Abstract Detail


Klimpert, Nathaniel [1], Mayer, Juliana [2], Pinheiro, Fabio [2], Proscdocimi, Francisco [3], Sarzi, Diese [3], Furtado, Carolina [4], Graham, Sean [5].

Plastome structure and phylogenomics of a Brazilian mycoheterotrophic orchid, Pogoniopsis schenckii (Orchidaceae).

Mycoheterotrophic plants rely on soil-fungal associates for some or all of their carbon budget, a nutritional mode that has led to a complete loss of photosynthesis in at least 47 plant lineages, with consequences for the molecular evolution of their plastid genomes. Orchidaceae have the most losses of photosynthesis (= full mycoheterotrophy) of any plant family, with at least 26 independent origins. Only a handful of these lineages have been characterized for their plastid genomes. We sequenced the full plastid genome of Pogoniopsis schenckii, a fully mycoheterotrophic orchid, in order to characterize one of these losses, study its genome evolution, and place it more firmly in orchid phylogeny. Its plastid genome is about one-tenth the size of those of photosynthetic relatives, and is among the most reduced known. Of 12 retained protein genes that are in open reading frame, two are housekeeping genes (accD and clpP) and the rest code for ribosomal subunit genes. Two ribosomal RNA genes (16S rDNA and 23S rDNA) and two transfer RNA genes (trnfM and trnE) are also retained. AccD, clpP and trnE are part of the core set of nonbioenergetic/non-genetic apparatus genes that are commonly retained in reduced plastomes of heterotrophic plants. The trnE gene of Pogoniopsis appears to lack a functional anticodon, but likely still functions in haem biosynthesis. No retained genes have introns, and matK is missing. The plastome of P. schenckii is the most reduced one known in orchids, and is still colinear with its photosynthetic relatives. It retains an inverted repeat region, a major genome structural element commonly lost in comparably reduced plastomes. Its small and large single copy (SSC and LSC) regions are almost the same size. We present results of ongoing studies of changes in selection operating on its retained protein genes. Despite massive substitution rate elevation, phylogenomic analysis places P. schenckii in subfamily Epidendroideae with moderately strong support, corroborating a recent phylogenetic study that considered several nuclear and mitochondrial genes.

1 - University of British Columbia, Department of Botany, 6270 University Boulevard, 3200 Biological Sciences Building, Vancouver, BC, V6T1Z4, Canada
2 - Universidade Estadual de Campinas, Departamento de Biologia Vegetal, 255 Rua Monteiro Lobato, Campinas, SP, 13.083-862 , Brazil
3 - Universidade Federal do Rio de Janeiro, Instituto de Bioquímica Médica Leopoldo de Meis, Cidade Universitária - Ilha do Fundão, UFRJ/CCS/Bloco B33, Rio de Janeiro, RJ, 21.941-902, Brazil
4 - Instituto Nacional do Câncer , Divisão de Genética, 37 Rua André Cavalcanti, 4th floor, Rio de Janeiro, RJ, 20231-050, Brazil
5 - University Of British Columbia, Department Of Botany, 3529 - 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada

gene loss
Genome Evolution

Presentation Type: Oral Paper
Abstract ID:783
Candidate for Awards:None

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