STAR: Kin recognition and the transition to aggregative multicellularity

The evolution of multicellularity from unicellular ancestors fundamentally altered the history of life, giving rise to an astounding diversity of complex organisms. While scientists have made significant progress understanding this transition in organisms that develop through cell division (like most plants and animals), a major question remains: how does multicellularity evolve in organisms that form groups by cells coming together and sticking to each other - a process called aggregation?

Aggregative systems face a fundamental constraint: multicellular organisms can be comprised of unrelated cells, so natural selection is more likely to act on the traits of cells than the traits of the collective as a whole. Using yeast as a model system, this research investigates whether the ability to recognize and preferentially stick to genetically related cells (kin recognition) was crucial for the evolution of aggregative multicellularity.

This project will provide unique insights into the origins of increasingly complex life and contribute to our understanding of the processes driving major evolutionary transitions. Additionally, this project will support broadening participation in STEM through mentorship of a female postdoctoral researcher from a low-income background, and will provide research experiences for undergraduate women.

This project will test the hypothesis that kin recognition enables the evolution of multicellular adaptations by increasing the covariance between collective-level traits and the underlying genotype. The researchers will test this hypothesis using experimentally evolved strains of flocculating yeast, Saccharomyces cerevisiae, that have developed the ability to recognize and preferentially bind to related cells.

Aim 1 will identify the molecular mechanisms of kin recognition through genetic engineering and competition experiments examining whether changes in the FLO1 binding protein alone or coordinated changes between FLO1 and other cell wall components underlie preferential aggregation with clonemates. In Aim 2, the researchers will assess how specific this recognition system is by testing whether independently evolved strains can distinguish between different genetic lineages.

Confocal microscopy will be used to analyze the three-dimensional arrangement of cells within groups to determine if cells specifically recognize and bind to relatives at the cellular level. The results will provide mechanistic insights into how micro-scale interactions between cells underpin the origin of assortment at the level of multicellular groups, advancing our understanding of how genetically-diverse cellular aggregates make the transition to multicellularity.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.