Alternative splicing and subfunctionalization generates functional diversity in fungal proteomes

Area of Science:

• Molecular Biology
• Mycology
• Genetics

Background:

• Alternative splicing is a common mechanism for proteome diversification in Metazoa, but is rare in fungi.
• The SKI7/HBS1 gene is an ancient, alternatively spliced gene found in many fungal species, producing two distinct proteins.

Purpose of the Study:

• To investigate the evolutionary history and functional consequences of alternative splicing in fungal genes.
• To explore the mechanisms of gene duplication and subfunctionalization in fungi, particularly concerning the SKI7/HBS1 gene.

Main Methods:

• Comparative genomics analysis of SKI7/HBS1 gene across fungal lineages.
• Functional characterization of proteins expressed from single-gene loci in yeast models.
• Analysis of gene duplication events and subsequent loss of alternative splicing.

Main Results:

• The ancestral SKI7/HBS1 gene produces two functionally distinct proteins in Lachancea kluyveri, demonstrating subfunctionalization.
• Saccharomyces cerevisiae lost alternative splicing after whole-genome duplication, resulting in separate HBS1 and SKI7 genes.
• Loss of alternative splicing coupled with gene duplication is a recurring mechanism for preserving gene function in fungi, as seen with PTC7 genes.

Conclusions:

• The study reveals a novel mechanism of subfunctionalization in fungi involving the loss of alternative splicing after gene duplication.
• This ancient alternative splicing event and its subsequent loss provide insights into fungal genome evolution and proteome diversification.
• The findings highlight the plasticity of gene regulation and function in fungi, offering a contrast to metazoan strategies.