Transcript – Investigating the Potential for Inter-Generational Effects of Temperature Stress on Blow Flies

Hello, my name is Aaron Tarone. I would like to thank you for coming to our poster on the intergenerational effects of thermal stress on blowflies.

Before I start, I’d like to acknowledge Abigal who’s the grad student that has been doing the work associated with this T3 project. And we would also like to acknowledge our valued colleague, Cliff Spiegelman, who unexpectedly passed away this summer. Cliff has worked with me and Jeff Tomberlin on a number of projects related to blowfly biology as they relate to forensic science and this T3 grant was precipitated in part on his interest in epigenetics in the system. And so Cliff is a respected colleague that did a lot of work in the forensic science community to establish standards in the field. We appreciated his work with us on blowfly biology specifically, and he will be missed.

Ok, so why would you study a blowfly?

Well, there are a number of reasons and they all, for us, centered around the fact that blowflies are the ones that we’re interested in, uh, feed on animal remains. And so if you’re interested in basic ecosystem processes like nutrient recycling, an animal dies, these flies show up, they lay eggs on their remains, and those immature flies remove a lot of the biomass from your remains and return it back to the ecosystem. However, a consequence of the biology of these lines that they’re associated with disease ecology and forensic science, so decomposing animal remains are replete with bacteria and other microbes, several which are pathogens. And there is interest in understanding the role of these flies and the ecology of diseases associated with. And in forensic science, these flies, because they’re adapted to exploiting remains rapidly, they can show up within minutes or hours of death. People use the predictable development of these fires as a biological clock to provide temporal information and death investigations.

And so in this case, the predictability of development becomes important. And so one of the things that you want to think about when you have a developing organism is that this is a quantitative trait. Quantitative traits can be affected by genetics or the environment. So if you’re trying to make a good forensic prediction and you want to understand uncertainty, you should have a handle on the genetics and the environmental contributions to your trade. But even an ecological sense, the relative impact of genetics versus the environment may alter the way nutrients recycle the environment. So much of the biology of these flies that’s interesting to us is associated with development time. And so that’s why we’re studying this tree and specific. And what we’re curious about is if there are impacts of thermal stress on the way that genetics impacts the resulting phenotype. So if you have a male flying female flatmate, they produce offspring and do their offspring look like the average of those parents or they look nothing like the average of those parents? And so you can imagine, for instance, in a forensic prediction that that might be very important for making your estimate. So quantity quantitative geneticists study these traits, these sorts of traits using a concept called heritability, where if you were to take two parents of a known phenotypes are so known development times and made them then evaluate their offspring and you see what the phenotype score for the offspring is. If that regression of parent against offspring has a slope of one, then you would consider the heritability to be one, and that would mean that additive genetic variation is very important to the expression of that trait.

However, if the slope was zero, that would mean the heritability is zero and then that means that non-addictive genetic variation or environmental factors are playing an important role in the expression of that trait. So if you’re looking at the bottom left of this line are a bunch of different parent offspring regressions. So. the thin, dark line shows you the parent offspring aggression across the whole experiment, regardless of treatment. The thick, dark line shows the heritability for control flies and we’re interested in here is if you have a mother or grandmother. That are chapter called chapter of their maternal effects program, material effects on the expression of these traits and so called shock is represented here in blue and heat. Shock is represented here and read the solid lines or maternal thermal shocks. And the dash lines represent grand maternal thermal shocks. And so for each of these groups, you can see that there are slope’s that are not similar to the slopes that are observed in the control experiments or the experiment wrong. And so if you look at cold shock, cold, shocking mother’s results in a reduction in the slope of the parent offspring, aggression or reduction heritability, and the cold shocked grandmother results in the elimination of a relationship between parent and offspring development times.

On the Hitchcocks side, the pattern is a little different. There appears to be no relationship between parent and offspring type after maternal heat shock, but grand maternal heat shock seems to result in a deepening of the relationship between paragraphs regression. So at the moment, we’ve evaluated two trials. We’d like to evaluate more before we move for publication on this. But at the moment, it appears as if there are both maternal and gran maternal effects on the development time of the Blowfly Cokely in Miami area, which is a common blowfly in the state of Texas. And these effects appear to differ depending on whether there is a heat shock or cold shock and what generation was thermally stressed.

So maternal effects and are expected. Mothers put proteins and other metabolites in the eggs that they’re producing internally, so it’s not a shock then that if you alter the physiology of a female, she might change your proteins or what other metabolites she gives her offspring. So in this sense, maternal effects are not a surprise. However, the intergenerational epigenetic effects implied by the effect of grand maternal heat and cold shock. Are less expected.

So if flies lack a major mechanism that is observed in many other organisms to result in intergenerational epigenetic effects, and that is the methylation of the genome. So many organisms there are exposed to environments that alter their phenotypes for multiple generations.

There is a methylation of the genome that alters expressions of certain genes until that methylation marker changes. And so flies don’t have methylation genes that even other insects and other families have. So they seem to lack that capability. Yet they still seem capable of exhibiting these intergenerational effects on the genetics of development time. One of the more interesting things to us is whether you’re dealing with blowflies is temporal markers and death investigations or whether you’re thinking about, uh, the impact of blowflies and nutrient recycling. Is that the results from this experiment so far imply some seasonality to blowfly development times and more specifically seasonality to the importance of genetic contributions of parents to their offspring’s phenotype. So. This is an interesting avenue that we’d like to pursue further, we can imagine some basic biology grants pursuing NSF funding, et cetera, and some applied grants, for instance, to the National Institute of Justice to understand the role of this sort of process and the resulting uncertainty in forensic instruments with butterfly data sets.

So, again, and we’d like to thank you for attending our poster, and I appreciate you taking the time to see what we’ve done with our T3 grant.