Comparative and phylogenetic analysis of the complete chloroplast genome sequences of Lactuca raddeana and Lactuca sativa

Lactuca raddeana is a biennial plant of the Lactuca genus belonging to the Asteraceae family. The classification of Lactuca is controversial, and no consistent conclusions have been reached based on the analysis of morphological characters and different molecular markers. Here, we sequenced and assembled the complete chloroplast genome of L. raddeana. This genome has a total length of 152,339 bp, a conservative quartile structure that is composed of a large single-copy (LSC) region of 83,976 bp, a small-copy (SSC) region of 18,521 bp, and a pair of inverted repeats (IRs) of 24,921 bp. The genome contains 112 unique genes, including 79 protein-coding, four rRNA, and 29 tRNA genes. Repeat analysis obtained 17 microsatellite, 16 tandem, and 17 interspersed repeats. Comparison of sequence divergence between L. raddeana and L. sativa found the intergenic spacer trnC-petN exhibited the highest degree of variation. Three phylogenetic trees based on the 72 shared protein, matK gene, and rbcL gene sequences showed that L. raddeana and L. sativa are clustered together. The acquisition and comparative analysis of the chloroplast genome provide a valuable resource for the taxonomic and phylogenetic studies of Lactuca.