Complete chloroplast genome comparisons for Pityopsis (Asteraceae)

PLoS One. 2020 Dec 28;15(12):e0241391. doi: 10.1371/journal.pone.0241391. eCollection 2020.

Abstract

Pityopsis includes several regionally and one federally endangered species of herbaceous perennials. Four species are highly localized, including the federally endangered P. ruthii. The genus includes several ploidy levels and interesting ecological traits such as drought tolerance and fire-dependent flowering. Results from previous cladistic analyses of morphology and from initial DNA sequence studies did not agree with one another or with the infrageneric taxonomic classification, with the result that infrageneric relationships remain unresolved. We sequenced, assembled, and compared the chloroplast (cp) genomes of 12 species or varieties of Pityopsis to better understand generic evolution. A reference cp genome 152,569 bp in length was assembled de novo from P. falcata. Reads from other sampled species were then aligned to the P. falcata reference and individual chloroplast genomes were assembled for each, with manual gapfilling and polishing. After removing the duplicated second inverted region, a multiple sequence alignment of the cp genomes was used to construct a maximum likelihood (ML) phylogeny for the twelve cp genomes. Additionally, we constructed a ML phylogeny from the nuclear ribosomal repeat region after mapping reads to the Helianthus annuus region. The chloroplast phylogeny supported two clades. Previously proposed clades and taxonomic sections within the genus were largely unsupported by both nuclear and chloroplast phylogenies. Our results provide tools for exploring hybridity and examining the physiological and genetic basis for drought tolerance and fire-dependent flowering. This study will inform breeding and conservation practices, and general knowledge of evolutionary history, hybridization, and speciation within Pityopsis.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Asteraceae / classification
  • Asteraceae / genetics*
  • Chromosome Mapping
  • Genome, Chloroplast*
  • Molecular Sequence Annotation
  • Phylogeny
  • Southeastern United States
  • Species Specificity
  • Whole Genome Sequencing

Associated data

  • figshare/10.6084/m9.figshare.13260023.v2
  • figshare/10.6084/m9.figshare.13260056.v1

Grants and funding

This work was supported by the U.S. Department of Agriculture (USDA/MOA number 58-6404-1-637 received by RT, https://www.usda.gov/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.