Abstract Detail

Phylogenomics

Lin, Qianshi [1], Stefanovic, Sasa [2].

Mitochondrial phylogenomics of mycoheterotrophic Ericaceae and parasitic Cuscuta.

Heterotrophic plants, which rely on other organism for their nutritional needs, can be particularly difficult to place in phylogeny because of substantial morphological modification, elevated substitution rates in genomes, and gene loss in the plastid genome. However, mitochondrial genes generally evolve more slowly than plastid or nuclear genes, and hence are expected to be less susceptible to long-branch artefacts in phylogenetic inference. Horizontal gene transfers from host or other organisms have also been reported in mitochondrial genomes of heterotrophic plants. Genes transferred in this fashion have usually been found non-functional. Here we report on progress in using mitochondrial genomes to infer the phylogenetic placements of mycoheterotrophic Ericaceae, and parasitic Cuscuta. We obtained the first high supported phylogeny for all five major groups of Ericaceae (i.e., core Ericaceae, pyroloids, monotropoids, arbutoids and Enkianthus). Our results show mycoheterotrophic Ericaceae are not monophyletic. Pyroloids are sister to core Ericaceae, whereas monotropoids are sister to arbutoids, indicating two separate origins of mycoheterotrophy in Ericaceae. Fungal cox1 introns, which invaded mitochondrial genomes of many angiosperms by horizontal gene transfers, occur in all mycoheterotrophic Ericaceae but are completely absent from the green ones. This pattern indicates convergent intron gains with repeated invasions from soil fungal genomes. Mitochondrial phylogeny of Cuscuta is generally consistent with previous plastid and nuclear phylogeny. However, unlike with plastid genomes, we did not find extensive gene loss in their mitochondrial genome. Our results also reveal the first example of organellar horizontal gene transfer from host to Cuscuta. Mitochondrial atp1 genes of South African section Pachystigma, were transferred from Lamiales. This inference has received high support. Conserved sequence length and open reading frame nature of it suggest these transferred genes are potentially functional.

1 - University of Toronto Mississauga, Department of Biology, Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada, Mississauga, ON, L5L 1C6, Canada
2 - University Of Toronto Mississauga, Department Of Biology, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6, Canada

Keywords:
mitochondrial genome
mycoheterotrophic plants
parasitic plants
horizontal gene transfer
Ericaceae
Cuscuta
Convolvulaceae.

Presentation Type: Oral Paper
Session: PHYLOI, Phyogenomics I
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 10:15 AM(EDT)
Number: PHYLOI002
Abstract ID:115
Candidate for Awards:None