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Comparative study on genomes of two Japanese melon necrotic spot virus isolates
K Ohshima1, T Ando, N Motomura
1Laboratory of Plant Virology, Faculty of Agriculture, Saga University, 1-banchi, Honjo-machi, Saga 840-8502, Japan. ohshimak@cc.saga-u.ac.jp
Abstract:
Nucleotide sequences of the genomes of two Japanese Melon necrotic spot virus (MNSV) isolates, NH and NK were determined. The open reading frames (ORFs) in both genomes encode five proteins: p29 (the pre-readthrough domain of p89), p89 (the readthrough domain of p89 identified as the putative RNA-dependent RNA polymerase), p14 (the pre-readthrough domain of p7A), p7A (the putative movement protein), and p42 (coat protein, CP). Nucleotide and amino acid sequence identities of the five proteins of NH and NK isolates were estimated at 97.4-99.5% and 97.7-100%, respectively. NK isolate but not NH isolate infected systemically leaves of Cucumis melo plants. When deduced amino acid sequences of p7A proteins of NH and NK isolates were compared, only one difference at position 16 (serine in NH isolate and isoleucine in NK isolate) was observed. p7A protein is considered the putative movement protein. The serine of p7A protein of NH isolates may be involved in systemic infection. In addition, phylogenetic relationships of genes based on nucleotide sequences revealed that NH and NK isolates might form a group, and S isolate, serologically different from NH and NK isolates, might represent a distinct isolate not belonging to this group.
Insights
Two Japanese Melon necrotic spot virus (MNSV) isolates, NH and NK, were sequenced. A single amino acid difference in the movement protein (p7A) may explain the NK isolate's systemic infection capability in melon plants.
Area of Science:
- Plant Virology
- Molecular Biology
- Genomics
Background:
- Melon necrotic spot virus (MNSV) causes significant crop losses globally.
- Understanding genetic diversity and virulence factors of MNSV isolates is crucial for disease management.
Purpose of the Study:
- To determine the complete nucleotide sequences of two Japanese MNSV isolates (NH and NK).
- To compare the genetic and protein sequences of these isolates.
- To investigate potential molecular determinants of systemic infection.
Main Methods:
- Whole-genome sequencing of MNSV NH and NK isolates.
- Open reading frame (ORF) analysis to identify encoded proteins.
- Sequence identity comparisons at nucleotide and amino acid levels.
- Phylogenetic analysis based on nucleotide sequences.
Main Results:
- Genomes of NH and NK isolates encode five proteins: p29, p89 (RNA-dependent RNA polymerase), p14, p7A (movement protein), and p42 (coat protein).
- High nucleotide (97.4-99.5%) and amino acid (97.7-100%) sequence identities were observed between NH and NK isolates.
- Only the NK isolate caused systemic infection in Cucumis melo plants.
- A single amino acid difference (Serine vs. Isoleucine at position 16) in the p7A movement protein was identified between the isolates.
- Phylogenetic analysis suggested NH and NK form a distinct group, separate from the MNSV S isolate.
Conclusions:
- The p7A movement protein sequence variation, specifically the serine at position 16 in the NH isolate, may influence systemic infection capability.
- The genetic distinctness of the MNSV S isolate warrants further investigation.
- Comparative genomics provides insights into MNSV evolution and pathogenicity.