Chloroplast genome structures and evolution analyses of two hemiparasitic species from genus Taxillus

• Published in: Genome Vol. 60; no. 11; p. 1017
• Main Authors: Zhou, Jianguo, Yao, Hui, Chen, Xinlian, Li, Ying, Song, Jingyuan, Chen, Shilin, Li, Yonghua, Cui, Yingxian
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing NRC Research Press 01.11.2017
• Subjects: Biological evolution; Chloroplasts; Evolution; Flowers & plants; Gene duplication; Gene sequencing; Genes; Genomes; Loranthaceae; Medicinal plants; Parasitic plants; Photosynthesis; Phylogeny; Pseudogenes; Species; Species classification; tRNA
• ISSN: 0831-2796; 1480-3321

Background: Chloroplast genomic information is valuable in investigating plant evolution, barcode-based identification, and phylogenetic relationships among different species. The chloroplast genome of parasitic plants has many variations. The parasitic plants of Loranthaceae are hemiparasites that retain photosynthesis. In this paper, we report the complete chloroplast genome of two medicinal plants, Taxillus chinensis and Taxillus sutchuenensis, which are the first two complete chloroplast genome sequences of Loranthaceae. Results: The complete chloroplast genome of T. chinensis, which was divided into a large single-copy region (LSC, 70 355 bp) and a small single-copy region (SSC, 6082 bp) and separated by a pair of inverted repeats (IRs, 22 462 bp each), was a circular 121 361 bp-long molecule. The complete chloroplast genome of T. sutchuenensis was 122 562 bp long and retained a typical structure with LSC (70 630 bp), SSC (6102 bp), and two IRs (each 22 915 bp long). The GC contents of both species were 37.3% each. A total of 106 genes was identified from each genome. Each genome consisted of 66 protein-coding genes, 28 tRNAs, 8 rRNAs, and 4 pseudogenes, including rpl16, rpl2, and ycf15 (duplicate gene). All ndh genes, three ribosomal protein genes (rpl32, rps15, rps16), seven tRNA genes (trnA-UGC, trnG-UCC, trnH-GUG, trnL-GAU, trnK-UUU, trnL-UAA, trnV-UAC), four ycf genes (ycf1, ycf5, ycf9, ycf10), and the infA gene of the two species were lost. Taxillus chinensis and T. sutchuenensis were associated with Schoepfia jasminodora (Olacaceae), whereas three species of genus Viscum were grouped with Osyris alba (Santalaceae) based on the phylogenetic tree. The phylogenetic results strongly supported the theory that Loranthaceae and Viscoideae are separate evolutionary groups. Significance: Our results demonstrated the effect of parasitic lifestyle on the chloroplast structure and genome content of T. chinensis and T. sutchuenensis. The chloroplast genome also significantly contributes to the classification and evolution of species of Taxillus.