THE GENETICS AND EVOLUTION OF MATERNAL EFFECTS ON PARASITE RESISTANCE

Different mothers will have different experiences. Some mothers will be able to eat more, or higher quality food. This will not only affect them, but also their offspring in how likely they are to contract an infectious disease or parasite. This is true for most organisms, including humans.

For example, some animals simply make bigger eggs under certain conditions. In many animals this is when they have more food, but the less intuitive scenario can also occurs: some animals make larger eggs when there is less food. Either way, the bigger offspring from these eggs are more resistant to parasites. Such a strategy, where mothers prepare offspring for what they predict as tough times ahead, are called maternal effects. These are traits passed down to offspring that are not coded in their genes. However, independent of these maternal effects, a mother will also pass genes to her offspring. So, offspring may be resistant simply because their mother was resistant and they inherited her genes. Thus, there are two reasons an offspring could be resistant: maternal effects and genes (or a combination of both). We want to understand how these two effects work together to make offspring either susceptible or resistant to being infected by parasites, and we want to understand how populations might change (evolve) in this regard. The sort of fundamental experiments required would be very difficult to do in a human or a mouse, and so we have designed experiments with a small, rapidly-evolving crustacean, Daphnia. This crustacean is easy to work with in the laboratory, but is also found all over the world in small ponds and lakes. Therefore, any experiments done in the laboratory can inform us about what is happening in nature.

Our experiments will:

1) illustrate how maternal conditions (say, more or less food) affect how resistant their offspring are to infection
2) determine if these maternal effects are costly and for example, whether or not they accelerate the aging process
3) study how maternal effects differ depending on the genes of the mother
4) determine how maternal effects evolve in nature as a consequence of parasite epidemics

Although elements of the proposed research are curiosity-driven, knowledge-transfer between such basic research and more applied realms is essential. In particular, this knowledge can help us to identify, and even predict, the conditions under which disease outbreaks may occur. In turn, end-users and policy-makers can develop the capacity to contain or avert outbreaks of diseases, either in humans, or as part of the effort to conserve vulnerable animal populations.

IMPACT SUMMARY

Our proposed work links traditional life-history studies, multi-generational experiments, studies of parasitic disease in the field and molecular studies of immune responses. As such, we see broad sections of the academic community potentially benefitting from our research. These include disease biologists, evolutionary biologists, epidemiologists and parasitologists. Knowledge-transfer between basic research, such as ours, and more applied realms is essential for the development of predictive epidemiological models. This in turn is essential for end-users and policy makers to develop the capacity to understand, contain or avert outbreaks of diseases.

Outside traditional academic communities, we envision that the following groups might benefit from the research we propose:

1) Fisheries conservation. Maternal effects are increasingly recognised as an important factor for stock abundance, and parasites have been found to contribute significantly to fish population declines. Yet, maternal effects on disease resistance have not yet been incorporated into this line of thought.

2) Pollinator conservation. The decline of pollinators is a worldwide concern with substantial economic importance. The rapid transfer of parasites is a major hypothesis to explain the problem, but the role that maternal condition plays in, for example, honey bee health, is not well-studied.

3) Vectors of disease. The maternal conditions that mosquitoes experience are already established to effect blood meal sizes in offspring and the probability of vectoring parasites, but we believe there is scope to further these types of experiments, particularly now with genetically-modified vectors being actively released into the wild

4) Senescence and aging. Calorie restriction is now established to play a role in senescence and aging, and we see merit in considering how maternal effects impact immune responses and indirectly, senescence (indeed this is a major goal of our proposed work).

How might these fields benefit from the propose Research?

All of the above four areas have major effects upon UK health and wealth, and it is our aim that the study of maternal effects shall enhance this by modifying practice in each area.

Timescales

As the work we are conducting is basic science, the timescales for these benefits to be felt by the UK are difficult to predict and probably long term. Nevertheless, we feel that productive contact with the above fields could be initiated within the timeframe of this grant via:

Two one-day symposia to help to maximize the impact of the ideas contained in the proposal

In an effort to maximize benefits and speed up the delivery of positive effects (and the help give our research high profile exposure wherever possible) we propose a set of conferences with a focus on maternal effects on immunity, disease and aging. The first of these will be more academic, and designed to synthesize the scientific area of the current proposal, while the second symposia will then take this synthesis forward and deliver it to the applied fields mentioned above. As such, we intend to invite key speakers from the realm of pollinator conservation, fisheries management, genetically-modified vectors and the evolution of "aging" field. The model for both symposia shall be similar to symposia TL and colleagues have organised for the Wellcome Trust-funded Center for Immunity Infection and Evolution (CIIE), based at the Ashworth Laboratories, University of Edinburgh. See, for example, http://ciie.bio.ed.ac.uk/node/296. We have requested specific funds to enable these outreach symposia.