Some observations on the structure, cation content and possible evolutionary status of dinoflagellate chromosomes

Abstract

SICEE, D. C., 1984. Some observations on the structure, cation content and possible evolutionary status of dinoflagellate chromosomes. Dinoflagellate chromosomes have a well‐ordered structure, as observed in living cells, glutaraldehyde/osmium tetroxide‐fixed cells, ultrathin cryosections and freeze‐etch preparations. It is suggested that the stabilization of this chromatin in the living cell is largely mediated by divalent cations, acting as bridging molecules between the DNA superstructure and the protein matrix. Studies using X‐ray micro‐analysis and autoradiography have shown that these chromosomes have high levels of bound Ca and transition metals, and that these are associated with both the DNA and surrounding proteins. The organization and stabilization of chromatin in dinoflagellate chromosomes is quite different from that of the cells of other eukaryotes, but shows some resemblance to the dispersed chromatin of bacteria. The evolution of dinoflagellate chromosomes from a prokaryote‐like ancestral genome is attributed to two main factors–the retention of a primitive cationic non‐histone stabilization system, and a pronounced evolutionary trend towards high DNA values. On this theory, dinoflagellate chromosomes are phylogenetically distinct from all other eukaryote chromosomes, and provide a separate evolutionary route for the attainment of high DNA levels and increased cell size.

Aspects of iron and nitrogen nutrition in the red tide dinoflagellateGymnodinium sanguineum

“…Iron occurring as a component of dinoflagellate chromatin (Sigee 1984) represents at least one non-catalytic iron requirement unique among other algae and higher Doucette and P.J. Harrison: Dinoflagellate Fe and N nutrition.…”

Targeted volume correlative light and electron microscopy of an environmental marine microorganism

“…As the properties of these threads are very similar to the chromosomes they are originating from, we believe that they represent a chromatin intermediate unfolding state. Previous studies suggested that DNA structures protruding from the chromosome core have a role in RNA transcription ( Rizzo, 1991 ; Sigee, 1983 , 1984 ; Soyer-Gobillard et al, 1990 ). Such structures, originating from the chromosomes and branching towards the nucleoplasm, have been reported in various dinoflagellate species ( Bhaud et al, 2000 ; Decelle et al, 2021 ; Soyer-Gobillard et al, 1990 ).…”

Organization of the genome and gene expression in a nuclear environment lacking histones and nucleosomes: the amazing dinoflagellates

“…1A and B), with a maximum unwinding corresponding with the peak of replication in S phase (Spector et al, 1981;Costas and Goyanes, 2005). They are attached to the nuclear envelope and have a unique organization (Sigee, 1984a;Dodge, 1985;Rizzo, 1991). Free-living dinoflagellates have high chromosome numbers per haploid genome (20-270) (compare Fig.…”