Retention of an apparently functional plastome in an apparently mycoheterotrophic orchid, Dipodium roseum D.L.Jones & M.A.Clem. (Orchidaceae)

Context Giving up photosynthetic function is a bold evolutionary step for plant, yet the transition from autotrophy to mycoheterotrophy has occurred dozens of times. Comparing plastome sequences mycoheterotrophs and autotrophs identified recurring patterns gene loss throughout range land plants, though more comparisons are required see how broadly these apply across diversity terrestrial plants. Mycoheterotrophy especially common in Orchidaceae, with than 40 transitions family.Aims We sought test generalised degradation seen other by comparing two species genus Dipodium (Orchidaceae); one appears be facultative mycoheterotroph species.Methods sequenced assembled plastomes compared genomes identify or loss.Results The were nearly identical, no photosynthesis genes putative mycoheterotroph, both have undergone pseudogenisation all plastid ndh (nicotinamide adenine dinucleotide + hydrogen specific dehydrogenase) genes.Conclusions These results contrast most between likely mycoheterotrophic relatives, where rapid common, may suggest leafless capable early stages transitioning fully heterotrophic lifestyle.Implications Further investigation trophic Dipodium, including sequencing measuring capability heterotrophs, will yield insights into evolution plant lineages that lose ability photosynthesise.