The extremely reduced, diverged and reconfigured plastomes of the largest mycoheterotrophic orchid lineage

• DOI: 10.1186/s12870-022-03836-x
• Publication Date: 2022-09-20T03:33:49Z
• Authors: Yingying Wen; Ying Qin; Bingyi Shao; Jianwu Li; Chongbo Ma; Yan Liu; Boyun Yang; Xiaohua Jin
• Keywords: 0303 health sciences; Gastrodieae; Genome, Plastid; Botany; Heterotrophic Processes; 15. Life on land; Plastomes; GC contents; 03 medical and health sciences; Didymoplexis; Substitution rates; ycf1; QK1-989; Photosynthesis; Orchidaceae; Research Article

AbstractBackgroundPlastomes of heterotrophic plants have been greatly altered in structure and gene content, owing to the relaxation of selection on photosynthesis-related genes. The orchid tribe Gastrodieae is the largest and probably the oldest mycoheterotrophic clade of the extant family Orchidaceae. To characterize plastome evolution across members of this key important mycoheterotrophic lineage, we sequenced and analyzed the plastomes of eleven Gastrodieae members, including representative species of two genera, as well as members of the sister group Nervilieae.ResultsThe plastomes of Gastrodieae members contain 20 protein-coding, four rRNA and five tRNA genes. Evolutionary analysis indicated that allrrngenes were transferred laterally and together, forming anrrnblock in the plastomes of Gastrodieae. The plastome GC content ofGastrodiaspecies ranged from 23.10% (G. flexistyla) to 25.79% (G. javanica).The plastome ofDidymoplexis pallenscontains two copies each ofycf1andycf2. The synonymous and nonsynonymous substitution rates were very high in the plastomes of Gastrodieae among mycoheterotrophic species in Orchidaceae and varied between genes.ConclusionsThe plastomes ofGastrodieaeare greatly reduced and characterized by low GC content,rrnblock formation, lineage-specific reconfiguration and gene content, which might be positively selected. Overall, the plastomes of Gastrodieae not only serve as an excellent model for illustrating the evolution of plastomes but also provide new insights into plastome evolution in parasitic plants.