Could you please exlain the figures and data? Examination of the fate of individ
ID: 256427 • Letter: C
Question
Could you please exlain the figures and data?
Examination of the fate of individual virus variants during transmission
to birds and subsequent acute infection (Figure 4A)
showed that five of seven synonymous consensus changes
(Figure 4B) and 50% of the total synonymous variants were
conserved (Figure 4C; which increased to 90% during peak
viremia). The two synonymous consensus changes lost were
accompanied by a nonsynonymous mutation. In contrast, only
about 10% of the nonsynonymous variants were conserved (Figure 4C), including only one of six nonsynonymous consensus
changes (Figure 4B). Moreover, an estimate of selection, dN/dS,
supports that purifying selection increased (i.e., smaller dN/dS ratios)
duringWNVinfection of birds (Figure 3D). Purifying selection
was the strongest in the structural protein coding region during
replication in birds but was not regionally different in mosquitoes
(Figure 4D). These results suggest that the WNV populations do
not encounter severe bottlenecks during transmission to birds
and that evolution is mainly determined by selection.
Figure 4. Relaxed Bottlenecks and Strong
Purifying Selection during Bird Infection
(A) Individual virus variants from combined replicates
per group were plotted by their frequency
and WNV genome position (yellow, structural protein
region; purple, non-structural protein region).
Red dots indicate synonymous mutations, and
black dots indicate nonsynonymous mutations.
(B) Virus consensus sequence changes (>0.5 frequency,
dotted line) detected in the mosquito
saliva were tracked during transmission to birds.
No new consensus changes arose during bird
infection.
(C) The proportion of variants (mean with 95%
CI) detected in subsequent populations (conservation)
were tracked from the mosquito bloodmeal
through transmission to birds.
(D) The strength of host selection on virus populations,
estimated by dN/dS (mean with 95% CI),
was tracked during transmission and bird infection.
dN/dS values < 1 (dotted line) represent strong
purifying selection.
Explanation / Answer
West Nile viruses (WNV) belong to genus flavivirus, arthropod borne or arbovirus, can be transmitted through mosquito and thus, may pose threats to maintaining public health. Initially, the infections caused by WNV was noticed to be mild and infectious to lesser degree. Mutations in the RNA of WNV, resulted in emergence of new variant of the viruses. Mutations also increased the pathogenesis of WNV in birds and their effectiveness in mosquitoes (Culex). Thus, the genetic diversity of the WNV are studied as dynamic changes, during the transmission cycle of the virus.
This can be experimented by sampling mosquito saliva and bird serum repeatedly or temporarily.
During subsequent analysis of the saliva, it is observed that the virus in saliva expectorate was different, diverse, and unique. However, when these variant viruses were transmitted to the bird, during each feeding incident, the inferred mutation may be lost. This result reflects, that though WNV can mutate rapidly in mosquito, rendering variant fitness. This fitness is lost (described as: fitness trades off), during each feeding episode, in vivo in birds, due to genetic drift, leading to slower evolutionary changes (evolution dynamics.
A. The mutations in the viral RNA were noted as:
a) synonymous- mutation that causes no change in amino acid and thus is not important in evolution.
b) non-synonymous- mutation that causes changes in amino acids and thus is important in evolution process.
In this case, there was only non-synonymous 10% change. This is indicated by the mutation occurring (synonymous or non-synonymous- mutation) in the structural proteins (yellow color bar) and non-structural proteins (purple color bar). The dots in red depict the synonymous- mutation, that had occurred. Black dots depict non-synonymous- mutation that occurred. It is seen, that not much changes occurred in amino acid due to mutation.
B. The consensus sequences are observed as amino acid sequence here. It depicts that, the mutation that occurred in the mosquito, (observed by the change in consensus sequences), were reverted to normal, when the virus entered in the bird (indicated by dots per inches).
C. The bars represent the conservation of the sequences. Total mutation is represented with gray, red represents synonymous- mutation, black represent non- synonymous- mutation. The size of the red bar, indicates that the synonymous- mutation were conserved in birds. During viremia, this increased. However, the subsequent effect of synonymous- mutation were reverted.
D. The genomic mutation that can survive during selection in the host, is indicated by genetic bottle neck. The evolutionary rate is measured by dN/dS ratio (average genetic distance) with 95% CI (confidence interval). Relaxed bottle necks indicate neutral effect of mutation. The graph dN/dS is higher ;level in saliva (for coding and structural gene) and lower in peak is observed, indicating no effect of mutation.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.