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Stressed! How do animals cope with what life throws at them?

Dr Amanda Bretman (SoB), Dr Elizabeth Duncan, Dr Steven Sait

Contact email: a.j.bretman@leeds.ac.uk

Summary

Animals face many environmental stresses, and this is only likely to get worse as we face an era of rapid climate change. This brings into sharp focus the need to understand what the responses to stressors are and what molecular mechanisms underpin the strategies animals use to cope with stress. In this way we can better understand what the consequences of environmental stress will be and whether animals will cope on ecological and evolutionary timescales. This project will investigate how stressors interact, whether they are general stress responses that are common across species and whether the epigenome is key to combatting stress.

Stresses can come from many sources, such as temperature, nutrition, toxins, disease and social interactions. These stresses can be variable and unpredictable, acute or long lasting. Their impact on the individual may reduce future lifespan, reproductive output or ability to fight disease. Often though we only do experiments on single stressors at one period during the lifetime and so we don’t know how stressors combine. It could be the different stresses have cumulative effects or alternatively a mild stress may increase resilience to subsequent stress (known as hormeisis). For example, our recent work shows that social contact is differentially stressful for males and females (Leech et al 2017), and this alters their ability to withstand thermal stress and infection (Leech, Sait and Bretman in prep). This shows it is also important to measure sex differences in stress responses.

To combat these stresses individuals can be plastic in their behaviour or physiology, but the mechanisms that underlie these processes are not well understood. The epigenome (marks on the genome that alter gene expression) is environmentally sensitive and so may be a mechanism that allows animals respond to the environment through gene regulation. Changes to the epigenome can be long lasting, so could hold the key to how a current stress alters resilience to future stress. Information about the environment an animal experiences can affect gene expression and the epigenome (Duncan et al., 2014). This enables the epigenome to be environmentally sensitive, for example to maternal nutrition (Dolinoy et al., 2007), heat stress (Seong et al., 2011), amount of parental care (Roth et al., 2009), stressful confinement (Rodgers et al., 2015), and environmental toxins such as cigarette smoke (Qiu et al., 2015). Despite the fact that changes to the epigenome can be fast, occurring within hours (e.g. Kangaspeska et al., 2008), these changes states can have long lasting effects on the individual and even transgenerational effects as epigenetic information can be passed from parent to offspring (e.g. Roth et al., 2009). The epigenome may therefore be key to how individuals cope with acute stress but also whether stresses have longer term consequences.

As yet we have limited understanding of what effect stresses have on the epigenome and hence subsequent fitness of the animal and whether different stresses cause similar responses. To explore this we will use insect model systems (Drosophila fruit flies, Indian meal moths, bees) and interfere with various epigenetic marks chemically and genetically (using transgenic fruit flies). We will test whether there are commonalities in responses across different stressors (hot and cold temperatures, starvation, desiccation, crowding) and how these stressors interact. By using various insect species we can test the generality of responses. To examine how stresses alter epigenetic states, we will employ cutting edge sequencing technology (ChIP-seq). In an increasingly changing world, this will give us exciting new insights into how animals cope with environmental stress and how the epigenome interacts with fitness.

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References

Dolinoy et al 2007 PNAS 104, 13056

Duncan et al 2014 J. Experimental Zool B 322, 208

Kangaspeska et al 2008 Nature 452, 112

Leech et al 2017 J. Insect Phys 

Qiu et al 2015 Epigenetics 10, 1064

Rodgers et al 2015 PNAS 112, 13699

Roth et al 2009 Biol. Psychiatry 65, 760

Seong et al 2011 Cell 145, 1049

Related undergraduate subjects:

  • Biology
  • Ecology
  • Evolution
  • Zoology