Comparative Complete Chloroplast Genome of Nine Species in Litsea (Lauraceae) and Uncover Evolutionary Dynamic Patterns

Background: Litsea , Lauraceae, is a group of evergreen trees or shrubs that widely distributed in tropical and subtropical countries, such as Asia and America. Species in Litsea are spontaneously distributed at a maximum altitude of 2,700 m from sea level. Pants and its extractions from Litsea species cover a wide range of medicinal and industrial values. The aromatic oil extracted from Litsea is of great value with citral as its main component. At present, studies related to gene resources of Litsea are limited in the morphological analysis, while studies at the genetic level are insufficient. We therefore firstly assembled and annotated the complete chloroplast genome of nine species in Litsea, carried out a serious of comparative analysis, and completed the construction of phylogenetic tree within genus Litsea. Results: The genome length ranged from 152,051 to 152,717 bp. A total of 128 genes were identified, including 84 protein-coding genes, 36 rRNA genes and 8 tRNA genes. High consistency of codon bias, repeats, divergent analysis, single nucleotide polymorphisms (SNP) and insertions and deletions (InDels) revealed highly conserved chloroplast phenotypes in species within the genus Litsea . Changes in gene length and the present of pseudogene ycf1 Ψ that caused by IR contraction and expansion were reported. The non-coding regions, especially atpF - atpH and ndhC - trnV-UAC presented high gene divergence. PsbJ - psbE regions showed remarkably high nucleotide diversity (Pi) values. Furthermore, we constructed two phylogenetic trees, demonstrating two dominant clades within genus Litsea . And the differences between trees constructed by full chloroplast (cp) genome and protein-coding genes were revealed. Conclusion: Overall, the evolutionary pattern of Litsea species regarding structural features, repeats sequences and variations presented high consistency. Valuable genomic resources and theoretical basis were also provided for further research of taxonomic discrepancies, molecular marker-assisted breeding and phylogenetic relationships of Litsea and other angiosperm species.