…This was first formalized for the multipartite single-stranded DNA (ssDNA) faba bean necrotic stunt virus (FBNSV), where some segments accumulate a lot while others are relatively rare [1]. Subsequently, the differential accumulation of genome segments in the host has been characterized for other multipartite DNA [2][3][4][5][6] and RNA [7] viruses and for segmented RNA viruses [8,9]. Because it was found in viruses with different genome nature and organization and infecting plants or animals, the differential accumulation of segments seems to be a common feature of viruses with fragmented genomes.…”