TABLE 5 - uploaded by Karen S Renzaglia
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Haploid genome size in liverworts. Estimated DNA-Feulgen per nucleus genome size Specimen Mean ? SE N (pg)
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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...
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Context 1
... genome size -Of the bryophytes examined, the two homworts-Notothylas orbicularis and Phae- oceros laevis-show the smallest genome sizes, 0.17 pg and 0.27 pg, respectively (Table 4). The six liverworts exhibit appreciable diversity in levels of sperm DNA con- tent with values ranging from 0.49 pg in Blasia pusilla to 4.05 pg in Pellia epiphylla (Table 5). Intermediate genome sizes were found for Lophozia capitata (0.73 pg DNA), Bazzania trilobata (1.03 pg DNA), Riccardia multifida (1.31 pg DNA), and Dumortiera hirsuta (1.58 pg DNA) ( Table 5). ...
Context 2
... six liverworts exhibit appreciable diversity in levels of sperm DNA con- tent with values ranging from 0.49 pg in Blasia pusilla to 4.05 pg in Pellia epiphylla (Table 5). Intermediate genome sizes were found for Lophozia capitata (0.73 pg DNA), Bazzania trilobata (1.03 pg DNA), Riccardia multifida (1.31 pg DNA), and Dumortiera hirsuta (1.58 pg DNA) ( Table 5). A second population of Lophozia capitata con- tained antheridia with spermatogenous cells in the pro- liferative stage of development. ...
Citations
... Following the diversification of Ginkgo and cycads, all vestiges of basal bodies and flagella were lost in the remaining seed plants that utilize pollen tubes to deliver non-motile sperm to egg cells (Southworth and Cresti, 1997). Male gametes provide a wealth of biological information, including biodiversity and cell differentiation and evolution (Garbary et al., 1993;Renzaglia et al., 1995;Renzaglia and Garbary, 2001;Renzaglia et al., 2000;Lopez-Smith and Renzaglia, 2008;Lopez and Renzaglia, 2014). Of the range of microscopic techniques utilized to characterize plant spermatozoids, SEM provides the most direct means of elucidating cell shape, and flagella number, length and arrangement. ...
The only motile cells produced in land plants are male gametes (spermatozoids), which are reduced to non-flagellated cells in flowering plants and most gymnosperms. Although a coiled architecture is universal, the complexity of land plant flagellated cells varies from biflagellated in bryophytes to thousands of flagella per gametes in the seed plants Ginkgo and cycads. This wide diversity in number of flagella is associated with vast differences in cell size and shape. Scanning electron microscopy (SEM) has played an important role in characterizing the external form, including cell shape and arrangement of flagella, across the varied motile gametes of land plants. Because of the size and scarcity of released swimming sperm, it is difficult to concentrate them and prepare them for observation in the SEM. Here we detail an SEM preparation technique that yields good preservation of sperms cells across plant groups.
... 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. They argued that high levels of atmospheric CO 2 as demonstrated in vitro for angiosperms (Edwards, 2003;Franks et al., 2012;Lomax et al., 2012) and paleopolyploidy may have resulted in exceptionally long guard cells. ...
As one of the earliest plant groups to evolve stomata, hornworts are key to understanding stomata origin and function. Hornwort stomata are large and scattered on sporangia that grow from their bases and release spores at their tips. We present data from development and immunocytochemistry that identify a role for hornwort stomata that is correlated with sporangial and spore maturation. We measured guard cells across the genera with stomata to assess developmental changes in size and to analyze any correlation with genome size. Stomata form at the base of the sporophyte in the green region, where they develop differential wall thickenings, form a pore and die. Guard cells collapse inwardly, increase in surface area and remain perched over a substomatal cavity and network of intercellular spaces that is initially fluid filled. Following pore formation, the sporophyte dries from the outside inwardly and continues to do so after guard cells die and collapse. Spore tetrads develop in spore mother cell walls within a mucilaginous matrix, both of which progressively dry before sporophyte dehiscence. A lack of correlation between guard cell size and DNA content, lack of arabinans in cell walls, and perpetually open pores are consistent with inactivity of hornwort stomata. Stomata are expendable in hornworts as they have been lost twice in derived taxa. Guard cells and epidermal cells of hornworts show striking similarities with the earliest plant fossils. Our findings identify an architecture and fate of stomata in hornworts that is ancient and common to plants without sporophytic leaves.
... It is an open question whether these features are connected with the gametophyte dominant life cycle. However , it has been suggested that in archegoniate plants producing biflagellated sperm gametes (such as early land plants), lower DNA contents afford a selective advantage through a nucleotypic effect on sperm cell efficiency and effectiveness, which in turn influences reproductive success [79]. ...
Genes encoding ribosomal RNA (rDNA) are universal key constituents of eukaryotic genomes, and the nuclear genome harbours hundreds to several thousand copies of each species. Knowledge about the number of rDNA loci and gene copy number provides information for comparative studies of organismal and molecular evolution at various phyloge-netic levels. With the exception of seed plants, the range of 45S rDNA locus (encoding 18S, 5.8S and 26S rRNA) and gene copy number variation within key evolutionary plant groups is largely unknown. This is especially true for the three earliest land plant lineages Marchan-tiophyta (liverworts), Bryophyta (mosses), and Anthocerotophyta (hornworts). In this work, we report the extent of rDNA variation in early land plants, assessing the number of 45S rDNA loci and gene copy number in 106 species and 25 species, respectively, of mosses, liverworts and hornworts. Unexpectedly, the results show a narrow range of ribosomal locus variation (one or two 45S rDNA loci) and gene copies not present in vascular plant lin-eages, where a wide spectrum is recorded. Mutation analysis of whole genomic reads showed higher (3-fold) intragenomic heterogeneity of Marchantia polymorpha (Marchantio-phyta) rDNA compared to Physcomitrella patens (Bryophyta) and two angiosperms (Arabi-dopsis thaliana and Nicotiana tomentosifomis) suggesting the presence of rDNA pseudogenes in its genome. No association between phylogenetic position, taxonomic adscription and the number of rDNA loci and gene copy number was found. Our results suggest a likely evolutionary rDNA stasis during land colonisation and diversification across 480 myr of bryophyte evolution. We hypothesise that strong selection forces may be acting against ribosomal gene locus amplification. Despite showing a predominant haploid phase and infrequent meiosis, overall rDNA homogeneity is not severely compromised in bryophytes.
... Thus, hornworts have some of the largest stomata and the smallest genome sizes. Those of M. hornum are larger than those of Plagiomnium cuspidatum despite a smaller genome size, and the same is true when comparison is made between Funaria and Physcomitrella (Voglmayr, 2000; Renzaglia et al., 1995; Rensing et al., 2008) and between the two Polytrichum species (Table 1). Similarly, there are wide disparities between closely related taxa in pore shapes, the presence or absence of subsidiary cells and stomatal orientation (Table 1,Fig. ...
Following the consensus view for unitary origin and conserved function of stomata across over 400 million years of land plant evolution, stomatal abundance has been widely used to reconstruct palaeo-atmospheric environments. However, the responsiveness of stomata in mosses and hornworts, the most basal stomate lineages of extant land plants, has received relatively little attention. This study aimed to redress this imbalance and provide the first direct evidence of bryophyte stomatal responsiveness to atmospheric CO2.
A selection of hornwort (Anthoceros punctatus, Phaeoceros laevis) and moss (Polytrichum juniperinum, Mnium hornum, Funaria hygrometrica) sporophytes with contrasting stomatal morphologies were grown under different atmospheric CO2 concentrations ([CO2]) representing both modern (440 p.p.m. CO2) and ancient (1500 p.p.m. CO2) atmospheres. Upon sporophyte maturation, stomata from each bryophyte species were imaged, measured and quantified.
Densities and dimensions were unaffected by changes in [CO2], other than a slight increase in stomatal density in Funaria and abnormalities in Polytrichum stomata under elevated [CO2].
The changes to stomata in Funaria and Polytrichum are attributed to differential growth of the sporophytes rather than stomata-specific responses. The absence of responses to changes in [CO2] in bryophytes is in line with findings previously reported in other early lineages of vascular plants. These findings strengthen the hypothesis of an incremental acquisition of stomatal regulatory processes through land plant evolution and urge considerable caution in using stomatal densities as proxies for paleo-atmospheric CO2 concentrations.
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... It is possible that ferns with large sperm are restricted to wet environments due to reduced sperm swimming efficiency. The relationship between genome size and sperm size has not been well explored in plants, but Renzaglia et al. (1995) noted a strong relationship between genome size, sperm size, and sperm complexity in bryophytes. Additionally, plants with biflagellate sperm, including bryophytes and some lycophytes, have significantly smaller genomes on average than ferns (Leitch et al. 2005), which have multiflagellate sperm. ...
Genome size is known to correlate with a number of traits in angiosperms, but less is known about the phenotypic correlates of genome size in ferns. We explored genome size variation in relation to a suite of morphological and ecological traits in ferns. Thirty-six fern taxa were collected from wild populations in Ontario, Canada. 2C DNA content was measured using flow cytometry. We tested for genome downsizing following polyploidy using a phylogenetic comparative analysis to explore the correlation between 1Cx DNA content and ploidy. There was no compelling evidence for the occurrence of widespread genome downsizing during the evolution of Ontario ferns. The relationship between genome size and 11 morphological and ecological traits was explored using a phylogenetic principal component regression analysis. Genome size was found to be significantly associated with cell size, spore size, spore type, and habitat type. These results are timely as past and recent studies have found conflicting support for the association between ploidy/genome size and spore size in fern polyploid complexes; this study represents the first comparative analysis of the trend across a broad taxonomic group of ferns.
... Orchidaceae; Jones et al. 1998). However, in other groups, chromosome number is not a predictor of genome size; indeed, previous studies found a negative correlation between chromosome number and genome size (in several angiosperm groups or in threatened plants; Vinogradov 2001Vinogradov , 2003 or no correlation at all (in bryophytes; Renzaglia et al. 1995). ...
The nuclear DNA content data available in “A genome size database in the Asteraceae” (GSAD: www.asteraceaegenomesize.com) have been analyzed, together with other parameters (i.e. ecological, karyological, cytogenetic), in order to establish hypotheses on the systematic, phylogenetic and evolutionary aspects of genome size in one of the largest angiosperm families. The novelty of this work is a comprehensive analysis of the whole family with the following aims: (1) to update the knowledge of genome size values in the Asteraceae; (2) to infer evolutionary trends of genome size, compared with other plant groups; and (3) to detect gaps in this field in the family and outline further research priorities. The analysis of this dataset shows that most Asteraceae genomes (57.23%) range from very small (1C 1.4 pg) to small (1C 3.5 pg). Gains and losses of DNA occur throughout the phylogeny of the family but although ancestral values for the basal nodes remain mostly equivocal, often small and very small ancestral genome sizes are reconstructed. Most genome size data (96.74%) are concentrated in five tribes, which broadly reflect their species richness. The relationships between genome size and other cytogenetic and ecological features have been analyzed and discussed, highlighting several general patterns. Further studies are needed to fill the gaps in genome size knowledge in the Asteraceae and more detailed research in some groups could provide information about mechanisms regulating genome expansions and contractions.
... Leitch and Leitch (2013) emphasized the need for genome size estimates for hornworts to strengthen our understanding of genome size evolution in land plants. Renzaglia et al. (1995) estimated the genome size for Notothylas orbicularis (1C-value = 0.17 pg) and Phaeoceros laevis (1C-value = 0.27 pg), but confirmation from flow cytometric measurements have been called for (Voglmayr 2000). Nevertheless, cytological data suggest small genome sizes for hornworts, as they have low chromosome numbers (n = 4-6 with a number of accessory chromosomes), small chromosome sizes, and an apparent rarity of polyploidy (e.g., Rink 1935;Proskauer 1957;Przywara and Kuta 1995). ...
... The very small genome sizes confirm the expectations based on small chromosome size and number. Additionally, our estimates for N. orbicularis and P. laevis closely match those obtained by Renzaglia et al. (1995), differing by less than 3% and confirming the accuracy of those measurements. Further species coverage is required to determine if all hornwort taxa have small genomes and whether an increase in genome size is restricted to the most recently divergent clades. ...
... Beyond learning more about patterns of DNA content variation in hornworts, there is much to be discovered regarding the biological significance of this variation. Renzaglia et al. (1995) put forth a compelling hypothesis relating genome size to sperm size and complexity in a sample of hornworts, mosses, and liverworts. Other morphological features that could be explored include cell size and spore size. ...
As our knowledge of plant genome size estimates continues to grow, one group has continually been neglected: the hornworts. Hornworts (Anthocerotophyta) have been traditionally grouped with liverworts and mosses because they share a haploid dominant life cycle; however, recent molecular studies place hornworts as the sister lineage to extant tracheophytes. Given the scarcity of information regarding the DNA content of hornworts, our objective was to estimate the 1C-value for a range of hornwort species within a phylogenetic context. Using flow cytometry, we estimated genome size for 36 samples representing 24 species. This accounts for roughly 10% of known hornwort species. Haploid genome sizes (1C-value) ranged from 160 Mbp or 0.16 pg (Leiosporoceros dussii) to 719 Mbp or 0.73 pg (Nothoceros endiviifolius). The average 1C-value was 261 ± 104 Mbp (0.27 ± 0.11 pg). Ancestral reconstruction of genome size on a hornwort phylogeny suggests a small ancestral genome size and revealed increases in genome size in the most recently divergent clades. Much more work is needed to understand DNA content variation in this phylogenetically important group, but this work has significantly increased our knowledge of genome size variation in hornworts.
... j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / y m p e v polymorpha (Ishida, 1961a,b; Sparrow et al., 1972), Riccia (Sparrow et al., 1972) and Conocephalum conicum (Taylor et al., 1982). Renzaglia et al. (1995) surveyed DNA content in six liverworts (Bazzania trilobata, Blasia pusilla, Dumortiera hirsuta, Lophozia capitata , Pellia epiphylla and Riccardia multifida). Recently, Temsch et al. (2010) estimated the 1C-value for 43 species. Of the three supported liverwort clades, genome size estimates are lacking for the Haplomitriopsida, and ther ...
... A phylogenetic tree was reconstructed including taxa from the present study as well as taxa from Temsch et al. (2010) and Renzaglia et al. (1995), using approximately 1000 nucleotides of (continued on next page) the plastid gene rbcL. The rbcL sequences were either downloaded from GenBank or newly generated at the University of Connecticut (using methods in Forrest and Stotler (2004)) or Duke (using methods in Davis (2004)). ...
... To test if changes in genome size are associated with the evolution of monoecy in liverworts, variation in genome size between different breeding systems was analyzed. Additional 1C-value estimates were included from Temsch et al. (2010) and Renzaglia et al. (1995). Breeding system for each species was determined from various taxonomic keys and literature sources (Crum, 1991; Godfrey, 1977; Schuster, 1992), and was classified as monoecious (n = 39), dioecious (n = 83), or both monoceious and dioecious (n = 8). ...
... From the biciliated ancestral state, multiciliated sperm evolved at least three times: twice in the lycophytes and once in the common ancestor of monilophytes and seed plants (reviewed in Renzaglia & Garbary, 2001). The increase in cilia number correlates with an increase in both sperm cell body size and nuclear DNA content (in part caused by polyploidy) (Renzaglia & Duckett, 1991;Renzaglia et al., 1995;Renzaglia & Garbary, 2001). Although there is no obvious evolutionary driver for this dramatic increase, it may have provided a way of enabling sperm cell motility in the reproductive context of seed plants. ...
Eukaryotic cilia/flagella are ancient organelles with motility and sensory functions. Cilia display significant ultrastructural conservation where present across the eukaryotic phylogeny; however, diversity in ciliary biology exists and the ability to produce cilia has been lost independently on a number of occasions. Land plants provide an excellent system for the investigation of cilia evolution and loss across a broad phylogeny, because early divergent land plant lineages produce cilia, whereas most seed plants do not. This review highlights the differences in cilia form and function across land plants and discusses how recent advances in genomics are providing novel insights into the evolutionary trajectory of ciliary proteins. We propose a renewed effort to adopt ciliated land plants as models to investigate the mechanisms underpinning complex ciliary processes, such as number control, the coordination of basal body placement and the regulation of beat patterns.
Contents
Summary
526
I.
Introduction
526
II.
Plant cilia: a model for evolution and development
530
III.
Future perspectives: Marchantia and Ceratopteris as models for cilia research
535
Acknowledgements
536
References
536
... Currently, there are no reliable genome size data for hornworts. Data for two species were reported by Renzaglia et al. (1995) (i.e., Notothylas orbicularis 1C ¼ 0.17 pg, Phaeoceros laevis 1C ¼ 0.27 pg) and their values are both at the lower end of those found in either mosses or liverworts. However, the Feulgen microdensitometry technique used to measure genome size did not follow best practice recommendations (e.g., unsuitable storage of nuclei prior to analysis, use of animal cells as calibration standards, use of highly condensed sperm nuclei, Temsch et al. 1998;Voglmayr 2000). ...
... Since this group of homosporous lycopods can reach high chromosome numbers (up to 2n ¼ c. 510 in Phylloglossum (Blackwood 1953) and 2n ¼ c. 556 in Huperzia prolifera (Tindale and Roy 2002) -the highest for any lycophytes) larger genomes may be encountered as data increase. However, genomes as large as some Isoetaceae seem unlikely in all but Phylloglossum since it has been suggested that there are constraints on genome size in groups with biflagellate sperm (i.e., Lycopodiaceae (excluding Phylloglossum), Selaginellaceae and all non-vascular plants, Renzaglia et al. 1995). The hypothesis states that for species with only two flagella there is an upper limit to genome size determined by the efficiency with which the flagella can move the sperm from the antheridia to the archegonia to effect fertilization. ...
... Indeed, as noted above the largest lycophyte genomes so far reported are indeed in Isoetaceae which have c. 20 flagella per sperm (Renzaglia et al. 1995). ...
In this timely new 2-volume treatise, experts from around the world have banded together to produce a first-of-its-kind synopsis of the exciting and fast moving field of plant evolutionary genomics. In Volume I of Plant Genome Diversity, an update is provided on what we have learned from plant genome sequencing projects. This is followed by more focused chapters on the various genomic "residents" of plant genomes, including transposable elements, centromeres, small RNAs, and the evolutionary dynamics of genes and non-coding sequences. Attention is drawn to advances in our understanding of plant mitochondrial and plastid genomes, as well as the significance of duplication in genic evolution and the non-independent evolution among sequences in plant genomes. Finally, Volume I provides an introduction to the vibrant new frontier of plant epigenomics, describing the current state of our knowledge and the evolutionary implications of the epigenomic landscape.
