Japanese researchers have
recently identified the first spontaneous mutant coral symbiont alga that does
not maintain a symbiotic relationship with its host. The alga have devised a
system where the simple addition or depletion of a nutrient can switch the
symbiosis on and off, experimentally. This alga, which is mutant, enables the
development of a genetic transformation system. This system will eventually be
a powerful tool for researchers studying coral-algal endosymbiosis.
Figure 1. Symbiotic and non-symbiotic state of the sea
anemone E.pallida, respectively.
A great source of
biodiversity in the sea is coral reefs. Stable symbiotic relationships between
host cnidarian animals and the symbiont dinoflagellate are what the ecosystem
relies on. Environmental changes due to globing warming can collapse this
symbiosis. An example of this is “coral bleaching”. Understanding mechanisms
for maintaining stable symbiosis is extremely difficult.
Figure 2. Coral Bleaching Reference
The mutant in these coral is
deficient of uracil which is a basic compound of nucleic acid. This has
appeared to have lost the ability to maintain symbiosis with a model organism.
The model organism used in this case is the sea anemone. This is what indicates
the simple addition or depletion of the nutrient which can be used as a switch
for controlling the symbiotic relationship. The next step in this research is
to introduce genetic mutations that are going to be capable of reversing uracil
deficiency in the mutant dinoflagellate. This can hopefully provide clues for
identifying algal genes responsible for symbiosis.
Source for Article and Figure 1: Tohoku University. 2018. New Mutant Coral Symbiont Alga Able to Switch Symbiosis Off. ScienceDaily. https://www.sciencedaily.com/releases/2018/02/180222103416.htm
Figure 2 Source:
http://sites.psu.edu/ichen/wp-content/uploads/sites/38297/2016/04/coralbleaching.jpg
Hayley,
ReplyDeleteThis is a very interesting find. I think that this research is a huge step in the right direction for understanding coals and their symbiotic relationships. I found the picture of the coral bleaching to be quite horrifying actually. I hope that this research helps with these sort of problems in coral reefs.
There is a paper entitled "Isolation of uracil auxotroph mutants of coral symbiont alga for symbiosis studies" that was published in February 19 of this year that deals with this issue. In the abstract, they isolated "Symbiodinum" mutants requiring uracil for growth. They cultured the bacterial cells in the presence of fluoroorotic acid (5FOA), which inhibits the growth of cells expressing URA3 encoding orotidine-5′-monophosphate decarboxylase and they isolated cells that require uracil for growth. The researchers reported that "one of the mutant cell lines had a point mutation in URA3, resulting in a splicing error at an unusual exon–intron junction, and consequently, loss of enzyme activity." This mutant could maintain a successful symbiotic relationship with the model sea anemone, but only in sea water containing uracil.
ReplyDeleteSo it seems to me that they may have identified the gene causing this. Now they just have to successfully introduce URA3 into the symbiont. I have not looked into anything after this.