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 homwort 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 Pellia 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 of the 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 pollen‐dispersed sperm indicate operation of a nucleotypic effect in archegoniates with biflagellated sperm. This effect may be on sperm cell functioning, which in turn 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.…”

Vegetative and reproductive innovations of early land plants: implications for a unified phylogeny

“…Notothylas occurs in disturbed sites that presumably select for rapid generation time and reduced complexity of both life cycle phases. In general, the rate of genomic evolution, and consequently phenotypic change, is greater in small organisms that grow and reproduce rapidly, a phenomenon that in turn is often correlated with low genome size (Niklas 1997;John & Miklos 1988;Renzaglia et al 1995). Thus, the interpretation of small ephemeral taxa such as Notothylas among anthocerotes and Riccia among hepatics as derived is consistent with life history phenomena and the seasonal instability experienced by these plants.…”

Motile Gametes of Land Plants: Diversity, Development, and Evolution

“…Successive cellular coils are not separated from each other. Individualization of coils is complete in most ferns (Figures 10B to D), but it is not complete in the anterior-most coil of Equisetum gametes (Figures 1, 10A) (Renzaglia et al, 2001b). A feature peculiar to fern gametes is that the coiled cylindrical nucleus is surrounded on two or three sides by the broad band of spline microtubules (Figures 9B,11,12,32C,34A,B).…”

“…Possibly actin filaments, the individual fibers in this band range from 6 to 12 nm in diameter. In Equisetum and Ophioglossum the band is more complex and is differentiated into two zones of distinct substructure: a fibrous portion that runs along the leading edge of the cell and a striated portion that overlies the MLS ( Figures 25G and 32 C, D) (Renzaglia et al, 2001b). The upper row of basal bodies inserts into the striated portion ( Figures 27G, 28B).…”