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The evolution and expression of rbcL in holoparasitic sister genera, harveya hook. and hyobanche l. (orobanchaceae) and systematics and taxonomic revision of southern African species of harveya

Randle, Christopher P.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1085582568

Abstract Details

2004, Doctor of Philosophy, Ohio State University, Evolution, Ecology, and Organismal Biology.
The evolution of holoparasitism in plants is often accompanied by reduction in structures and functions associated with photosynthesis and nutrient acquisition. This reduction in morphological and anatomical features occurs concomitantly with loss or truncation of photosynthesis-related genes freed from selective constraints. The chloroplast genome of many holoparasitic plants is drastically reduced in both the quantity and quality of genetic material. Harveya and Hyobanche (Orobanchaceae) are holoparasitic genera native to southern Africa. Hyobanche has undergone pseudogene formation at the chloroplast locus encoding the large subunit of the carbon-fixing holoenzyme Rubisco, rbcL, while Harveya maintains a seemingly functional copy of this gene, which is evolving under purifying selection. The regions flanking rbcL, the 5’- and 3’- Untranslated Regions, appear to be functional in both genera. However, Western blot analysis shows that the large subunit is present in both taxa, despite the presence of the pseudogene in Hyobanche. This may be explained by two hypotheses: 1) multiple copies of rbcL exist in Hyobanche, one of which codes for a functional protein, or 2) RNA transcripts are repaired by an as-yet unknown mechanism. Cloning and RNA experiments demonstrated that while there are indeed multiple copies of rbcL in Hyobanche, none of these codes for a functional protein. The hypothesis that Rubisco is obtained from host plants is discussed, as well as other possible functions of Rubisco in these putatively non-photosynthetic plants. Of 53 species names attributed to the genus Harveya, 35 represent species endemic to southern Africa. However, the genus has never been treated as a whole taxonomically, and the southern African species have not been revised since Hiern’s treatment of 1904. Species delimitations were reassessed using material collected in the field as well as specimens borrowed from herbaria, resulting in the reduction of the genus to twelve species native to southern Africa. A diagnostic key for identification of species was presented, and host-plant records, habitat, and geographical distributions were summarized for each species circumscribed. Molecular sequence data from the chloroplast and nucleus were used to test hypothesized relationships among these species, and the evolution of floral characteristics, host-plant ranges, and geographical origins.
Andrea Wolfe (Advisor)
243 p.
Harveya; Hyobanche; parasitic plants; rbcL; ITS nrDNA; systematics; molecular evolution; Orobanchaceae; taxonomy; phylogenetics; Rubisco; cpDNA

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Citations

  • Randle, C. P. (2004). The evolution and expression of rbcL in holoparasitic sister genera, harveya hook. and hyobanche l. (orobanchaceae) and systematics and taxonomic revision of southern African species of harveya [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1085582568

    APA Style (7th edition)

  • Randle, Christopher. The evolution and expression of rbcL in holoparasitic sister genera, harveya hook. and hyobanche l. (orobanchaceae) and systematics and taxonomic revision of southern African species of harveya. 2004. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1085582568.

    MLA Style (8th edition)

  • Randle, Christopher. "The evolution and expression of rbcL in holoparasitic sister genera, harveya hook. and hyobanche l. (orobanchaceae) and systematics and taxonomic revision of southern African species of harveya." Doctoral dissertation, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1085582568

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.