Abstract Detail

Genomics / Proteomics

Lam, Vivienne K. Y. [1], Merckx, Vincent [2], Yukawa, Tomohisa [3], Wulff, Adrien [4], Hollingsworth, Michelle [5], Hollingsworth, Peter [5], McNair, Daniel [6], Graham, Sean W. [7].

Parallel degradation of plastid genomes in diverse lineages of mycoheterotrophic plants.

Multiple lineages of land plants have become reliant on mycorrhizal or saprophytic fungi for their fixed carbon and other nutrients. This major shift in the mode of plant nutrition has been associated with repeated losses of photosynthesis in distantly related taxa, events that are analogous to (but more frequent than) the parallel losses observed in parasitic plants. We expect that relaxation of selection in photosynthetic and other genes led to convergent changes in mycoheterotrophic plastid genomes (plastomes), including serial bouts of pseudogenization and gene loss. We also expect a subset of plastid genes to be retained even in highly modified mycoheterotrophs (e.g. “housekeeping” or plastid genetic apparatus genes), and recent studies have also reported retentions of a subset of photosynthesis genes serving additional roles in plant metabolism. The goal of our study is to understand general and specific patterns of plastome evolution associated with the loss of photosynthesis in mycoheterotrophic plants. We have recovered and characterized complete plastomes from multiple mycoheterotrophic lineages, that reflect independent instances of plastome degradation. Contigs were derived from genome-survey sequences, and we closed the circular plastid genomes using PCR and Sanger sequencing. Assemblies of full circular plastomes include multiple representatives of mycoheterotrophic monocots: Burmanniaceae (from four genera), Corsiaceae (two genera) and Petrosaviaceae (several species), in addition to mycoheterotrophic representatives of Iridaceae and Triuridaceae. We also report on the heterotrophic conifer Parasitaxus usta (Podocarpaceae). In addition to characterizing patterns of gene loss, we examined genome structural changes by comparing heterotrophic plastomes to those of closely related autotrophs. Some taxa appear to have a gene order for retained genes that is consistent with their green relatives, while others have more rearranged genomes. We observed a variety of rearrangements, including expansion, reduction, modification and loss of inverted repeat (IR) regions. We also observed substantial variation among closely related mycoheterotrophic species in the degree of gene loss and rearrangement, some of which may have resulted from independent genome rearrangements following a shared ancestral loss of photosynthesis. An additional goal is to use the current data to help place mycoheterotrophic lineages in a phylogenetic context, and so we also report on the placement of the mycoheterotrophic taxa in a monocot-wide phylogenetic analyses.

1 - University of Britsh Columbia, Department of Botany, Biodiversity Research Centre, 2212 Main Mall, Vancouver, BC, V6T 1Z4, Canada
2 - Biology, M.H. Tromplaan 152, Oegstgeest, N/A, 2341TE, Netherlands
3 - National Museum Of Nature And Science, Department Of Botany, 1-1, Amakubo 4, Tsukuba, N/A, 305-0005, Japan
4 - Université de la Nouvelle-Calédonie, Laboratoire Insulaire du Vivant et de l'Environnement, n/a, Nouméa, 98851, New Caledonia
5 - Royal Botanic Garden Edinburgh, Edinburgh, EH3 5LR, UK
6 - University Of Southern Mississippi, Department Of Biological Sciences, 118 College Drive #5018, Hattiesburg, MS, 39406-0001, USA
7 - University of British Columbia, Department of Botany, 3529 - 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada

Keywords:
Mycoheterotrophy
plastid genome
Genome Evolution.

Presentation Type: Oral Paper:Papers for Topics
Session: 35
Location: Pines South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 10:45 AM
Number: 35011
Abstract ID:537
Candidate for Awards:None