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Selection on proteins during the transition to multicellularity - A study on volvocine algae

Ramnath, Vignesh (2019) BINP51 20181
Degree Projects in Bioinformatics
Popular Abstract
Selection on proteins during the transition to multicellularity

The evolution of unicellular organisms into more complex, multicellular groups has been one of the most important transitions in life. One way of studying the molecular mechanisms involved in this transition is to quantify changes in proteins that have functions proposed to be important in the formation and coordination of multicellular groups.

In my research, I work with volvocine green algae (Fig 1), which provide a perfect model system for studying this transition for two key reasons. First, members of this group range in complexity from simple unicellular to complex multicellular species of varying shape and size. Secondly, the species in this group are relatively... (More)
Selection on proteins during the transition to multicellularity

The evolution of unicellular organisms into more complex, multicellular groups has been one of the most important transitions in life. One way of studying the molecular mechanisms involved in this transition is to quantify changes in proteins that have functions proposed to be important in the formation and coordination of multicellular groups.

In my research, I work with volvocine green algae (Fig 1), which provide a perfect model system for studying this transition for two key reasons. First, members of this group range in complexity from simple unicellular to complex multicellular species of varying shape and size. Secondly, the species in this group are relatively young (~230 MY). I developed a computational pipeline (Fig 2) to identify lineages where proteins have evolved, pinpoint which amino acids have changed, and examine if this is linked to transitions to multicellularity.

My research indicated that all three candidate proteins were under strong purifying selection and were relatively conserved across the volvocine phylogeny, with no lineages showing evidence of positive selection. However, I found specific amino acids have evolved under positive selection in certain lineages of the volvocine algae and observed a clear pattern between the number of positively selected sites and level of multicellular complexity. Most of the sites were found in multicellular organisms with undifferentiated germ-soma (Fig 1a- Red font) in all three proteins, with very few or a complete lack of such sites in unicellular and multicellular organisms with a partial or complete separation of germ and soma. Using the sites detected under selection in multicellular undifferentiated lineages, we can guide follow-up work on the protein structure and function of these sites highlighted to be important in the maintenance of multicellularity and understanding the genetic changes involved in early stages in this transition. The pipeline I developed is flexible and efficient and can be extended to test patterns of selection and study gene evolution across the tree of life.

Master’s Degree Project in Bioinformatics, 45 credits, 2019
Department of Biology, Lund University

Advisor: Charlie Cornwallis
Co-advisor: Maria Svensson Coelho

Section of Molecular Ecology and Evolution, Department of Biology (Less)
Please use this url to cite or link to this publication:
author
Ramnath, Vignesh
supervisor
organization
course
BINP51 20181
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8975167
date added to LUP
2019-05-08 09:51:03
date last changed
2019-05-08 09:51:03
@misc{8975167,
  author       = {{Ramnath, Vignesh}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Selection on proteins during the transition to multicellularity - A study on volvocine algae}},
  year         = {{2019}},
}