Analysis of codon usage bias in mitochondrial genome of Fopius arisanus(Sonan)
To provide a theoretical foundation for understanding the characteristics and evolutionary direction of the mitochondrial genome of Fopius arisanus(Sonan),this study investigated the codon use bias of this para-sitoid's entire mitochondrial genome and analyzed the factors influencing this bias.Thirteen protein-coding genes(PCGs)were studied by analyzing the GC content of three codon sites,effective number of codon(ENC)using CodonW and CAIcal,and relative synonymous codon usage(RSCU)using MEGA 11.The cause of codon usage bias was analyzed by neutrality plots and ENC-plot mapping.Results showed that the average GC con-tent of positions 1,2 and 3 among the 13 protein gene sequences was 20.65%,22.42%,and 6.42%,respec-tively.The overall average GC content was 16.50%.It revealed that the AU content of the protein coding se-quence was significantly higher than the GC content,and that the codons A/U were favoured by the mitochon-drial genome of F.arisanus at position 3.Thirteen optimal codons including UUU,UUA,AUU,GUA,UCU,AGA,CCA,ACU,GCU,GCA,AAA,CGA and GGA were screened based on their high frequency and expres-sion levels.The third site of these optimal codons preferred to use A/U.The average value of ENC was 29.50,and the neutral plot analysis showed that the correlation between the content of codon GC12 and GC3 was not sig-nificant(P=0.665).The results from the neutrality plots and ENC-plot both showed that natural selection was major influencing factor on codon usage bias in the mitochondrial genome of F.arisanus.