Download Acquisition of photosynthetic chloroplasts from algae in the Elysia

ACQUISITION OF
PHOTOSYNTHETIC
CHLOROPLASTS FROM ALGAE IN
THE ELYSIA CHLOROTICA
Olivia Archambault, John Minderman, Elizabeth
Dudley, Mackenzie Tilley, and Russell Bowles
HORIZONTAL GENE TRANSFER (HGT)
Rumpho M E et al. J Exp Biol 2011;214:303-311
INTRODUCTION
 Species
in certain phyla
capture photosynthetic
products through
symbiotic relationships
with cyanobacteria or
algae
 Consumed plastids are
located intracellularly in
the digest tract of the sea
slug.
 Certain species have
evolved traits to help
retain the plastids for
longer periods.
http://jeb.biologists.org/content/214/2/303.full#sec-2
INTRODUCTION
 Results
(Pierce et al 2012) suggest that algal
nuclear genes are present in the sea slugs and
that plastid protein and pigment turnover
necessary to sustain powers of photosynthesis
take place in the cells of E. chlorotica
 Studies have been inconclusive about the
presence of transferred genes from algae (you
are not what you eat.)
 If transferred at all, it is agreed that algal nuclear
genes will be of a very low copy number.
EXPERIMENTS
Several experiments were set out to see if E. Chlorotica
receives genes from algae to become photosynthetic.
 They explored whether nuclear gene transfer occurred, or
just plastid transfer from the algae to E. Chlorotica.

http://www.answers.com/topic/chloroplast
RESULTS
 The
researchers (Pierce et al 2012) discovered
that chloroplast encoded sequences were
present in the RNA of the sea slugs.
 101 chloroplast encoded protein coding genes
matched sequences in the algae.
 36 sequences which mapped to ribosomal
protein subunits matched between slug and algal
RNA and with chloroplast genome sequences.
RESULTS
 88
out of 111 slug transcripts in the chloroplast
encoded data sets were identical.
 In order to prevent any contamination in the
experiment, the researchers starved the slugs for
2 months to ensure that no algae was mistaken
for E. Chlorotica matter.
http://www.pbs.org/wgbh/nova/tech/algae-fuel.html
DISCUSSION
 Data
(Pierce at el 2012) shows that the
chloroplast genome is active within E. chlorotica
cells and is producing transcripts for some
chloroplast proteins.
Several transcripts found code for components of
PSI and PSII reaction centers.
 Cyt F and RuBisCO transcripts inside the slug show
that the E. chlorotica synthesize these proteins

MULTIPLE HYPOTHESES
Several experiments, conducted by Pelletreau, Wa¨gele, and Pierce,
respectively, hypothesized the following:
 That a combination of unusual plastid stability, HGT, and long-term
maintenance of cryptic algal products maintain the plastid cells.
 That there is incredible plastid longevity, but no nuclear gene
transfer, because in the feeding process no nuclear genes are
transferred maintain the plastid cells.
 That nuclear and chloroplast genes were transferred to produce
plastids and proteins in the slug.
http://wrtgfunfact.blogspot.com/2010/11/elysia-chlorotica-is-only-animal-
PROBLEMS

In the first two experiments:
They assumed, there would be a large chloroplast transcript
presence in the slug cells, as in plant cells, and would therefore
be easy to identify. But this assumption is unproven and most
likely false.
 RNA taken was from slugs that did not go through
photosynthesis and therefore most likely didn’t go through gene
transfer to make plastids
 The machines and techniques used only examined fraction of
genes, and the database they compared it to didn’t have the
algae the plastids most likely came from.


Both experiments make conclusions, either of which may still
be correct, but neither have enough data to support their
conclusion.
CONCLUSION
The first two experiments used PCR techniques, they
returned a fewer number of genes, though more
accurate, less genes were found to compare to.
 Because of the size of the DNA and protein data sets, is it
easy to find conclusion from limited data, but to prove
the solution much more sequencing is required to prove
anything.
 Therefore no correct answer is present and the data is
still inconclusive until more sequencing is done.

http://www.epochtimes.com.ua/ru/science/theory-and-research/ny-zhyvotnoe-ny-rastenye-91954.html
WORKS CITIED
Wa¨gele H, Deusch O, Ha¨ndeler K, et al. (11 co authors).
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. Mol Biol Evol. 28:699–706.
 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
