Variability of chromosome structure in pathogenic fungi--of 'ends and odds'

Area of Science:

• * Mycology
• * Epigenetics
• * Molecular Biology

Background:

• * Chromatin structure influences chromosome organization and maintenance.
• * Filamentous fungi exhibit gene clustering for secondary metabolites and pathogenicity islands.
• * Fungal accessory chromosomes, termed 'supernumerary', 'conditionally dispensable', or 'B chromosomes', often confer adaptive traits.

Purpose of the Study:

• * To propose reconsidering the term "supernumerary chromosomes" for fungal accessory chromosomes.
• * To explore potential shared evolutionary mechanisms between fungal accessory chromosomes and animal/plant B chromosomes.
• * To investigate the role of histone modification H3K27me3 in fungal accessory chromosomes.

Main Methods:

• * Comparative analysis of fungal chromosome structures.
• * Investigation of epigenetic modifications, specifically H3 lysine 27 trimethylation (H3K27me3).
• * Examination of gene organization within fungal accessory chromosomes.

Main Results:

• * Fungal supernumerary chromosomes may arise through mechanisms similar to animal and plant B chromosomes.
• * Both chromosome ends and fungal B chromosomes are enriched with the silencing histone modification H3K27me3.
• * This suggests parallel epigenetic regulation in accessory chromosomes and gene clusters.

Conclusions:

• * The term "supernumerary chromosome" should be reconsidered to encompass the diversity of fungal accessory chromosomes.
• * Epigenetic silencing via H3K27me3 may play a crucial role in the regulation of fungal accessory chromosomes and associated gene clusters.
• * Shared evolutionary and regulatory mechanisms may exist between fungal accessory chromosomes and B chromosomes in other eukaryotes.