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Diploid-dominant life cycles characterize the early evolution of Fungi

Summary

Scientists studied the evolutionary history of fungi by sequencing the genomes of 69 water-dwelling fungi. They discovered that contrary to what textbooks say, many fungi actually have diploid-dominant life cycles (like animals) rather than haploid-dominant ones (with single copies of genes). The ancient ancestor of all fungi was likely diploid, and different fungal groups lost this trait at different times in evolution.

Background

Fungi have traditionally been characterized as having haploid-dominant (haplontic) life cycles, but this understanding is primarily based on the Dikarya subkingdom, which contains most described fungal species. Early-diverging fungal lineages, particularly zoosporic fungi, remain poorly understood despite representing significant phylogenetic diversity.

Objective

To establish a comprehensive phylogeny of early-diverging fungal lineages and reassess the evolution of life cycles and cellular characters using genomic data from 69 newly sequenced zoosporic fungi.

Results

Phylogenomic analyses revealed a robustly supported paraphyletic arrangement of five zoosporic fungal lineages. Heterozygosity analysis showed that diploid-dominant life cycles are common across most early-diverging fungal lineages, contrary to the traditional haplontic characterization. Ancestral state reconstruction indicated a 59% likelihood that the most recent common ancestor of all fungi was diploid.

Conclusion

Many fungal lineages have diploid-dominant life cycles, indicating that haplontic life cycles characteristic of some major groups are likely derived rather than ancestral. Early-diverging fungi retained ancestral traits shared with Metazoa that have been lost in derived lineages, indicating gradual transition in fungal genetics and cell biology from their protist-like ancestor.
  • Published in:Proceedings of the National Academy of Sciences of the United States of America,
  • Study Type:Phylogenomic analysis,
  • Source: PMID: 36037379, DOI: 10.1073/pnas.2116841119
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