The Making of a Photosynthetic Animal

1. The Making of a Photosynthetic Animal Group 16: Charlotte Myers, Vy Vu, Wout Moulin, Renata Bade, and Janek Witharana

2. Introduction • Can animals be photosynthetic? Elysia chlorotica (Sea Slug) Vaucheria litorea (algae)

3. Elysia chlorotica • Scientists discovered kleptoplasts (chloroplasts taken from algae) in digestive tract of Elysia chlorotica • Sea slugs photosynthesize by using kleptoplasts to sustain themselves for up to one year • Previous experiments have shown that no significant correlation exists between genes of sea slugs and kleptoplasts

4. Photosynthesis • Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. • Photosynthesis takes place in chlorophyll- containing plants, algae, and some bacteria.

5. Experiment • Hypothesis: There is a small number of transcripts for nuclear- encoded and plastid-encoded proteins present in slug cells. • Meaning: There are little similarities between the host genes and the kleptoplast genes.

6. Procedure • Established a laboratory culture system as a control • Optimized an artificial saltwater (ASW) culture system using aposymbiotic eggs • The development of the planktotrophic was recorded for all the developing larvae • The developing larvae were fed a diet of Isochrysis galbana

7. Procedure • After the larvae underwent metamorphosis the experiment could truly begin because they started eating filamentous alga, which contains plastids. • The result of metamorphosis is juvenile sea slugs • Some sea slugs ate filamentous alga • Another group did not eat filamentous alga

8. Procedure • In adulthood the sea slugs were starved • Possible photosynthetic behavior was observed in sea slugs • Genes were then compared between the matured sea slugs and chloroplasts

9. Data/Results

10. Data • Numerous functional chloroplast-encoded sequences were found in the DNA of the Elysia chlorotica • One hundred and one chloroplast-encoded protein coding genes were found in the sea slugs transcriptome which matched the sequences found in the Vaucheria litorea.

11. Data • 27 transcript sets found in the Elysia chlorotica were identical to gene coding sequences found in the Vaucheria litorea. • Among these were genes involved in photosynthesis, carbon fixation, carbohydrate metabolism, and other processes performed in chloroplasts.

12. Discussion • Contrary to the previous studies -Transcriptome of the slug contains several transcripts for nuclear-encoded algal proteins. • Symbiotic chloroplasts are translationally active and a variety of functional algal genes have been transferred into the slug genome.

13. Conclusion • Multiple approaches to kleptoplastic association understanding • Temporary function of plastids and photosynthesis • Permanent photosynthesis?

14. Clicker Question Q: Plastids such as chloroplast are eventually digested by the animal, releasing the contents of the chloroplasts’ photosynthetic reactions. In the acidic environment of a stomach, what products will be released upon the digestion of chloroplast? • Carbohydrates and O2 • NADPH and ATP • CO2 and O2 • NADPH and H2O

15. Sources • Mary E. Rumpho, Karen N. Pelletreau, Ahmed Moustafa, and Debashish Bhattacharya, 2011. The making of a photosynthetic animal. J. Exp. Biol. 214: 303-311. doi: 10.1242/​jeb.046540 • Pierce SK, Fang X, Schwartz JA, Jiang X, Zhao W, Curtis NE, Kocot KM, Yang B, Wang J. 2012. Transcriptomic evidence for the expression of horizontally transferred algal nuclear genes in the photosynthetic sea slug, Elysia chlorotica. Mol Biol Evol. 29(6):1545-56. Epub 2011 Dec 23. PubMed PMID: 22319135. doi: 10.1093/molbev/msr316 • Carter, Stein J. “Photosynthesis.” University of Cincinnati, 2000. Web. 20 October 2012. • Brahic, Catherine. “Solar-powered sea slug harnesses stolen plant genes.” New Scientist, 2008. Web. 20 October 2012.