Genetic switch between unicellularity and multicellularity in marine yeasts

Area of Science:

• Evolutionary Biology
• Mycology
• Genetics

Background:

• The transition from unicellular to multicellular life is a major evolutionary event.
• Facultative clonal multicellularity, where organisms can switch between unicellular and multicellular states, may represent an intermediate evolutionary stage.
• The underlying genetic and cellular mechanisms controlling this switch are largely unknown.

Purpose of the Study:

• To identify the genetic and cellular basis of nutrition-responsive facultative clonal multicellularity in black yeasts.
• To understand the molecular mechanisms regulating transitions between unicellular and multicellular growth.
• To explore the ecological factors influencing facultative multicellularity.

Main Methods:

• Genetic analysis of gene deletions in Hortaea werneckii to observe phenotypic changes.
• Identification of key regulatory genes, including a Myb protein, involved in state transitions.
• Ecological studies involving sponge-associated yeasts and the effect of sponge-conditioned medium.

Main Results:

• Deletion of ten specific genes in H. werneckii resulted in stable unicellular or multicellular phenotypes.
• Six of these genes are regulators of conidiation in filamentous fungi, suggesting co-option for multicellularity.
• A Myb protein acts as a switch, with its expression and degradation tied to nutrient availability, controlling unicellular/multicellular states.
• The Myb gene is not essential for facultative multicellularity in the related species Neodothiora pruni.
• Multicellularity in H. werneckii is induced by sponge-associated environments.

Conclusions:

• This study establishes a model system for studying facultative clonal multicellularity.
• Identified genetic and cellular strategies for gaining, losing, and regaining multicellularity.
• Highlights the molecular diversity in regulating phenotypic plasticity across species.