3.4 Genetic and phylogenetic analysis
The σC genes of both newly identified NDRV isolates were 1568 bp in
length. To further investigate the genetic characteristics of both newly
isolated NDRV strains, their σC genes and induced amino acid were
compared with reference WRV strains. According to the sequence alignment
of σC genes, Nucleotide identity between HNXX-1/2021 and HNJZ-2/2021 was
99.1%, which shared 98.4% and 98% identities with DRV/SY/Jiangsu/2018
in nucleotide, and 98.8% and 99.1% in deduced amino acid,
respectively. Meanwhile, HNXX-1/2021 and HNJZ-2/2021 shared 98.4% and
98% in nucleotide, 98.5% and 98.8% in deduced amino acid with
DRV/SDHZ17/Shangdong/2017, respectively. The nucleotide sequences of the
σC gene of HNXX-1/2021 and
HNJZ-2/2021 were deposited into GenBank (accession numbers: ON012751 and
ON012752).
To further explore the evolutionary characters of the newly identified
NDRV strains,
the
phylogenetic tree of NDRVs was constructed based on the σC genes deduced
amino acid sequences (Figure 3). As shown in the phylogenetic tree,
HNXX-1/2021 and HNJZ-2/2021 were clustered together with
DRV/QR/Hubei/2020, DRV/GX-Y7/Guangxi, DRV/SDLY18/Shandong/2018 and
DRV/SY/Jiangsu/2018, Which were NDRV strains emerged in recent years in
China.
Remarkably, all the DRVs strains were clustered into two distinct
clades. Clade1 comprised the majority of DRVs strains that emerged
before 2017, and few strains only emerged in Shandong province after
2017. Clade 2 comprised the majority of the NDRV strains that emerged
after 2017, including the newly identified NDRV strains HNXX-1/2021 and
HNJZ-2/2021 in this study.