3.4 Analysis of nucleotide sequence in the rep and amino
acid sequence of the rep protein
The rep genes of 68 PiCV strains of the 120 PiCV positive samples
were successfully sequenced. Detailed information on the 68 PiCV strains
is shown in Table 2 and S1. The rep gene of 68 samples obtained
in this study were used to compare with PiCV reference sequences from
China and other countries. The results showed that the rep gene
of all 68 strains had been detected as two sizes: 948 nt and 954 nt.
Forty of the 68 rep nucleotide sequences were 948 nt in length,
encoding a rep protein of 315 amino acid residues. Twenty-eight
of the 68 rep nucleotide sequences were 954 nt in size, encoding
a rep protein of 317 amino acid residues (Table 2 and S1). The
sequence comparison of the rep genes revealed nucleotide
homologies of 90.3%–100% and deduced amino acid homologies of
92.7%–100% among the 68 PiCV strains. The rep genes of the 68
identified PiCV strains exhibited high sequence similarities with
Chinese PiCV reference strains (89.0%–99.2% nucleotide identity,
89.2%–99.6% amino acid identity) and the PiCV reference strains from
the other countries (89.5%–98.3% nucleotide identity, 90.5%–99.3%
amino acid identity) (Table 3). To investigate variations in the deduced
amino acid sequences of rep gene products, the amino acid
sequences of 68 PiCV strains including the reference strains were
aligned. The results showed that some unique amino acid substitutions at
37 different positions were observed among the 68 identified PiCV
strains as shown in Table 5.