title: Novel Insights on Hantavirus Evolution: The Dichotomy in Evolutionary Pressures Acting on Different Hantavirus Segments.
abstract: BACKGROUND
  Hantaviruses are important emerging zoonotic pathogens. The current understanding of hantavirus evolution is complicated by the lack of consensus on co-divergence of hantaviruses with their animal hosts. In addition, hantaviruses have long-term associations with their reservoir hosts. Analyzing the relative abundance of dinucleotides may shed new light on hantavirus evolution. We studied the relative abundance of dinucleotides and the evolutionary pressures shaping different hantavirus segments.
  
  
  METHODS
  A total of 118 sequences were analyzed; this includes 51 sequences of the S segment, 43 sequences of the M segment and 23 sequences of the L segment. The relative abundance of dinucleotides, effective codon number (ENC), codon usage biases were analyzed. Standard methods were used to investigate the relative roles of mutational pressure and translational selection on the three hantavirus segments.
  
  
  RESULTS
  All three segments of hantaviruses are CpG depleted. Mutational pressure is the predominant evolutionary force leading to CpG depletion among hantaviruses. Interestingly, the S segment of hantaviruses is GpU depleted and in contrast to CpG depletion, the depletion of GpU dinucleotides from the S segment is driven by translational selection. Our findings also suggest that mutational pressure is the primary evolutionary pressure acting on the S and the M segments of hantaviruses. While translational selection plays a key role in shaping the evolution of the L segment. Our findings highlight how different evolutionary pressures may contribute disproportionally to the evolution of the three hantavirus segments. These findings provide new insights on the current understanding of hantavirus evolution.
  
  
  CONCLUSIONS
  There is a dichotomy among evolutionary pressures shaping a) the relative abundance of different dinucleotides in hantavirus genomes b) the evolution of the three hantavirus segments.
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Sathish
authors.initials: S
authors.lastname: Sankar
authors.affiliation: Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, 110 016, India.
authors.forename: Mohita
authors.initials: M
authors.lastname: Upadhyay
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Mageshbabu
authors.initials: M
authors.lastname: Ramamurthy
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Kumaran
authors.initials: K
authors.lastname: Vadivel
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Kalaiselvan
authors.initials: K
authors.lastname: Sagadevan
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Balaji
authors.initials: B
authors.lastname: Nandagopal
authors.affiliation: Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, 110 016, India.
authors.forename: Perumal
authors.initials: P
authors.lastname: Vivekanandan
authors.affiliation: Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, Vellore, 632 055, Tamil Nadu, India.
authors.forename: Gopalan
authors.initials: G
authors.lastname: Sridharan
mesh_terms: D005075:Biological Evolution; D003141:Communicable Diseases / Q000235:genetics; D018899:CpG Islands; D006476:Orthohantavirus / Q000235:genetics*; D009154:Mutation; D010802:Phylogeny