title: Drastic reduction of plastome size in the mycoheterotrophic Thismia tentaculata relative to that of its autotrophic relative Tacca chantrieri.
abstract: Heterotrophic angiosperms tend to have reduced plastome sizes relative to those of their autotrophic relatives because genes that code for proteins involved in photosynthesis are lost. However, some plastid-encoded proteins may have vital nonphotosynthetic functions, and the plastome therefore may be retained after the loss of photosynthesis.
  
  
  
  We sequenced the plastome of the mycoheterotrophic species Thismia tentaculata and a representative of its sister genus, Tacca chantrieri, using next-generation technology, and we compared sequences and structures of genes and genomes of these species.
  
  
  
  The plastome of Tacca chantrieri is similar to those of other autotrophic taxa of Dioscoreaceae, except in a few local rearrangements and one gene loss. The plastome of Thismia tentaculata is ca. 16 kbp long with a quadripartite structure and is among the smallest known plastomes. Synteny is minimal between the plastomes of Tacca chantrieri and Thismia tentaculata. The latter includes only 12 candidate genes, with all except accD involved in protein synthesis. Of the 12 genes, trnE, trnfM, and accD are frequently among the few that remain in depauperate plastomes.
  
  
  
  The plastome of Thismia tentaculata, like those of most other heterotrophic plants, includes a small number of genes previously suggested to be essential to plastome survival.
authors.affiliation: The New York Botanical Garden, Pfizer Plant Research Laboratory, 2900 Southern Boulevard, Bronx, New York 10458 USA L. H. Bailey Hortorium, Section of Plant Biology, 412 Mann Library Building, Cornell University, Ithaca, New York 14853 USA gsl47@cornell.edu.
authors.forename: Gwynne S
authors.initials: GS
authors.lastname: Lim
authors.affiliation: Department of Biology, Life Sciences Building, PO Box 6057, Morgantown, West Virginia 26506 USA.
authors.forename: Craig F
authors.initials: CF
authors.lastname: Barrett
authors.affiliation: School of Biological Sciences, Kadoorie Biological Sciences Building, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Chun-Chiu
authors.initials: CC
authors.lastname: Pang
authors.affiliation: L. H. Bailey Hortorium, Section of Plant Biology, 412 Mann Library Building, Cornell University, Ithaca, New York 14853 USA.
authors.forename: Jerrold I
authors.initials: JI
authors.lastname: Davis
mesh_terms: D052818:Autotrophic Processes / Q000235:genetics*; D027743:Dioscoreaceae / Q000235:genetics*; D035264:Flowers / Q000033:anatomy & histology; D017343:Genes, Plant; D056726:Genetic Association Studies; D059646:Genome Size; D054627:Genome, Plastid; D052836:Heterotrophic Processes / Q000235:genetics*; D006723:Hong Kong; D019684:Magnoliopsida / Q000235:genetics*; D009711:Nucleotides / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D009711:Nucleotides
keywords: Dioscoreaceae; accD gene; gene loss; genome reduction; heterotrophic angiosperms; mycoheterotrophy; parasite; plastids; plastome rearrangement; plastome reduction