Trávníček, P., Ponert, J., Urfus, T., Jersáková, J., Vrána, J., Hřibová, E., Doležel, J., Suda, J.
CYTOMETRY
87A:
958-966,
2015
Keywords:
C-value; endopolyploidy; flow cytometry; genome size; histogram interpretation; nuclear DNA content; orchid; progressively partial endoreplication
Abstract:
Nuclear genome size is an inherited quantitative trait of eukaryotic organisms with
both practical and biological consequences. A detailed analysis of major families is a
promising approach to fully understand the biological meaning of the extensive variation
in genome size in plants. Although Orchidaceae accounts for 10% of the angiosperm
diversity, the knowledge of patterns and dynamics of their genome size is
limited, in part due to difficulties in flow cytometric analyses. Cells in various somatic
tissues of orchids undergo extensive endoreplication, either whole-genome or partial,
and the G1-phase nuclei with 2C DNA amounts may be lacking, resulting in overestimated
genome size values. Interpretation of DNA content histograms is particularly
challenging in species with progressively partial endoreplication, in which the ratios
between the positions of two neighboring DNA peaks are lower than two. In order to
assess distributions of nuclear DNA amounts and identify tissue suitable for reliable
estimation of nuclear DNA content, we analyzed six different tissue types in 48 orchid
species belonging to all recognized subfamilies. Although traditionally used leaves may
provide incorrect C-values, particularly in species with progressively partial endoreplication,
young ovaries and pollinaria consistently yield 2C and 1C peaks of their G1-
phase nuclei, respectively, and are, therefore, the most suitable parts for genome size
studies in orchids. We also provide new DNA C-values for 22 orchid genera and 42 species.
Adhering to the proposed methodology would allow for reliable genome size estimates
in this largest plant family. Although our research was limited to orchids, the
need to find a suitable tissue with dominant 2C peak of G1-phase nuclei applies to all
endopolyploid species.
Fulltext: contact IEB authors
IEB authors: Jaroslav Doležel,
Eva Hřibová,
Jan Vrána