title: Plastomes on the edge: the evolutionary breakdown of mycoheterotroph plastid genomes.
abstract: Contents 48 I. 48 II. 50 III. 53 54 References 54 SUMMARY: We examine recent evidence for ratchet-like genome degradation in mycoheterotrophs, plants that obtain nutrition from fungi. Initial loss of the NADH dehydrogenase-like (NDH) complex may often set off an irreversible evolutionary cascade of photosynthetic gene losses. Genes for plastid-encoded subunits of RNA polymerase and photosynthetic enzymes with secondary functions (Rubisco and ATP synthase) can persist initially, with nonsynchronous and quite broad windows in the relative timing of their loss. Delayed losses of five core nonbioenergetic genes (especially trnE and accD, which respectively code for glutamyl tRNA and a subunit of acetyl-CoA carboxylase) probably explain long-term persistence of heterotrophic plastomes. The observed range of changes of mycoheterotroph plastomes is similar to that of holoparasites, although greater diversity of both probably remains to be discovered. These patterns of gene loss/retention can inform research programs on plastome function.
authors.affiliation: Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Graham
authors.affiliation: Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Vivienne K Y
authors.initials: VK
authors.lastname: Lam
authors.affiliation: Understanding Evolution Group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, the Netherlands.
authors.forename: Vincent S F T
authors.initials: VS
authors.lastname: Merckx
mesh_terms: D019143:Evolution, Molecular; D005658:Fungi / Q000502:physiology*; D054627:Genome, Plastid; D052836:Heterotrophic Processes / Q000235:genetics*; D008957:Models, Genetic; D010788:Photosynthesis / Q000235:genetics
keywords: comparative genomics; convergent evolution; mixotrophy; mycoheterotrophic plants; photosynthesis genes; plastid function; plastid translation apparatus