A heritable structural alteration of the yeast mitochondrion

Area of Science:

• Cell Biology
• Genetics
• Yeast Biology

Background:

• Prions have renewed interest in non-genetic hereditary changes.
• Understanding structural inheritance mechanisms is crucial.
• The mitochondrion is a key organelle in cellular structure and function.

Purpose of the Study:

• To characterize a novel heritable structural change in Saccharomyces cerevisiae mitochondria, termed [Leu(P)].
• To investigate the mechanisms and phenotypes associated with [Leu(P)].
• To determine if [Leu(P)] represents a prion or a new class of structural inheritance.

Main Methods:

• Phenotypic analysis of [Leu(P)] and [Leu(+)] yeast strains.
• Growth rate measurements under different conditions (e.g., absence of leucine).
• Mitochondrial inheritance studies using cytoduction and assessment of protein localization.

Main Results:

• [Leu(P)] strains exhibit twofold slower growth and threefold slower growth without leucine.
• [Leu(P)] is associated with delocalization of nuclear-encoded mitochondrial proteins.
• Cytoduction experiments demonstrated inter-mitochondrial transfer of the [Leu(P)] trait.
• Evidence suggests non-Mendelian inheritance and incomplete dominance.

Conclusions:

• [Leu(P)] represents a heritable structural change in yeast mitochondria, often linked to mitochondrial genome alterations.
• The trait's characteristics, including incomplete dominance and lack of response to HSP104 deletion, differentiate it from prions.
• [Leu(P)] may represent a novel class of structural inheritance in eukaryotes.