Estimates of Nuclear DNA Content in Bryophyte Sperm Cells: Phylogenetic Considerations

Abstract

Nuclear DNA contents of developing sperm were estimated for 17 species of bryophytes by cytophotometry in squash preparations of antheridia after Feulgen staining. Genome sizes are in the lower end of the range for land plants. Two hornwort C-values have the lowest recorded for bryophytes at 0.17 and 0.26 pg DNA per nucleus. In liverworts, C-values range from 0.49 pg in Blasia pusilla to 4.05 pg in Pel/ia epiphylla, while moss genome sizes are less variable, ranging from 0.38 pg in Takakia ceratophylla to 0.92 pg in Atrichum oerstedianum. DNA content is not correlated with chromosome number in these bryophytes, but sperm cell size and cellular complexity are directly related to C-value. Structural variations in the locomotory apparatus are viewed as evolutionary modifications associated with changes in genomic complexity, with a generalized increase in complexity ofthe motile assemblage accompanying increases in DNA content. Nuclear DNA values are not as variable in bryophytes as they are in pteridophytes and seed plants. We suggest that in plants producing biflagellated gametes, lower DNA contents afford a selective advantage. Comparisons with plants that produce multiflagellated or pollendispersed sperm indicate operation of a nucleotypic effect in archegoniates with biflagellated sperm. This effect may be on sperm cell functioning, which in tum influences reproductive success.

Nuclear differentiation in the filamentous caulonema of the moss Funaria hygrometrica

“…Since these nuclei are not from dividing cell types, they are probably nuclei with a IC DNA complement. This figure of 0-5 pg for Funaria is closely in line with the (Renzaglia et al, 1995), From cell 4, there are successive rounds of DNA synthesis, the DNA complement increases to on average 6C by cell 10, Knoop (1978) reported that endoreduplication in F. hygrometrica can occur to 16C. The rate of DNA synthesis causing the endoreduplication of the genome in cells +-10 is similar to the rate of DNA synthesis that occurs in the apical cell (Fig.…”

“…Kreitner & Reighard, 1968; angiosperms (Tri/icwm flcsfiruw L.). antipodal nuclei Duckett & Carothers, 1979;Renzaglia, Rasch & Pike, 1995). These nuclear variations can bê To whom correspondence should be addressed.…”

Hornwort Stomata: Architecture and Fate Shared with 400-Million-Year-Old Fossil Plants without Leaves

“…The large size of hornwort stomata is shared with the earliest fossil stomata and is counter to the documented correlation between guard cell length and genome size (Beaulieu et al, 2008;Hodgson et al, 2010). Hornwort genomes are among the smallest of all land plants (Renzaglia et al, 1995). Lomax et al (2014) noted the inconsistency in guard cell length of fossil stomata visa-vis a predicted increase in genome size from the earliest plants through geologic time.…”

Genome sizes of cyclopoid copepods (Crustacea): evidence of evolutionary constraint

“…The operation of such selection factors would favour a smaller genome with shorter replication times for the exploitation of available resources in patchy, often ephemeral and changing environments. Although the relationship is likely to more complex than simple association, the predominance of very small genome sizes found in nature for many freshwater cyclopoids is reminiscent of the small genome sizes reported for many species of bryophytes (Renzaglia, Rasch & Pike, 1995; Voglmayr, 2000). The latter also occur in discontinous and stressful habitats subject to prolonged periods of desiccation.…”

“…The latter also occur in discontinous and stressful habitats subject to prolonged periods of desiccation. Both life forms may be subject to similar selection pressures to constrain genome size, rates of development, and stability in reproductive strategies (Renzaglia et al ., 1995).…”