DNA remodelling by Strict Partial Endoreplication in orchids, an original process in the plant kingdom

Spencer C. Brown (1, 2, 3, 4, 5) , Mickaël Bourge (1, 6) , Nicolas Maunoury (7) , Maurice Wong , Michele Wolfe Bianchi (1, 2, 3, 5, 8, 9) , Sandra Lepers-Andrzejewski , Pascale Besse (10) , Sonja Siljak-Yakovlev (11) , Michel Dron (12, 5) , Béatrice Satiat-Jeunemaître (7, 1, 13, 14, 15)

1 I2BC - Institut de Biologie Intégrative de la Cellule
2 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
3 CNRS - Centre National de la Recherche Scientifique
4 Université Paris Sud (Paris 11)
5 Université Paris-Saclay
6 Plateforme intégrée IMAGIF
7 ISV - Institut des sciences du végétal
8 Unite de Formation et de Recherche Sciences et Technologie
9 UPEC UP12 - Université Paris-Est Créteil Val-de-Marne - Paris 12
10 UMR PVBMT - Peuplements végétaux et bioagresseurs en milieu tropical
11 Laboratory for Research and Protection of Endemic Resources
12 VIM (UR 0892) - Virologie et Immunologie Moléculaires
13 BioCell - Département Biologie Cellulaire
14 DYNBSJ - Dynamique de la Compartimentation cellulaire dans les cellules de plantes supérieures
15 CYTO - Cytométrie

DNA remodelling during endoreplication appears to be a strong developmental characteristic in orchids. In this study, we analysed DNA content and nuclei in 41 species of orchids to further map the genome evolution in this plant family. We demonstrate that the DNA remodelling 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 to 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 hybridisation 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.

Mots clés: Genome Size; Vanilla; PF; BIOCELL; CYTO; DYNBSJ; MINION; IMAGIF; PHOT; cytogenetics; cytometry; endoreplication; genome imbalance

Domaines: Sciences du Vivant [q-bio]

Spencer C. Brown, Mickaël Bourge, Nicolas Maunoury, Maurice Wong, Michele Wolfe Bianchi, et al.. DNA remodelling by Strict Partial Endoreplication in orchids, an original process in the plant kingdom. Genome Biology and Evolution, 2017, 9 (4), pp.1051-1071. ⟨10.1093/gbe/evx063⟩. ⟨hal-02187753⟩