The complete chloroplast genome and phylogenetic analysis of Oxytropis kansuensis Bunge (Fabaceae)

Abstract

Oxytropis kansuensis Bunge holds significant medicinal and ecological values. Nevertheless, the absence of a complete chloroplast genome has impeded our ability to better understand and utilize this plant. In this study, the complete chloroplast genome of O. kansuensis was sequenced and de novo assembled for the first time. The total genome length was determined to be 127,115 bp, with a guanine-cytosine (GC) content of 34.29%. It was observed that the inverted repeat (IR) region was absent in this species. A total of 110 genes were annotated, including 76 PCGs, 30 tRNA genes, and four rRNA genes. A phylogenetic tree was constructed from the complete chloroplast genome sequences of 10 Oxytropis species and seven Astragalus species. The result indicated that Oxytropis and Astragalus clearly form distinct monophyletic lineages, respectively, and O. kansuensis is most closely related to the O. ochrocephala. This research not only enriches the genomic database but also establishes a firm foundation for future studies on O. kansuensis. Furthermore, it offers compelling scientific evidence to advance broader phylogenetic and evolutionary investigations of Oxytropis.

Keywords: Fabaceae; Oxytropis kansuensis; complete chloroplast genome; phylogenetic analysis.

Figure 1.

O. kansuensis (photographed by Dan Lei at Baima Mountain, Yunnan Province, China). (A) Habit; (B) habitat ; (C) individual (show a complete leaf sequence), (D) detail: a, standard; b and c, wings; d, keel; e, pistils; f, stamen; g, adaxial leaflet surface; h, abaxial leaflet surface; i, calyx (unfold); j, bracts (unfold); k and l, legumes; m, root nodule.

Figure 2.

Phylogenetic tree of species of the genera Oxytropis and Astragalus based on complete chloroplast genome sequences. Lotus japonicus is the outgroup, and O. kansuensis is shown in red, with nodes labeled with ML bootstrap support values (BS) and Bayesian posterior probabilities (PPs), separated by slashes. The species sequence is as follows: O. kansuensis (PQ790176.1), O. bicolor (NC_047482.1) (Su et al. 2019), O. ramosissima (PP868418.1), O. diversifolia (NC_062618.1), O. glabra (NC_056975.1) (Liu et al. 2021), O. aciphylla (OK143433.1), O. splendens (NC_050860.1), O. arctobia (MT409175.1), O. falcata (NC_083920.1), O. ochrocephala (OR897029.1) (Hu et al. 2024), A. laxmannii (NC_052923.1), A. lithophilus (NC_077544.1), A. membranaceus (KX255662.1) (Wang et al. 2016), A. mongholicus (KU666554.1) (Lei et al. 2016), A. tumbatsica (NC_083912.1), A. muliensis (NC_083909.1), A. oxyglottis (NC_077543.1), and L. japonicus (NC_002694.1) (Kato et al. 2000).

Figure 3.

Gene map of the cp genome of O. kansuensis. Genes plotted inside the circles are transcribed clockwise and genes plotted outside the circles are transcribed counterclockwise. The inner dark grey circle corresponds to GC content and the inner light grey circle corresponds to AT content. Different colors represent different genes in different functional groups.