Donald F. Kapraun

Random amplified polymorphic DNA (RAPD) identification of genetic variation in three species ofPorphyra (Bangiales, Rhodophyta)

The random amplified polymorphic DNA (RAPD) technique was used to characterize three species ofPorphyra from the western North Atlantic and adjacent Gulf of Mexico. Twenty 10-mer primers were screened for DNA amplification usingPorphyra template DNA. Nine of these oligonucleotide primers, all (G+C)-rich, were positive or band-producing, but yielded poor or variable band resolution. Subsequent use of the universal 20-mer M 13 primer resulted in both clear band resolution with a minimum of secondary bands and a high degree of reproducibility. Amplification products for DNA from six regional isolates ofPorphyra carolinensis Coll et Cox,P. leucosticta Thuret in Le Jolis andP. rosengurttii Coll et Cox were compared to each other and toBangia atropurpurea (Roth) C. Agardh. Results provide evidence of both genetically hetero- and homogeneous populations. Use of the RAPD method with the M 13 primer yields amplification products which can be used to fingerprint specific genotypes. This procedure could be used to discriminate between hetero- and homokaryotic fusion products from previously characterized donor strains.

Karyology and agar analysis of the agarophyteGelidiella acerosa (Forsskål) Feldmannet Hamel from the Philippines

Microspectrophotometry with the DNA-localizing fluorochrome DAPI demonstrated ploidy level differences in tetrasporophytic and presumptive gametophytic phases ofGelidiella acerosa from the Philippines. Comparison of mean nuclear DNA (If) values to chicken erythrocytes (RBC) resulted in an estimate of 0.32 pg/2 C genome. Karyological studies with aceto-orcein revealed a chromosome complement of six bivalents during diakinesis of tetrasporocytes. The agar yield ranges from 13–24% dry weight, depending on the method of extraction. Agar extraction in 1 N NaOH resulted in an increased gel strength of 189 g cm−2 at 1.5% concentration. Infrared spectroscopy indicated a relatively high sulfate content in native agar. The low (61 °) melting temperature is indicative of high sulfation and small molecular size.

Quantification and characterization of nuclear genomes in commercial red seaweeds: Gracilariales and Gelidiales

Nuclear genome profiles were developed for representative species of the Gelidiales and Gracilariales using information from present and previous studies of cytogenetics, cytophotometry and DNA reassociation kinetics. Results indicate that species of Gracilaria and Gracilariopsis are characterized by distinct chromosome complements of n = 24 and n = 32, respectively, a narrow range of small genome sizes (2C = 0.35–0.45 pg) and a wide range of values for repeated and unique genome sequences. In contrast, the Gelidiales investigated are characterized by a wide range of chromosome complements, n = 6–29, a wider range of genome sizes (2C = 0.42–0.68 pg) and a large proportion of unique genome sequences. Nuclear genome sizes for species of the Gelidiales and Gracilariales are compared with estimates of other red algal orders including the Bangiales, Ceramiales and Gigartinales.

FIELD AND CULTURE STUDIES ON GROWTH AND REPRODUCTION OF CALLITHAMNION BYSSOIDES (RHODOPHYTA, CERAMIALES) IN NORTH CAROLINA1,2

The life history of Callithamnion byssoides Arnott ex Harv. in Hook. from North Carolina is shown to be of the Polysiphonia‐type. Cross‐gradient light‐temperature culture in 8:16 and 14:10 LD cycles was utilized to investigate the effects of light intensity, temperature and day‐length on growth and reproduction. Carposporophyte and tetrasporangium development were controlled by total light energy rather than photoperiod. Results of these studies explain the observed seasonal periodicity of growth and reproduction on the North Carolina coast. Variations between these results and previously published data for this species in Texas are explained in terms of ecotypic differentiation.

Inter- and intraspecific variation of nuclear DNA reassociation kinetics in the Gracilariales (Rhodophyta)

DNA reassociation kinetics were used to determine inter- and intraspecific variation in genome organization and complexities in species ofGracilaria andGracilariopsis. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repeated sequences varied from 13–95%. Three geographic populations ofGracilaria tikvahiae were similar with 13–27% repeated sequences.Gracilaria sp. cultivars G-1 and G-6 with 35% and 95% repeated sequences, respectively, were distinct from each other andG. tikvahiae. No pattern of genome organization and complexity was found which permitted a distinction betweenGracilaria andGracilariopsis. Comparison of the percent of unique and repetitive sequences (U/R) indicated a wide range of ratios, withGracilaria tikvahiae populations having the highest values (2.7–7.3) andGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis the lowest (0.05–1.80). Unique component complexities varied one order of magnitude, from 108 forGracilaria takvahiae to 107 forGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis. Information for genome size, organization and complexity is used to develop a nuclear genome profile forGracilaria blodgettii andGracilariopsis lemanieformis which are characterized by commercial grade agars having high gel strengths (> 700 g cm−2) and elevated melting temperatures (99 °C).

Nuclear genome characterization of the carrageenophyteAgardhiella subulata (Rhodophyta)

DNA reassociation kinetics were used to determine nuclear genome organization and complexity inAgardhiella subulata (Gigartinales, Rhodophyta). Results indicate the presence of three second-order components corresponding to fast (22%), intermediate (68%) and slow (10%) fractions. Thus, the genome consists of 90% repetitive sequences. Microspectrophotoometry with the DNA-localizing fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporophytic phases. Results indicate that meiosis occurs during tetrasporogenesis. Comparison of mean nuclear DNA (If) values to chicken erythrocytes (RBC) resulted in an estimate of 0.9 pg/2C genome forAgardhiella. Karyological studies using aceto-orcein revealed a chromosome complement of 2N = 44 in carposporangia and the presence of 22 bivalents during diakinesis of tetraspore mother cells.

Relationship of nuclear genome size to some reproductive cell parameters in the Florideophycidae (Rhodophyta)

Abstract Microspectrophotometry with the DNA-localizing fluorochrome 4′,6 diamidino-2-phenylindole was used to estimate nuclear genome sizes in nine species representing two orders of the Florideophycidae. Estimated 2C DNA spermatial contents in these taxa are in the range of 0.22–2.85 pg. Carpospore volume estimates determined by an image processing system for 24 species and geographical isolates representing four orders of Florideophycidae indicate mean volume ranges of 3644–233,210 μm3 for individual species, i.e. about two orders of magnitude. Estimates of carpospore numbers per cystocarp made with an image processing system indicate that carpospore volumes are negatively correlated (r = 0.716) with the number of carpospores produced per cystocarp. Three related trends were identified: (1) genome size is positively correlated with carpospore volume; (2) species with larger genomes produce fewer carpospores per cystocarp; and (3) species that produce larger carpospores produce fewer carpospores per cystocarp. These findings are discussed in the context of r– and K-selection and the evolution of nuclear genome size variation in these Florideophycidae.

Agar Analysis, nuclear genome quantification and characterization of four agarophytes (Gracilaria) from the Mexican Gulf Coast

DNA reassociation kinetics were used to determine nuclear genome organization and complexity in four species of Gracilaria (Gracilariales, Rhodophyta). In Gracilaria tikvahiae, G. caudata, G. cervicornis and G. divaricata, results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–46% and unique DNA ranged from 45–78%, Thermal denaturation (Tm) indicated guanine + cytosine (G + C) levels of 41.9–46.0 mol % G + C. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA content. Comparisons of mean nuclear DNA (If) values to chicken erythrocytes (RBC) resulted in an estimate of 0.37–0.40 pg/2C genomes for the four Gracilaria species. Total agar content following alkaline pretreatment ranged from 7–15% dry weight. Gel strengths were generally below commercial levels, ranging from 40–260 g cm−2 Nuclear genome profiles developed from information for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity as previously speculated.

Nuclear DNA content variation in the freshwater red algal orders Batrachospermales and Thoreales (Florideophyceae, Nemaliophycidae)

D.F. Kapraun, K.S. Braly and D.W. Freshwater. 2007. Nuclear DNA content variation in the freshwater red algal orders Batrachospermales and Thoreales (Florideophyceae, Nemaliophycidae). Phycologia 46: 54–62. DOI: 10.2216/06-18.1 A microspectrophotometric investigation of red algae in the exclusively freshwater orders Batrachospermales and Thoreales was initiated to determine the extent of nuclear DNA content variation and to corroborate the alternation of haploid and diploid nuclear DNA contents in gametophyte and sporophyte life history stages. Partial RuBisCO subunit (rbcL) sequences were generated and included in a larger data set for phylogenetic analyses to explore possible correlations between genome size and evolution. Results of rbcL analyses reflected those of previous studies, including the monophyly of the genus Sirodotia and family Lemaneaceae, and paraphyly of Batrachospermum. Static microspectrophotometry and the DNA-localizing fluorochrome DAPI (4′,6′-diamidodino-2-phenylindole) and red blood cell (chicken erythrocytes) standard were used to estimate nuclear DNA contents for 11 species in 6 genera in the Batrachospermales and the Thoreales. Estimated nuclear DNA content values ranged from 0.23 to 3.20 pg. Both estimated genome sizes and published chromosome numbers suggest a discontinuous distribution that can be explained in terms of ancestral polyploidy events. Results of this study suggest a possible correlation between polyploidy and the expression of the Batrachospermum or Lemanea morphological phenotypes. For isolates of three species, If (fluorescence) levels in 2C nuclei in presumptive gametophytes closely approximated 50% of the 4C values in presumptive sporophytes, consistent with an alternation of ploidy levels in a sexual life history.

Karyology and nuclear DNA quantification of four species of Chaetomorpha (Cladophorales, Chlorophyta) from the western Atlantic

Chromosome numbers are given for four species ofChaetomorpha from the warm temperate and tropical western Atlantic. The basic chromosome number is six, with three median and three submedian chromosomes.Chaetomorpha species represent a polyploid series, with numbers of 12, 18 and 24 found in the present study. Microspectrophotometry data for each species were quantified by reference to standards with known DNA contents. Results indicate similar 2X =1C=12 genome sizes forC. aerea (0.20 pg) andC. brachygona (0.26 pg), and forC. antennina (0.53 pg) andC. melagonium (0.58 pg). These findings are compared with karyological features ofCladophora species to characterize the karyology of the cladophoralean genome.