Unique Genetic Traits and Mixing in Virus Affecting Bitter Melon

Greg Howard
29th July, 2024

Unique Genetic Traits and Mixing in Virus Affecting Bitter Melon

Image Source: Natural Science News, 2024

Key Findings

  • The study, conducted by Tamil Nadu Agricultural University from 2019 to 2022, found that Tomato leaf curl New Delhi virus (ToLCNDV) infects bitter gourd in India with a high prevalence rate of 92.43%
  • ToLCNDV isolates in bitter gourd show only 88% DNA-A component identity with other ToLCNDV isolates, indicating significant genetic divergence
  • The study proposes that due to unique genomic features and less than 90% identity with other isolates, the ToLCNDV isolates should be classified as a distinct strain, named ToLCNDV-BG
Tomato leaf curl New Delhi virus (ToLCNDV) and bitter gourd yellow mosaic virus (BgYMV) are two begomoviruses that infect bitter gourd in India. Recent research conducted by Tamil Nadu Agricultural University has shed light on the predominance and unique characteristics of these viruses, particularly ToLCNDV, in the region[1]. This study, conducted from 2019 to 2022, found that ToLCNDV is significantly more prevalent, with an infection rate of 92.43%, compared to BgYMV's 44%. Begomoviruses, a family of plant viruses, cause significant agricultural damage worldwide. These viruses have single-stranded DNA genomes and express four to eight genes from both strands of their double-stranded DNA replicative intermediate[2]. The proteins encoded by these viruses facilitate various functions, including replication, movement, and counteracting plant defenses. Understanding the genetic diversity and evolutionary mechanisms of these viruses is crucial for developing effective control strategies. The study revealed that the ToLCNDV isolates infecting bitter gourd share only 88% identity in the DNA-A component with other ToLCNDV isolates, indicating they are a distinct variant. This low identity percentage suggests that these isolates have undergone significant genetic divergence. The predicted amino acid sequences of the viral proteins, including the replication initiation protein, coat protein, and symptom determinant protein, show marked differences from other geminiviruses. Notably, the RCR motif I and RCR motif III, crucial regions for replication, are different from those found in other geminiviruses. ToLCNDV's genetic diversity can be partially explained by the evolutionary pressures acting on its genes. Previous studies have shown that the C4(AC4) genes of geminiviruses, which are entirely overprinted on the C1(AC1) genes, are under positive selection, while the C1(AC1) sequences are under purifying selection[3]. This means that the C4(AC4) genes accumulate mutations that may confer advantageous traits, while the C1(AC1) genes remain relatively unchanged to maintain essential functions. This evolutionary mechanism could contribute to the genetic diversity observed in ToLCNDV isolates. The infectivity of cloned components of one of the ToLCNDV isolates, designated ToLCNDV-BG NP, was demonstrated in bitter gourd, confirming the virus's ability to infect this host. Recombination analysis revealed that the study isolates are recombinants, with the major parent predicted as squash leaf curl Yunnan virus and the minor parent as ToLCNDV from Pakistan. Recombination is a process where genetic material from different viral strains combines to form new variants, contributing to the genetic diversity and evolution of viruses. Due to the distinct genomic features and less than 90% identity with the majority of ToLCNDV isolates, the study isolates have been proposed to be raised to the status of a distinct strain, designated as ToLCNDV-BG. This finding is significant as it highlights the ongoing evolution and diversification of begomoviruses, which can complicate efforts to manage and control these plant pathogens. In summary, the study conducted by Tamil Nadu Agricultural University provides valuable insights into the genetic diversity and evolutionary mechanisms of ToLCNDV infecting bitter gourd in India. The identification of a distinct ToLCNDV variant with unique genomic features underscores the importance of continuous monitoring and research to understand the evolution of plant viruses and develop effective control strategies. This research builds on previous findings about the evolutionary pressures on geminivirus genes[3] and the multifunctional roles of viral proteins[2], contributing to our understanding of how these viruses adapt and diversify.

GeneticsBiochemPlant Science

References

Main Study

1) Genomic distinctiveness and recombination in tomato leaf curl New Delhi virus (ToLCNDV-BG) isolates infecting bitter gourd.

Published 29th July, 2024

https://doi.org/10.1007/s13205-024-04009-3

Related Studies

2) Geminivirus protein structure and function.

https://doi.org/10.1111/mpp.12032

3) Positive selection and intrinsic disorder are associated with multifunctional C4(AC4) proteins and geminivirus diversification.

https://doi.org/10.1038/s41598-021-90557-0


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