Radical cell identity bifurcation in Saccharina embryos coincides with the expression of newly acquired genes
Abstract
Brown algae evolved independently from animals, land plants and other algae, and we know very little about the spatio-temporal dynamics of their embryogenesis. Here, we used time-lapse, bright-field microscopy to study cell division and lineage development during early embryogenesis in the kelp Saccharina latissima , a large brown alga. We discovered a radical change of cell identity as early as the 4-cell stage: after fertilization, the zygote underwent two or three unequal cell divisions before the basal cell – that closest to the maternal tissue – stopped dividing and radically differentiated into a hyperpolarized cell, the rhizoid, which anchors the embryo to the substrate. RNA-seq analysis showed that differentiation of rhizoid cells was preceded by expression of 130 basal cell-specific genes. Phylostratigraphic analysis further revealed that more than 40% of these basal cell-specific genes appeared after the emergence of the brown algae group, and their functions are largely unknown. By contrast, the apical cell predominantly expressed more ancestral, metabolism-related genes, and it continued to divide to produce the long, blade-shaped thallus of the alga. The early and radical nature of cell differentiation in Saccharina embryos, combined with differential gene expression from various evolutionary periods, highlights the unique mechanisms of embryogenesis of this alga.
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BibTeX
@misc{theodorou2026radical,
title = {{Radical cell identity bifurcation in Saccharina embryos coincides with the expression of newly acquired genes}},
author = {Ioannis Theodorou and Olivier Godfroy and Samuel Boscq and Bernard Billoud and Yves Dusabyinema and Bénédicte Charrier},
howpublished = {HAL},
year = {2026},
month = may,
doi = {10.64898/2026.05.13.724814},
url = {https://hal.science/hal-05791768v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Radical cell identity bifurcation in Saccharina embryos coincides with the expression of newly acquired genes
AU - Ioannis Theodorou
AU - Olivier Godfroy
AU - Samuel Boscq
AU - Bernard Billoud
AU - Yves Dusabyinema
AU - Bénédicte Charrier
PY - 2026
DA - 2026/05/16
PB - HAL
DO - 10.64898/2026.05.13.724814
UR - https://hal.science/hal-05791768v1
AB - Brown algae evolved independently from animals, land plants and other algae, and we know very little about the spatio-temporal dynamics of their embryogenesis. Here, we used time-lapse, bright-field microscopy to study cell division and lineage development during early embryogenesis in the kelp Saccharina latissima , a large brown alga. We discovered a radical change of cell identity as early as the 4-cell stage: after fertilization, the zygote underwent two or three unequal cell divisions before the basal cell – that closest to the maternal tissue – stopped dividing and radically differentiated into a hyperpolarized cell, the rhizoid, which anchors the embryo to the substrate. RNA-seq analysis showed that differentiation of rhizoid cells was preceded by expression of 130 basal cell-specific genes. Phylostratigraphic analysis further revealed that more than 40% of these basal cell-specific genes appeared after the emergence of the brown algae group, and their functions are largely unknown. By contrast, the apical cell predominantly expressed more ancestral, metabolism-related genes, and it continued to divide to produce the long, blade-shaped thallus of the alga. The early and radical nature of cell differentiation in Saccharina embryos, combined with differential gene expression from various evolutionary periods, highlights the unique mechanisms of embryogenesis of this alga.
ER -