Understanding the Genetic Makeup of a New Virus Affecting Birch Trees

Jim Crocker
9th June, 2024

Understanding the Genetic Makeup of a New Virus Affecting Birch Trees

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at the University of Idaho discovered a new virus, BTLV, in European white birch plants
  • BTLV has a unique genetic makeup, with two overlapping genes that produce essential viral proteins
  • The virus uses a special mechanism called frameshifting to produce multiple proteins from a single gene sequence
Researchers at the University of Idaho have discovered a novel virus named "birch toti-like virus" (BTLV) in European white birch (Betula pendula) plants[1]. This new virus belongs to the Totivirus genus, a group of double-stranded RNA viruses known to infect both fungi and plants. The genome of BTLV is 4,967 nucleotides long and encodes two overlapping open reading frames (ORFs) for the capsid protein (CP) and an RNA-dependent RNA polymerase (RdRP). The discovery of BTLV is significant due to its unique genetic makeup and its potential implications for understanding viral evolution and plant-virus interactions. The CP and RdRP proteins of BTLV share 46.9% and 60.2% amino acid sequence identity, respectively, with those of Panax notoginseng virus B. This indicates that while BTLV is related to other known totiviruses, it is distinct enough to be considered a new member of the genus. One of the key features of BTLV is the presence of a putative slippery heptamer signal 82 nucleotides upstream of the stop codon of ORF1. This signal suggests that a -1 translational frameshifting strategy is involved in the expression of ORF2. Frameshifting is a mechanism used by some viruses to produce multiple proteins from a single mRNA strand. It allows the ribosome to shift one nucleotide backward on the mRNA, thus changing the reading frame and producing a different protein. This mechanism has been observed in other totiviruses as well[2]. A study on frameshift sites in viruses identified a strong bias toward the two nucleotides 5' of the shifty heptamer signal, suggesting that an extended signal is involved in eukaryotic frameshifting[2]. Phylogenetic analysis based on the CP and RdRP amino acid sequences places BTLV within a clade of plant-associated totiviruses, with taro-associated virus as its closest relative. This analysis helps in understanding the evolutionary relationships between different totiviruses and can provide insights into how these viruses have adapted to infect different hosts. The discovery of BTLV expands our knowledge of the diversity within the Totivirus genus and highlights the potential for discovering new viruses in different plant species. Earlier studies have shown that totiviruses can have significant genomic variations even within the same species. For instance, the complete genomic sequence of a maize-associated totivirus variant from Ecuador (MATV-Ec) was found to be considerably longer than that of its Chinese counterpart (MATV-Ch), primarily due to a 1-kb-long capsid-protein-encoding fragment absent in the Chinese genome[3]. This kind of genomic variation underscores the complexity and adaptability of totiviruses, which can have different impacts on their host plants. The discovery of BTLV also raises questions about its potential impact on European white birch plants. While the study did not specifically address the pathogenicity of BTLV, understanding its genetic makeup and evolutionary relationships can help in predicting its behavior and interactions with its host. Further research will be needed to determine whether BTLV has any detrimental effects on birch trees or if it exists as a benign or symbiotic entity. In conclusion, the identification of birch toti-like virus by researchers at the University of Idaho adds a new member to the Totivirus genus and provides valuable insights into the genetic diversity and evolutionary history of plant-associated totiviruses. This discovery, along with previous findings on totivirus genomic variations and frameshifting mechanisms, enhances our understanding of viral evolution and plant-virus interactions, paving the way for future research in this field.

BiotechGeneticsPlant Science

References

Main Study

1) Molecular characterization of birch toti-like virus, a plant-associated member of the new family Orthototiviridae.

Published 8th June, 2024

https://doi.org/10.1007/s00705-024-06067-7

Related Studies

2) An extended signal involved in eukaryotic -1 frameshifting operates through modification of the E site tRNA.

Journal: Molecular cell, Issue: Vol 17, Issue 1, Jan 2005

3) Complete genome sequence of a variant of maize-associated totivirus from Ecuador.

https://doi.org/10.1007/s00705-016-3159-2


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