Expression profiling of microRNAs associated with virus infection in banana cultivar red banana (Musa AAA)

Abstract

The study entitled “Expression profiling of microRNAs associated with virus infection in banana cultivar Red Banana (Musa AAA)” was conducted at the Department of Plant Biotechnology, College of Agriculture, Vellayani, Thiruvananthapuram during 2018-2020. The objective was to study the expression of selected miRNAs in Banana bract mosaic virus (BBrMV) and Banana bunchy top virus (BBTV) infection in banana cultivar Red Banana (Musa AAA). In a study conducted in the Department of Plant Biotechnology, 52 mature miRNAs were predicted using NovoMIR software and over 142 targets were identified for these miRNAs using psRNATarget in the banana genome. On validation of these miRNAs, Subramanian (2019) found differential expression of a few of them in tissue culture grown banana var. Nendran infected with BBrMV. In this study, two of those miRNAs and their target genes i.e. miR-6928-5p (target: Flavin adenine dinucleotide dependent oxidoreductase gene) and miR-971-5p (target: Argonaute protein) were studied for their expression in field infected samples. Banana plants of cultivar red banana infected with BBrMV and BBTV were collected from the Instructional Farm, College of Agriculture, Vellayani, based on the visual symptoms. The BBrMV and BBTV infections were reconfirmed by PCR using the primers specific to coat protein genes of the viruses. All the infected samples showed the presence of specific amplicons of the expected size (745bp) compared to the uninfected samples. RNA isolated from the leaf samples of both control and infected plants were reverse transcribed to cDNA. The PCR analysis confirmed the presence of both miRNAs and their target genes in the banana samples. The expression analysis conducted by RT-qPCR showed differential expression of miR-6928-5p and miR-971-5p in BBrMV and BBTV infected plants. In BBrMV infected samples, miR-6928-5p was downregulated up to 0.01 fold and the BBTV infected samples showed an upregulation of this miRNA up to11.08 fold. The mRNA transcript encoding FAD dependent oxidoreductase showed downregulation in BBrMV infected samples (upto 0.43 fold) and in BBTV infected samples the change was marginal. But within the infected plants both miRNA and its target showed an inverse correlation. miR-971-5p was found to be down regulated in both BBrMV and BBTV infected samples (a maximum of 0.21 and 0.17 fold respectively). On the other hand, its target mRNA transcript encoding Argonaute protein showed a maximum of 3.09 and 1.89 fold increase in the BBrMV and BBTV infected samples. Here both miR-971-5p and its target gene showed an inverse correlation in their expression in both BBrMV and BBTV infection. The study showed that both miR-6928-5p and miR-971-5p respond to BBTV and BBrMV infection in banana cultivar red banana (Musa AAA).