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Front. Plant Sci. | doi: 10.3389/fpls.2018.00359

Positive selection driving cytoplasmic genome evolution of the medicinally important ginseng plant genus Panax

 Peng Jiang1, Fengxue Shi2, Mingrui Li3,  Bao Liu1,  Jun Wen4, Hongxing Xiao1 and  Linfeng Li3*
  • 1Key Laboratory of Molecular Epigenetics of MOE, Northeast Normal University, China
  • 2Northeast Normal University Natural History Museum, China
  • 3Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, China
  • 4Department of Botany, Smithsonian National Museum of Natural Hisotry (SI), United States

Panax L. (the ginseng genus) is a shade-demanding group within the family Araliaceae and all of its species are of crucial significance in traditional Chinese medicine. Phylogenetic and biogeographic analyses demonstrated that two rounds of whole genome duplications accompanying with geographic and ecological isolations promoted the diversification of Panax species. However, contributions of the cytoplasmic genomes to the adaptive evolution of Panax species remained largely uninvestigated. In this study, we sequenced the chloroplast and mitochondrial genomes of 11 accessions belonging to seven Panax species. Our results show that heterogeneity in nucleotide substitution rate is abundant in both of the two cytoplasmic genomes, with the mitochondrial genome possessing more variants at the total level but the chloroplast showing higher sequence polymorphisms at the genic regions. Genome-wide scanning of positive selection identified five and 12 genes from the chloroplast and mitochondrial genomes, respectively. Functional analyses further revealed that these selected genes play important roles in plant development, cellular metabolism and adaptation. We therefore conclude that positive selection might be one of the potential evolutionary forces that shaped nucleotide variation pattern of these Panax species. In particular, the mitochondrial genes evolved under stronger selective pressure compared to the chloroplast genes.

Keywords: Araliaceae, Cytoplasmic genome, Genome sequencing, Panax, positive selection

Received: 07 Jan 2018; Accepted: 05 Mar 2018.

Edited by:

Renchao Zhou, Sun Yat-sen University, China

Reviewed by:

Yang Liu, Fairy Lake Botanical Garden (CAS), China
Nian Wang, Shandong Agricultural University, China
Hui-Run Huang, South China Botanical Garden (CAS), China  

Copyright: © 2018 Jiang, Shi, Li, Liu, Wen, Xiao and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Linfeng Li, Fudan University, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Shanghai, 200438, China,