Horizontal transfer of genes (HTG) is one of the most interesting and controversial aspects of Elysia biology.  In order to maintain kleptoplasts for many months, components need to be synthesized to replace those that are lost over time.  Because one would not expect chloroplast-related genes to be part of a molluscan genome, where would they come from.  For a while, it looked as though some algal genes had been incorporated into the slugs’ genomes, which could a rare example of HTG between multicellular organisms.  However, as can be seen from the most recent papers on HTG in Elysia, it appears doubtful that any such events have occurred.

Maeda T, Takahashi S, Yoshida T, Shimamura S, Takaki Y, Nagai Y, Toyoda A, Suzuki Y, Arimoto A, Ishii H, Satoh N, Nishiyama T, Hasebe M, Maruyama T, Minagawa J, Obokata J, Shigenobu S. (2021) Chloroplast acquisition without the gene transfer in kleptoplastic sea slugs, Plakobranchus ocellatus. Elife. 10: e60176.  [K] [Pl]

Cai H, Li Q, Fang X, Li J, Curtis NE, Altenburger A, Shibata T, Feng M, Maeda T, Schwartz JA, Shigenobu S, Lundholm N, Nishiyama T, Yang H, Hasebe M, Li S, Pierce SK, Wang J. (2019) A draft genome assembly of the solar-powered sea slug Elysia chlorotica. Sci Data. 6: 190022. [HT] [K] [Ch]

Bhattacharya, D., Pelletreau, K.N., Price, D.C., Sarver, K.E., Rumpho, M.E.(2013) Genome analysis of Elysia chlorotica egg DNA provides no evidence for horizontal gene transfer into the germ line of this kleptoplastic mollusc Molecular Biology and Evolution, 30 (8), pp. 1843-1852. PDF [HT] [K] [Ch]

Middlebrooks, M.L., Bell, S.S., Pierce, S.K. (2012) The kleptoplastic sea slug Elysia clarki prolongs photosynthesis by synthesizing chlorophyll a and b. Symbiosis, 57 (3), pp. 127-132. Page1 [HT] [K] [Cl]

Pierce, S.K., Fang, X., Schwartz, J.A., Jiang, X., Zhao, W., Curtis, N.E., Kocot, K.M., Yang, B., Wang, J. (2012) Transcriptomic evidence for the expression of horizontally transferred algal nuclear genes in the photosynthetic sea slug, Elysia chlorotica. Molecular Biology and Evolution, 29 (6), pp. 1545-1556. PDF [HT] [K] [Ch]

Soule, K.M., Rumpho, M.E. (2012) Light-regulated photosynthetic gene expression and phosphoribulokinase enzyme activity in the heterokont alga Vaucheria litorea (xanthophyceae) and its symbiotic molluskan partner Elysia chlorotica (gastropoda). Journal of Phycology, 48 (2), pp. 373-383. Abstract [HT] [K] [Ch]

Wägele, H., Deusch, O., Händeler, K., Martin, R., Schmitt, V., Christa, G., Pinzger, B., Gould, S.B., Dagan, T., Klussmann-Kolb, A., Martin, W. (2011) Transcriptomic evidence that longevity of acquired plastids in the photosynthetic slugs Elysia timida and Plakobranchus ocellatus does not entail lateral transfer of algal nuclear genes. Molecular Biology and Evolution, 28 (1), pp. 699-706. PDF [HT] [K] [Ti]

Rumpho, M.E., Pelletreau, K.N., Moustafa, A., Bhattacharya, D. (2011) The making of a photosynthetic animal. Journal of Experimental Biology, 214 (2), pp. 303-311. PDF [HT] [K] [NH] [Ch]

Skulachev, V.P. (2010) Discovery of a photosynthesizing animal that can survive for months in a light-dependent manner. Biochemistry (Moscow), 75 (12), pp. 1498-1499. PDF [HT] [K] [R] [Ch]

Schwartz, J.A., Curtis, N.E., Pierce, S.K. (2010) Using algal transcriptome sequences to identify transferred genes in the sea slug, Elysia chlorotica. Evolutionary Biology, 37 (1), pp. 29-37. PDF [HT] [K] [Ch]

Pierce, S.K., Curtis, N.E., Schwartz, J.A. (2009) Chlorophyll a synthesis by an animal using transferred algal nuclear genes. Symbiosis, 49 (2), pp. 121-131.PDF [HT] [K] [Ch]

Rumpho, M.E., Pochareddy, S., Worful, J.M., Summer, E.J., Bhattacharya, D., Pelletreau, K.N., Tyler, M.S., Lee, J., Manhart, J.R., Soule, K.M. (2009) Molecular characterization of the calvin cycle enzyme phosphoribulokinase in the stramenopile alga Vaucheria litorea and the plastid hosting mollusc Elysia chlorotica. Molecular Plant, 2 (6), pp. 1384-1396. PDF [HT] [K] [Ch]

Rumpho, M.E., Worful, J.M., Lee, J., Kannan, K., Tyler, M.S., Bhattacharya, D., Moustafa, A., Manhart, J.R. (2008) Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica. Proceedings of the National Academy of Sciences of the United States of America, 105 (46), pp. 17867-17871. PDF [HT] [K] [Ch]

Pierce, S.K., Curtis, N.E., Hanten, J.J., Boerner, S.L., Schwartz, J.A. (2007) Transfer, integration and expression of functional nuclear genes between multicellular species. Symbiosis, 43 (2), pp. 57-64. [HT] [K] [Ch]

Hanten, J.J., Pierce, S.K. (2001) Synthesis of several light-harvesting complex I polypeptides is blocked by cycloheximide in symbiotic chloroplasts in the sea slug, Elysia chlorotica (Gould): A case for horizontal gene transfer between alga and animal? Biological Bulletin, 201 (1), pp. 34-44.  PDF [K] [HT] [Ch]

Rumpho, M.E., Summer, E.J., Green, B.J., Fox, T.C., Manhart, J.R. (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 (3-4), pp. 303-312. Abstract [HT] [K] [Ch]

Green, B.J., Li, W.-Y., Manhart, J.R., Fox, T.C., Summer, E.J., Kennedy, R.A., Pierce, S.K., Rumpho, M.E. (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 (1), pp. 331-342. Abstract PubMedCentral PDF [HT] [K] [Ch]

Mujer, C.V., Andrews, D.L., Manhart, J.R., Pierce, S.K., Rumpho, M.E. (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 of the United States of America, 93 (22), pp. 12333-12338. PubMedCentral PDF [HT] [K] [Ch]

Pierce, S.K., Biron, R.W., Rumpho, M.E. (1996) Endosymbiotic chloroplasts in molluscan cells contain proteins synthesized after plastid capture. Journal of Experimental Biology, 199 (10), pp. 2323-2330.  PDF [HT] [K] [Ch]