Journal Article

A “Developmental Hourglass” in Fungi

Xuanjin Cheng, Jerome Ho Lam Hui, Yung Yung Lee, Patrick Tik Wan Law and Hoi Shan Kwan

in Molecular Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 32, issue 6, pages 1556-1566
Published in print June 2015 | ISSN: 0737-4038
Published online March 2015 | e-ISSN: 1537-1719 | DOI:
A “Developmental Hourglass” in Fungi

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  • Evolutionary Biology
  • Molecular and Cell Biology


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The “developmental hourglass” concept suggests that intermediate developmental stages are most resistant to evolutionary changes and that differences between species arise through divergence later in development. This high conservation during middevelopment is illustrated by the “waist” of the hourglass and it represents a low probability of evolutionary change. Earlier molecular surveys both on animals and on plants have shown that the genes expressed at the waist stage are more ancient and more conserved in their expression. The existence of such a developmental hourglass has not been explored in fungi, another eukaryotic kingdom. In this study, we generated a series of transcriptomic data covering the entire lifecycle of a model mushroom-forming fungus, Coprinopsis cinerea, and we observed a molecular hourglass over its development. The “young fruiting body” is the stage that expresses the evolutionarily oldest (lowest transcriptome age index) transcriptome and gives the strongest signal of purifying selection (lowest transcriptome divergence index). We also demonstrated that all three kingdoms—animals, plants, and fungi—display high expression levels of genes in “information storage and processing” at the waist stages, whereas the genes in “metabolism” become more highly expressed later. Besides, the three kingdoms all show underrepresented “signal transduction mechanisms” at the waist stages. The synchronic existence of a molecular “hourglass” across the three kingdoms reveals a mutual strategy for eukaryotes to incorporate evolutionary innovations.

Keywords: “developmental hourglass”; transcriptomics; mushroom-forming fungus; Coprinopsis

Journal Article.  6303 words.  Illustrated.

Subjects: Evolutionary Biology ; Molecular and Cell Biology

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