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Abstract Detail

Comparative Genomics/Transcriptomics

Randle, Christopher P. [1], Yu, Wen-Bin [2], Morawetz, Jeffery [3], Barrett, Craig [4], dePamphilis, Claude [5].

Patterns of plastome degradation in the Aeginetieae clade of Orobanchaceae mirror those in mycorrhizal heterotrophs of Orchidaceae.

Multiple losses of photosynthetic ability have been reported in Orobanchaceae, a large family of parasitic plants: in the Orobancheae lineage, in Lathraea (toothwort), and in an obscure clade of tropical/subtropical species, the Aeginetieae. Aeginetieae includes four genera, Aeginetia and Christisonia of southeast Asia, and Harveya and Hyobanche from tropical/subtropical Africa. Aeginetieae demonstrate hallmarks of holoparasitism, most notably the reduction of structures and functions associated with photosynthesis and nutrient acquisition, including leaves reduced to scales, a lack of chlorophyll, and the absence of roots. With the evolution of holoparasitism, lack of functional constraints is thought to result in degradation of the plastome. However, Harveya retains a functional copy of the photosynthetic gene rbcL with evidence of purifying selection, indicating essential function. We have obtained plastomes for three species of Harveya, and one each from Hyobanche, Christisonia, and Aeginetia, and closely related species that are not thought to be holoparasitic. Results demonstrate a range of degradation within the genus Harveya; plastomes of Harveya huttonii and H. squamosa show little degradation (limited to pseudogene formation and loss of ndh loci), the H. scarlatina plastome also exhibits loss and pseudogenization of genes associated with photosynthesis (excluding ATP synthase genes), as well as genes encoding RNA polymerase. Gene loss and pseudogenization in Hyobanche atropurpurea exhibit similar patterns to those observed in H. scarlatina; phylogenetic analysis indicates that these changes were derived convergently. Plastomes of Christisonia and Aeginetia are severely reduced, at 51% and 37% the size of the plastome of hemiparasitic Alectra capensis, respectively. Furthermore, they exhibit pseudogenization and loss of genes important for basic expression and housekeeping functions in addition to genes associated with photosynthesis. These findings invite comparison with the general hypothesis of plastome evolution first put forth by Barrett and Davis (2012), based on patterns evident in mycorrhizal parasites of Orchidaceae.

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1 - Sam Houston State University, Department of Biological Sciences, 1900 Avenue I, Huntsville, TX, 77340, USA
2 - Xishuangbanna Tropical Botanical Garden, CAS, Center for Integrative Conservation, and Southeast Asia Biodiversity Research Institute, Mengla , Yunnan, 666303, China
3 - Rancho Santa Ana Botanic Garden, 1500 N. College Ave., Claremont, CA, 91711, USA
4 - West Virginia University, Department of Biology, 53 Campus Drive, Life Science Building, Morgantown, WV, 26506, USA
5 - Penn State University, Department of Biology, 405B Life Sciences, University Park, PA, 16802, USA

parasitic plant

Presentation Type: Oral Paper
Session: 10, Comparative Genomics and Transcriptomics
Location: Fort Worth Ballroom 5/Omni Hotel
Date: Monday, June 26th, 2017
Time: 1:30 PM
Number: 10001
Abstract ID:287
Candidate for Awards:None

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