Major evolutionary transitions to obligate symbioses

Theme: Evolution & Adaptation

Primary Supervisor:

Lee Henry

School of Biological and Behavioural Sciences, QMUL

Lee Henry's Profile Picture

Secondary Supervisor:

Chema Martin-Duran

School of Biological and Chemical Sciences, QMUL

Chema Martin-Duran's Profile Picture

Project Description:

Over time, host and symbiont can become so tightly associated that they combine to form a new, more complex life form. This type of extreme symbiotic dependence has resulted in some of the most important evolutionary transitions including the origins of the eukaryotic cell, mitochondria and chloroplast. However, we currently know little about what promotes the stability of these relationships, and how hosts and symbionts integrate over time at a molecular and cellular level.

In this project, the student will investigate the metabolic, genomic and cellular changes that occur as a host and symbiont integrate into a new higher-level organism. Invertebrates offer unique insight into the development of these relationships as they have repeatedly evolved obligate dependence on endosymbionts. Our results suggest that the integration of a new symbiont proceeds in a predictable manner – through parallel evolutionary processes (Monnin et al 2020). We now aim to gain a mechanistic and functional understanding of the initial changes that occur when hosts evolve dependence on a microbe, to the advanced integration of an ancient obligate symbiont.

To achieve this aim, we are comparing diverse lineages of annelids, ants and aphids that have evolved obligate and co-obligate symbioses. Key questions the student may investigate include:

1. What are the step-wise transcriptional and cellular changes that occur as host and symbiont integrate over evolutionary
2. What initial gene losses bind host and symbionts into dependence?
3. What are the genetic mechanisms involved in host control over symbionts?

*Students are encourage to develop their own ideas

Policy Impact of Research:

Obligate symbioses are globally important for ecosystem functioning through their central role in nutrient cycling and energy conversion (e.g. corals, choroplasts). This project will provide fundamental information on how eukaryotes form and maintain these permanent relationships with microbes.

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