Predicting Acropora millepora Genetic Tolerance Towards Bleaching

 

Anthropogenic climate change is creating warmer temperatures in the oceans and for certain coral reefs when temperatures remain above a sustainable level for extended periods of time, coral bleaching occurs. This study used genomic-wide patterns of variation to predict bleaching responses across a distribution for coral conservation. Coral reefs consist of a symbiotic relationship between the coral itself and intracellular photosynthetic dinoflagellates that provide energy for the coral. During coral bleaching the coral becomes intolerant to the heat and the dinoflagellates of the Symbiodiaceae family are expelled from the coral and if the coral does not take these dinoflagellates back in after an extended period of time the coral dies. This study looked at Acropora millepora, a common reef-building coral, that is widely distributed across the Indo-Pacific Ocean that potentially can have significant genetic diversity between populations that are better adapted to warming sea temperatures. There were 237 samples of chromosomal data taken from 12 different reefs in the central Great Barrier Reef. Heat tolerance in coral is not fully understood if it is polygenic or influenced by some common large-effect loci. The only loci found in this genomic-wide association was a long-term balancing selection in heat-shock and it is called sacsin. Sacsin is a co-chaperone for the heat tolerance protein Hsp70 and this helps the coral adjust to warmer temperatures over a long period of time; however, recently due to anthropogenic impacts the changes in temperature have been fast and short-term periods. This locus is found in the genus of corals Acropora and Pocillipora and the sequence of sacsin has been maintained with little to no variation across millions of generations, so any variation detected in this gene will suggest adaptation for the balancing selection for increasing heat. There was little haplotype diversity across the chromosomal scale for genomic-wide association due to the broadcast spawning mode of reproduction in A. millepora. This indicates that coral bleaching responses are not due a common locus across a genome, which supports that the phenotype of coral bleaching is polygenic and individual coral populations responses to warmer temperatures can be predicted instead of across a whole genome.

https://www.science.org/doi/pdf/10.1126/science.aba4674?casa_token=d0li8PfomAAAAAAA:miMxO9bXbcN24--RzDA7jImRn7OvnUzPXHcm2JtGWQNKY7IAtA9m86EwfTKuZd7LksEObveIzMfp4Mk

https://oceanservice.noaa.gov/facts/coral_bleach.html

https://www.nature.com/scitable/topicpage/polygenic-inheritance-and-gene-mapping-915/

The Influence of Mitochondrial DNA Heteroplasmy in Green Sea Turtles

 

In this study heteroplasmy genotyping of green sea turtles, Chelonia mydas, using high throughput sequencing (HTS) was used to better understand SNP and mtSTR in the mitochondrial genome and its variation within individuals across generations. HTS allows for the observing of mtDNA on the repeating the D-loop, which is not under strong selective pressure. Heteroplasmy is the existence of mitochondrial DNA (mtDNA) variant within a cell. Mitochondrial DNA is 0.001% of genomic content and due to oxidative phosphorylation, mutations that occur in mtDNA are directly associated to inherited diseases. Since heteroplasmy deals with variation in mtDNA the haplotypes passed down to generations, the mtDNA comes from maternal inheritance. Population sizes green turtles will determine the variation in haplotypes especially depending on the amount of female turtle populations. The maternal inheritance of mtDNA has a large influence on heteroplasmy due to the number of mitochondria passed, the DNA inherited and mutations along with it. Due to mtDNA being only maternally inherited and the low population sizes of green turtles, the passed down mtDNA has low genetic diversity, low mutation rates, and low rates of new generations. A shift in haplotypes from maternal inheritance will signal genetic bottlenecking during oogenesis meaning heteroplasmy will increase with larger populations and decrease in diversity with smaller populations. This study found haplotypes in individuals of green turtles in foraging grounds more than nesting sights meaning there mixing of stocks and the HTS revealed that heteroplasmy is low in frequency among these individuals.

https://www.nature.com/articles/s41598-019-56918-6.pdf

https://pubmed.ncbi.nlm.nih.gov/22578655/

https://pubmed.ncbi.nlm.nih.gov/17391067/

https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/high-throughput-sequencing

Scientists Find 13 Candidate Genes Associated with Fitness Outcomes

In this article researchers found that there is a specific type of gene called candidate gene may be able to predict successful responses from targeted types of workouts within peoples training as well as influence energy pathways. metabolism, storage and cell growth in the body. A meta-analysis was conducted to find specific versions or alleles of the candidate genes in relation to untrained participants response to exercise and analyzed strength, anaerobic power, as well as cardiopulmonary fitness. The study was also able to tell wether it was identified genes or alleles which was the contributor to differences within exercise training responses within the participants of the study. Researchers had been able to identify 13 candidate genes and alleles from which there were nine, six, and four that were correlated with cardiorespiratory fitness, muscular strength, as well as anaerobic power. When breaking down these three categories, it was interpreted that 44% of the difference in aerobic training responses were due to genetic influences. Within the power group genes had less influence with only having 10% of the variability in response to being due to genetics. As researchers learn more about phenotypic expressions of the various haplotypes within genes there will eventually be a spectrum to help interpret them moving froward. The meta- analysis was able to classify the study groups, however further studies will have to find out the exact role of the genes influencing cardiopulmonary fitness, strength and anaerobic power. The benefit of finding the exact role will help to better support the optimization and individualization for exercise programs based on the genetic makeup of a person.

Insights Into the Koala’s Genetic Challenge

In the NY Times Koalas have been studied by many scientists in regards to their genetic diversity. One main poit is that these animals have been said to have a very low genetic diversity. At first the thought of the 19t century fur trade could have been the reason for the declined population of koalas. When doing further research, there has been more of this low genetic diversity to have been due to from awhile into the past.

[caption id="attachment_5765" align="aligncenter" width="190" caption="Koala"][/caption]

Before the fur-trapping incidents in Australia there has been much more of a reason for the decline in these animals. Koalas have been continuously known in facing a disease which is known as koala retrovirus, also known as KoRV. This is compared closely H.I.V., which goes hand in hand with chlamydia. This has been going on for years throughout the koala species. The koalas are unable to adapt to their environment due to a gene variation which was further looked into by scientists. The scientists looked up DNA from fourteen different koala specimens. Throughout the koalas there has been a common haplotype. There is a unique sequence of mitochondrial DNA that has not been any different since the year of 1870. Modern day koalas have had the same uniqueness among them compared to the koalas in the past. The KoRV was also similarly found in the koalas from the past as well as the modern day ones. This made the assumption that there could have been a genetic drift occurred from a much longer time ago. The hunting could have definitely had an effect but another reason from the past could have been a more major reason.

[caption id="attachment_5767" align="aligncenter" width="370" caption="Koala Fur Trade (moved to Queensland at the time)"][/caption]

Hopefully more research can be done by scientists to figure out whether or not a type of gene therapy can be provided for these animals. Further investigations are being made in order to find koalas free from this virus. Possibly there can be a healthier genetic diversity among the koalas.