New Mitovirus Discovered in Passion Fruit, Expanding Understanding of Plant-Associated Viruses.
Mitoviruses, a unique group of viruses without capsids, are part of the Mitoviridae family and are known to replicate exclusively within the mitochondria of fungi. However, recent findings have revealed that these viruses might have a broader host range than previously believed. Complete mitovirus-like sequences have been identified in plant transcriptome data and leaf tissue samples, suggesting that plants, too, might be susceptible hosts.
In a groundbreaking study, researchers from the Universidade Federal de Campina Grande have discovered a new mitovirus associated with passion fruit (Passiflora spp.), a vital crop in tropical and subtropical regions. The presence of this virus is particularly noteworthy because viral diseases are a significant threat to passion fruit production. Understanding these viral agents is crucial for developing effective management strategies to protect the crop.
During a large-scale genomic study aimed at identifying viruses that infect Passiflora spp. in Brazil, the researchers detected a de novo-assembled contig. This contig, approximately 2.6 kilobases in length, showed significant similarity to other plant-associated mitoviruses. The researchers named this virus “passion fruit mitovirus-like 1” (PfMv1). The contig contains a single open reading frame (ORF) that encodes RNA-dependent RNA polymerase (RdRP), an enzyme essential for RNA virus replication.
Further analysis revealed that the predicted amino acid sequence of PfMv1’s RdRP shared six conserved motifs with other plant-associated mitoviruses. This finding aligns with previous studies that identified similar motifs in other mitoviruses, such as walking iris virus 1 (WIV1) and Paris mitovirus 1 (ParMV1). PfMv1 exhibited 79% coverage and 50.14% identity to Humulus lupulus mitovirus 1, indicating a close relationship with other plant-associated mitoviruses.
Phylogenetic analysis confirmed that PfMv1 belongs to the genus Duamitovirus, clustering with other plant-associated mitoviruses. This classification is consistent with earlier phylogenetic studies that have categorized mitoviruses into distinct genera based on their RdRP sequences. The researchers further validated the presence of PfMv1 in passion fruit samples using reverse transcription polymerase chain reaction (RT-PCR). Importantly, they did not find any corresponding DNA, which rules out the possibility that this sequence is an integrated viral-like sequence within the host genome.
This study marks the first identification of a replicating mitovirus associated with Passiflora edulis. The researchers propose naming it “Duamitovirus passiflorae.” This discovery adds to the growing knowledge of plant-associated mitoviruses and highlights the diversity of these viruses across different plant species.
Mitoviruses have been previously identified in various hosts, including both fungi and plants. For instance, Rhizoctonia oryzae-sativae mitovirus 1 (RoMV1) was the first mitovirus genome sequence reported in the phytopathogenic fungus R. oryzae-sativae. Similarly, WIV1 was the first putative mitovirus identified in a monocotyledonous plant. The discovery of PfMv1 in passion fruit broadens the known host range of mitoviruses and emphasizes the need for ongoing surveillance and genomic studies to uncover the full extent of viral diversity in plants.
As more viral genome sequences are determined, there is a growing demand for computational tools to assist in their classification. The Sequence Demarcation Tool (SDT) is one such tool, providing a reliable and reproducible method for classifying nucleotide or amino acid sequences based on pairwise genetic identity. This tool can generate publication-quality pairwise identity plots and color-coded distance matrices, aiding researchers in classifying new viral sequences according to International Committee on Taxonomy of Viruses (ICTV) criteria.
In conclusion, the discovery of PfMv1 in passion fruit by researchers at the Universidade Federal de Campina Grande represents a significant advancement in our understanding of plant-associated mitoviruses. This finding not only expands the known diversity of mitoviruses but also underscores the importance of genomic studies in identifying and characterizing new viral agents that could impact economically important crops.