Dynamics of Genetic Diversity Among Indian Sugarcane Bacilliform Virus Species and Implications of Associated Recombination Events in the Virus

Sugarcane bacilliform virus (SCBV), a plant pararetrovirus causing leaf fleck disease in sugarcane across the globe. Since the virus occurs throughout the sugarcane growing areas and germplasm in India, we have assessed the genetic divergences among the virus isolates from 104 isolates infecting germplasm and Saccharum hybrid varieties. With the evidence gathered from phylogenetic analysis and sequence demarcation tool, five novel genotypes are being proposed: SCBV-U, SCBV-V, SCBV-W, SCBV-X and SCBV-Y. SCBV-W: CBJ 46, due to the divergence in the nucleotide and protein sequence with existing isolates, established itself as a novel candidate in SCBV species. In comparison with the existing database of SCBV and conclusion from the present study, SCBV isolates from India exhibited maximum diversity in comparison with other regions. SCBV-U, SCBV-W, SCBV-X which turned out as potent recombinants along with other six recombinants in the study, directs at the plausible heterogeneity and genetic exchange happened within SCBV species over time which lead to the evolution of new variants. Neutrality tests indicate the existence of low-frequency polymorphism and Selection pressure of < 1 pointed out at purifying selection. Codon usage bias acted as an efficient tool for identifying patterns in SCBV, in which non-randomness in mutational events might lead to the over expression of codon AGA. The current study on characterization and evidence of nucleotidal variation within SCBV species will lead to devising robust diagnostics of the virus in quarantine and improving the knowledge on the evolutionary changes in SCBV species.

Dynamics of genetic diversity among Indian Sugarcane bacilliform virus species and implications of associated recombination events in the virus

Sugarcane bacilliform virus (SCBV), a plant pararetrovirus causing leaf fleck disease in sugarcane across the globe. Since the virus occurs throughout the sugarcane growing areas and germplasm in India, we have assessed the genetic divergences among the virus isolates from 104 isolates infecting germplasm and Saccharum hybrid varieties. With the evidence gathered from phylogenetic analysis and sequence demarcation tool, five novel genotypes are being proposed: SCBV-U, SCBV-V, SCBV-W, SCBV-X and SCBV-Y. SCBV-W: CBJ 46, due to the divergence in the nucleotide and protein sequence with existing isolates, established itself as a novel candidate in SCBV species. In comparison with the existing database of SCBV and conclusion from the present study, SCBV isolates from India exhibited maximum diversity in comparison with other regions. SCBV-U, SCBV-W, SCBV-X which turned out as potent recombinants along with other six recombinants in the study, directs at the plausible heterogeneity and genetic exchange happened within SCBV species over time which lead to the evolution of new variants. Neutrality tests indicate the existence of low-frequency polymorphism and Selection pressure of < 1 pointed out at purifying selection. Codon usage bias acted as an efficient tool for identifying patterns in SCBV, in which non-randomness in mutational events might lead to the over expression of codon AGA. The current study on characterization and evidence of nucleotidal variation within SCBV species will lead to devising robust diagnostics of the virus in quarantine and improving the knowledge on the evolutionary changes in SCBV species.

An Algorithmic framework for genome-wide identification of Sugarcane (Saccharum officinarum L.)-encoded microRNA targets against SCBV

Sugarcane Bacilliform Virus (SCBV) is considered an economically the most damaging pathogen for sugarcane production worldwide. Three ORFs are characterized in a single molecule of circular, ds-DNA genome of the SCBV, encoding for hypothetical protein (ORF1), DNA binding protein (ORF2) and Polyprotein (ORF3). The study was aimed to predict and comprehensively evaluate sugarcane miRNAs for the silencing of SCBV genome using in-silico algorithms. Computational methods were used for prediction of candidate miRNAs from sugarcane (S. officinarum L.) to silence the expression of SCBV genes through translational inhibition by mRNA cleavage. Mature sugarcane miRNAs were retrieved and were assessed to hybridization with the SCBV genome. A total of fourteen potential candidate miRNAs from sugarcane were computed by all the algorithms used for the silencing of SCBV. A consensus of three algorithms predicts hybridization sites of sof-miR159e at common locus 5534. The miRNA-mRNA interaction was estimated by computing free-energy of miRNA-mRNA duplex using RNAcofold algorithm. Regulatory network of predicted candidate miRNAs of sugarcane with SCBV ORFs, generated using Circos, identify novel targets. Consequently, detecting and discarding inefficient amiRNAs prior to cloning would help suppressed mutants faster. The efficacy of predicted candidate miRNAs was evaluated to test the survival rate of the in vitro amiRNA-mediated effective badnaviral silencing and resistance in sugarcane cultivars.