Vabiome (Reunion, Paris and French Polynesia teams) has published in Genome Bio. Evol. "DNA Remodeling by Strict Partial Endoreplication in Orchids, an Original Process in the Plant Kingdom" by Spencer C. Brown, Mickaël Bourge, Nicolas Maunoury, Maurice Wong, Michele Wolfe Bianchi, Sandra Lepers-Andrzejewski, Pascale Besse, Sonja Siljak-Yakovlev, Michel Dron and Béatrice Satiat-Jeunemaître.
DNA remodeling during endoreplication appears to be a strong
developmental characteristic in orchids. In this study, we analyzed DNA
content and nuclei in 41 species of orchids to further map the genome
evolution in this plant family. We demonstrate that the DNA remodeling
observed in 36 out of 41 orchids studied corresponds to strict partial
endoreplication. Such process is developmentally regulated in
each wild species studied. Cytometry data analyses allowed us to propose
a model where nuclear states 2C, 4E, 8E, etc. form a series comprising a
fixed proportion, the euploid genome 2C, plus 2–32 additional copies of
a complementary part of the genome. The fixed proportion ranged from
89% of the genome in Vanilla mexicana down to 19% in V. pompona,
the lowest value for all 148 orchids reported. Insterspecific
hybridization did not suppress this phenomenon. Interestingly, this
process was not observed in mass-produced epiphytes. Nucleolar volumes
grow with the number of endocopies present, coherent with high
transcription activity in endoreplicated nuclei. Our analyses suggest
species-specific chromatin rearrangement. Towards understanding
endoreplication, V. planifolia constitutes a tractable system
for isolating the genomic sequences that confer an advantage via
endoreplication from those that apparently suffice at diploid level.
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