The Phylotranscriptomic Hourglass Pattern in Fungi: An Updated Model

The “developmental hourglass” describes the morphological convergence to a conserved form at mid-stages of animal embryogenesis. The molecular hourglass pattern during embryogenesis was also identified across kingdoms. Previously, we reported young fruiting body as the conserved “waist” in mushroom-forming “developmental hourglass”. However, its robustness is doubted because of the fungal diversity. Additionally, fungi lack embryogenesis, and develop directly from spore to hyphae with morphological similarities during the transition. Here, we updated the “developmental hourglass” model in the life cycle of fungi, namely, spore germination, vegetative growth, and sexual reproduction. Germinating spores, both sexual and asexual, showed the strongest transcriptomic conservation signals across the phyla Mucoromycota, Ascomycota and Basidiomycota. Cross kingdom comparisons revealed high expression levels of “information storage and processing” genes at the waist stages of embryonic and non-embryonic developments in animals, plants, and fungi. The “developmental hourglass” might reflect the mutual transcriptome switches on developmental transitions in eukaryotes that are additional to embryonic organogenesis. Highlights Updated fungal molecular “developmental hourglass” model in the life cycle of fungi Germinating spores are the evolutionarily conserved “waist” across fungal phyla High expression levels of “information storage and processing” genes at the waist stages in the embryonic and non-embryonic hourglasses across kingdoms “Developmental hourglass” may reflect the mutual transcriptome switches on developmental transitions in eukaryotes