The complete chloroplast genome sequence of and , and comparative analysis within genus L.

Trees in the Morus genera belong to the Moraceae family. To better understand the species status of genus and to provide information for studies on evolutionary biology within the genus, the complete chloroplast (cp) genomes of and were sequenced. The plastomes of the two species are 159,265 bp and 159,103 bp, respectively, with corresponding 83 and 82 simple sequence repeats (SSRs). Similar to the SSRs of and cp genomes, more than 70% are mononucleotides, ten are in coding regions, and one exhibits nucleotide content polymorphism. Results for codon usage and relative synonymous codon usage show a strong bias towards NNA and NNT codons in the two cp genomes. Analysis of a plot of the effective number of codons (ENc) for five spp. cp genomes showed that most genes follow the standard curve, but several genes have ENc values below the expected curve. The results indicate that both natural selection and mutational bias have contributed to the codon bias. Ten highly variable regions were identified among the five spp. cp genomes, and 154 single-nucleotide polymorphism mutation events were accurately located in the gene coding region.