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Faculty - Mary Rumpho-Kennedy

Phone: (207) 581-2806
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Professor of Biochemistry. As a plant physiologist/biochemist, my research focuses on the unusual endosymbiotic association between algal (Vaucheria litorea) chloroplasts and a marine mollusc (Elysia chlorotica), resulting in photosynthetic sea slugs. My lab is conducting research to characterize the symbiont plastids and demonstrate horizontal gene transfer between the algal nucleus and the sea slug. In addition, we are exploring the possibility that the sea slug produces anti-cancer metabolites as an anti-predator defense mechanism.

Education

PhD Washington State University

Research interests

Solar-Powered Sea Slugs: From Horizontal Gene Transfer to Aquaculture. The major project in my lab focuses on a unique solar-powered sea slug,Elysia chlorotica. This sea slug has evolved the means to carry out photosynthesis as a result of forming a symbiotic (kleptoplastic) association with chloroplasts it steals from its algal food source, the heterokont alga Vaucheria litorea. The captured chloroplasts (kleptoplasts) remain functional in cells lining the sea slug’s expansive digestive tract. The dark green animals subsist photoautotrophically and reproduce in culture, apart from any additional algal food source, for the duration of their normal 9 to 10 month life span. The chloroplasts have not yet been integrated into the germline, hence, the association must be established anew with each generation.

Plant Physiology coverWe have succeeded in rearing sea slugs from eggs and establishing the obligate chloroplast association by providing juvenile sea slugs with filaments of V. litorea. Uptake of chloroplasts into the expanding digestive tract and development of the animal were recorded with video-and still-microscopy. To date, no algal nuclei have been detected within the cells of the mollusc. This begs one to ask how oxygenic photosynthesis can be maintained without the large number of chloroplast proteins encoded in the genes of the algal nucleus. In an attempt to find these genes elsewhere, we first sequenced the chloroplast genome of V. litorea, but it revealed no unusual coding capacity to suggest any greater autonomy of these chloroplasts than other secondary endosymbionts. We are now focused on identifying if algal nuclear genes encoding chloroplast proteins have been transferred from the alga to the sea slug over the course of evolution. We have targeted the Calvin Cycle enzyme phosphoribulokinase (PRK), and the manganese stabilizing protein (MSP, psbO), an essential component of the photosystem II oxygen evolving complex. Using PCR and RT-PCR and V. litoreahomologous primers, we were able to demonstrate the presence and expression of both genes in sea slugs and sea slug eggs with very high similarity to the corresponding algal sequences. Two copies of prk were detected in sea slug DNA and cDNA, one with and one without an intronic sequence found in the algal genomic prk sequence. We are currently employing genome walking to identify the flanking genomic DNA for both genes and sequencing the mtDNA of the sea slug to provide further evidence for HGT, and demonstrate where/how the DNA has been integrated within its new host.

Fascinating organisms like these “solar-powered sea slugs” can transform the teaching of basic principles in biology. We are exploiting the sea slugs in the development of multimedia educational materials disseminated through an interactive website (http://sbe.umaine.edu/symbio/), and partially funded by the American Society of Plant Biologists and the Maine Technology Institute. Culturing of the sea slugs will ultimately provide a supply of this unusual organism for classrooms and laboratories, marine aquaria hobbyists, and contributes to protection of a rare species and its native habitat.

Elysia chlorotica and Vaucheria litorea

Elysia chlorotica and Vaucheria litorea. A) Dorsal view of E. chlorotica. Animals are typically found in nature as small as 1 or 2 cm to as large as 6 cm, as shown here. B) Ventral view of E. chlorotica. C) Two camouflaged E. chlorotica specimens feeding on V. litorea. D) Several specimens of E. chlorotica showing the variation in size and body forms. E) V. litorea filaments (about 1 to 2 mm diameter). F) Sea slugs are easily cultured in aquaria containing full-strength artificial sea water and overhead lighting at 10°C. Non-pigmented eggs are produced in a mucus mass on the aquaria walls (see arrow). The eggs serve as a source of pure animal DNA since no plastids are found in the eggs.

Biosynthesis of Natural Anticancer Compounds in Molluscs. The sea slug Elysia chlorotica is also being exploited for its natural production of anticancer compounds as a predatory defense. Several species of ascoglossan molluscs, including members of the algal feeding genus Elysia, have been shown to synthesize and accumulate toxic secondary metabolites in their mucus which they subsequently can secrete in large amounts as a defense mechanism.  Some of these compounds have been shown to possess anticancer activity and one of these, a cyclic depsipeptide named kahalalide F, is in preclinical lung and colon cancer trials by PharmaMar in Spain. We are exploring extracts of the sea slugs and copious mucus produced by E. chlorotica to identify any secondary metabolites which may exhibit antifungal or anticancer properties against human cancer cell lines.  If such metabolites are found, the algal food source Vaucheria litorea, will also be analyzed as well as sea slug eggs which are devoid of any plastids.  This will tell us if synthesis of the toxic metabolites is dependent on the symbiotic association with the plastids and perhaps a driving force behind the symbiotic evolutionary adaptation.

New England Invasive Plant CenterNew England Invasive Plant Center. A second project area in my lab focuses on noxious invasive plants which cause at least a $35 billion loss per year to the U.S. economy. This figure is increasing at a rate of 10% annually. Because of the urgent need for new and effective approaches to address the serious problem of invasive plants, which include many ornamental crops, the University of Maine, the University of Connecticut, and the University of Vermont requested and received funding from the USDA to establish a multi-state, interdisciplinary New England Invasive Plant Center. Using its strength in developing non-invasive ornamental plants, the Center is focused on novel strategies to manage problems caused by invasive plants that are economically and environmentally damaging to the Northeastern U.S. and to the nation as a whole. The proposed objectives for the Center are: 1) Development of non-invasive sterile landscape plants. 2) Assessment of the ecological impact of invasive plants and ecological evaluation of new “super-sterile” cultivars. 3) Assessment of the economic impact of invasive species in New England and 4) Development of alternative native crops.

Publications

  • Rumpho ME, JM Worful, J Lee, K Kannan, MS Tyler, D Bhattacharya, A Moustafa and JR Manhart 2008 Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica. Proceedings of the National Academy of Sciences USA 105:17867-17871
  • Rumpho ME, FP Dastoor, JR Manhart and J Lee 2006 The Kleptoplast. In: Advances in Photosynthesis and Respiration – The Structure and Function of Plastids. RR Wise and JK Hoober, eds, Springer Pub., Vol. 23, pp 451-473
  • Pennisi E 2006 Plant Wannabes. Science 313:1229
  • Green BJ, TC Fox, JR Manhart and ME Rumpho 2005 Stability of isolated chromophytic algal chloroplasts that participate in a unique molluscan/algal endosymbiosis. Symbiosis 40:31-40
  • Rumpho ME, EJ Summer, BJ Green, TC Fox and JR Manhart 2001 Mollusc/algal chloroplast symbiosis: How can isolated chloroplasts continue to function for months in the cytosol of a sea slug in the absence of an algal nucleus? Zoology 104:303-312
  • Rumpho ME and JR Manhart 2001 Elysia chlorotica and Vaucheria litorea: Symbiosis between a mollusc and algal plastids produces solar-powered sea slugs. ISS Symbiosis Inernational, Vol. 1, No. 2
  • Rumpho ME, JR Manhart and EJ Summer 2000 Solar-Powered Sea Slugs. Mollusc/algal chloroplast symbiosis. Plant Physiology 123:29-38 http://www.plantphysiol.org/cgi/content/full/123/1/29
  • Green BJ, W-y Li, JR Manhart, TC Fox, EJ Summer, RA Kennedy, SK Pierce and ME Rumpho 2000 Mollusc-algal chloroplast endosymbiosis: photosynthesis, thylakoid protein maintenance, and chloroplast gene expression continue for many months in the absence of the algal nucleus. Plant Physiology 124:331-342 http://www.plantphysiol.org/cgi/content/abstract/124/1/331
  • Nolte BA and ME Rumpho 2000 Rapid micro-assay of camptothecin in Camptotheca acuminata. Planta Medica 67: 376-378
  • Pierce SK, TK Maugel, ME Rumpho, JJ Hanten and WL Mondy 1999 Annual viral expression in a sea slug population: Life cycle control and symbiotic chloroplast maintenance. Biological Bulletin 197:1-6
  • Mujer CV, DL Andrews, JR Manhart, SK Pierce and ME Rumpho 1996 Chloroplast genes are expressed during intracellular symbiotic association of Vaucheria litorea plastids with the sea slug Elysia chlorotica. Proceedings of the National Academy of Sciences USA 93:12333-12338 View the PDF here
  • Pierce SK, RW Biron and ME Rumpho 1996 Endosymbiotic chloroplasts in molluscan cells contain proteins synthesized after plastid capture. Journal of Experimental Biology 199:2323-2330
  • Rumpho ME, CV Mujer, DL Andrews, JR Manhart and SK Pierce 1994 Extraction of DNA from mucilaginous tissues of a sea slug (Elysia chlorotica). BioTechniques 17:1097-1101
  • D’Appollonio J, LB Stack, M Rumpho and D Zhang 2006 Is burningbush invading your woodlot? SWOAM News. Vol 31 No 8, pp 10-11
  • D’Appollonio J, LB Stack, M Rumpho and D Zhang 2006 A volunteer opportunity: help us determine if burningbush is invasive in Maine. Maine Master Gardener News. The University of Maine Cooperative Extension pub., July


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