Evolutionary Patterns of the Chloroplast Genome in Vanilloid Orchids (Vanilloideae, Orchidaceae)

Young Kee Kim, Se Hwan Cheon, Ja Ram Hong, Ki Joong Kim

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1 Citation (Scopus)

Abstract

The Vanilloideae (vanilloids) is one of five subfamilies of Orchidaceae and is composed of fourteen genera and approximately 245 species. In this study, the six new chloroplast genomes (plastomes) of vanilloids (two Lecanorchis, two Pogonia, and two Vanilla species) were decoded, and then the evolutionary patterns of plastomes were compared to all available vanilloid plastomes. Pogonia japonica has the longest plastome, with 158,200 bp in genome size. In contrast, Lecanorchis japonica has the shortest plastome with 70,498 bp in genome size. The vanilloid plastomes have regular quadripartite structures, but the small single copy (SSC) region was drastically reduced. Two different tribes of Vanilloideae (Pogonieae and Vanilleae) showed different levels of SSC reductions. In addition, various gene losses were observed among the vanilloid plastomes. The photosynthetic vanilloids (Pogonia and Vanilla) showed signs of stage 1 degradation and had lost most of their ndh genes. The other three species (one Cyrotsia and two Lecanorchis), however, had stage 3 or stage 4 degradation and had lost almost all the genes in their plastomes, except for some housekeeping genes. The Vanilloideae were located between the Apostasioideae and Cypripedioideae in the maximum likelihood tree. A total of ten rearrangements were found among ten Vanilloideae plastomes when compared to the basal Apostasioideae plastomes. The four sub-regions of the single copy (SC) region shifted into an inverted repeat (IR) region, and the other four sub-regions of the IR region shifted into the SC regions. Both the synonymous (dS) and nonsynonymous (dN) substitution rates of IR in-cooperated SC sub-regions were decelerated, while the substitution rates of SC in-cooperated IR sub-regions were accelerated. A total of 20 protein-coding genes remained in mycoheterotrophic vanilloids. Almost all these protein genes show accelerated base substitution rates compared to the photosynthetic vanilloids. Two of the twenty genes in the mycoheterotrophic species faced strong “relaxed selection” pressure (p-value < 0.05).

Original languageEnglish
Article number3808
JournalInternational journal of molecular sciences
Volume24
Issue number4
DOIs
Publication statusPublished - 2023 Feb

Bibliographical note

Funding Information:
This work was supported by the National Institute of Biological Resources (NIBR) under the genetic evaluation of vascular plants IV-1 (2018, grand no. NIBR201803102) to K.-J.K. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (2020R1A6A3A01100512) to Y.-K.K.

Publisher Copyright:
© 2023 by the authors.

Keywords

  • Orchidaceae
  • SSC contraction
  • Vanilloideae
  • gene loss
  • gene relocation
  • plastomes

ASJC Scopus subject areas

  • Catalysis
  • Molecular Biology
  • Spectroscopy
  • Computer Science Applications
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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