ENDOPHYTIC ALGAE OF CHONDRUS CRISPUS (RHODOHYTA). II. ACROCHAETE HETEROCLADA SP. NOV., A. OPERCULATA SP. NOV., AND PHAEOPHILA DENDROIDES (CHLOROPHYTA)1

The occurrence of three endophytic green algae within Chondrus crispus Stackh. is reported. Two of them are new to science and are described as Acrochaete heteroclada Correa and Nielsen sp. nov. and A. operculata Correa and Nielsen sp. nov. The algae were studied in unialgal culture and in association with the host following infection of C. crispus under laboratory conditions. The experimental infection showed A. heteroclada to be initially epiphytic, with endophytic filaments growing into the cortex of the host during late infection. A. operculata is entirely endophytic when associated with the host. Phaeophila dendroides (Crouan frat.) Batters behaves as an epiphyte at 15 and 24°C but penetrates the host tissues at 20°C. For all three species, a close physical association with the host is established only when zoospores settle and germinate on the surface of C. crispus.     

WATER MOTION AND MORPHOLOGY IN CHONDRUS CRISPUS (RHODOPHYTA)1

Morphological variability of intertidal Chondrus crispus Stackh. fronds along a small open rocky coast was related to wave exposure and emersion. Cluster analysis revealed two well-defined morphologies: filiform and planiform, named the N morphotype and B morphotype, respectively. We propose a rapid method of classifying fronds based on the morphology of the cross section at half the height on the thallus. The N morphotype is characterized by fewer dichotomies per unit length, a circular cross section with a large inner cortex, and narrow fronds. It is abundant at low intertidal and exposed sites. The B morphotype is characterized by more dichotomies, smaller sizes, a subelliptical or flattened cross section, and broad fronds. It is abundant at high intertidal sites in sheltered areas. Regression analysis revealed a major effect of water movements on frond morphology with respect to tidal level, which was more evident at high intertidal levels. No relationships were observed between morphology and life history phases.     

CUTICLES FROM CHONDRUS CRISPUS (RHODOPHYTA)1

A simple, nondestructive physical process was developed for routinely isolating the outermost layers from female, male, and sporophyte fronds of Chondrus crispus Stack-house. Yields of pure cuticles from apical segments ranged from 0.74 to 2.35% on a dry weight basis after 5–7 d of culture. These undegraded cuticles were examined by electron microscopy (scanning and transmission electron microscopy), spectroscopy (infrared and X-ray), and chemical means. Cuticles isolated from female or male fronds were characterized by parallel arrays of electron-dense lamellae (typically 6–14) alternating with more electron-transparent regions. The thickness and uniformity of these lamellae provide the physical basis for the iridescence characteristic of C. crispus fronds. Sporophyte fronds are not iridescent. This phenomenon may be explained by the fewer electron-dense cuticular lamellae (usually three to seven) and the fact that these lamellae anastomose freely to form a thin cuticle with a highly irregular substructure. Elements detected by X-ray analysis, in addition to carbon and oxygen, included Mg, Br, S, and Ca in both gametophyte and sporophyte cuticles. Major features of FTIR spectra of all cuticles were absorbances due to proteins. A strong band, indicative of sulfate ester, occurred near 1250 cm^?1 in all cuticle preparations. Gametophyte, but not sporophyte, cuticles absorbed at 935, 846, and 800 cm^?1 consistent with the presence of kappa and/or iota carrageenan. Amino acid analyses showed that sporophyte and gametophyte cuticles were generally similar in gross composition. All contained proline as the principal residue together with significant amounts of cysteine, methionine, and lysine. Protein contents calculated from these analyses ranged from 37.6 to 44.4% on a dry weight basis as compared to 51.5–56.7% calculated from total nitrogen values. Up to 75% of the cuticle mass was solubilized by sodium dodecyl sulfate-β-mercaptoethanol. Three similar migrating bands were seen in female and male cuticle extracts on sodium dodecyl sulfate–polyacrylamide gel electrophoresis; however, none of the three weaker bands from sporophyte cuticles comigrated with those from gametophytes. Chloroform-methanol extraction removed < 3.3% of the cuticle mass, suggesting that lipids were minor components.     

LIFE HISTORY PHASES AND THE BIOMECHANICAL PROPERTIES OF THE RED ALGA CHONDRUS CRISPUS (RHODOPHYTA)

Chondrus crispus Stackhouse alternates between two isomorphic life history phases that differ in cell-wall phycocolloid composition. It has been long hypothesized that the gametophyte, with strong-gelling kappa-type carrageenans, is mechanically superior to the tetrasporophyte, with nongelling lambda-type carrageenans, which could contribute to the observed gametophytic dominance in many wave-swept environments. Standard mechanical tests were performed on distal tissues of C. crispus sampled from a range of environments in Narragansett Bay, Rhode Island, using a tensometer equipped with a video extensometer. Life history phase was by far the most important determinant of mechanical properties, whereas environmental factors had only modest influence (vertical distribution) or no effect (exposure); gametophytic distal tissues were 43% stronger, 21% more extensible, and 21% stiffer than tetrasporophytic distal tissues. However, the superior strength of gametophytic tissues was not evident at the stipe/holdfast junction (where breakage typically occurs), and the two phases were equally susceptible to dislodgment by a given force. The primary ecophysiological role of carrageenans in C. crispus may not be the provision of a structure to resist wave action.     

PHOSPHORUS AND NITROGEN NUTRITION IN CHONDRUS CRISPUS (RHODOPHYTA): EFFECTS ON TOTAL PHOSPHORUS AND NITROGEN CONTENT,CARRAGEENAN PRODUCTION,AND PHOTOSYNTHETIC PIGMENTS AND METABOLISM1

The existence of a phenomenon in phosphorus (P) nutrition comparable to the “Neish effect” in nitrogen (N) nutrition (an inverse relation between seawater N enrichment and carrageenan content) was investigated in the temperate red alga Chondrus crispus Stackhouse. Plants were preconditioned for 17 d and then cultured under varying enrichments of P (0, 3, 6, 10, 15 μM P·wk^?1) and a constant N enrichment (53.5 μM N·wk^?1) for 5 wk. Tissue total P, tissue total N, and carrageenan contents were then determined. Identical experiments were performed using C. crispus collected during the fall, winter, spring, and summer seasons. The procedure was repeated using material collected during the following fall season and cultured under constant P (6 μM P·wk^?1) and varying N enrichments (0, 3, 6, 10, 25 μM N·wk^?1). In the fall (P) experiment, carrageenan content was the highest [53.1 ± 0.3% DW (dry weight)], and tissue total P content was the lowest (1.71 ± 0.27 mg P·g DW^?1) in plants that received no P enrichment. Carrageenan content was stable (46.1 ± 1.8% DW) for plants given enrichments of 3 μM P·wk^?1 and greater. Thus, a decrease in carrageenan content, concomitant with an increase in tissue total P content, was observed, but only at tissue total P levels below 2 mg P·g DW^?1. As these levels were always higher than 2 mg P·g DW^?1 in the winter, spring, and summer experiments, carrageenan content remained constant within each season at 46.2 ± 1.3, 43.1 m 0.7, and 44.5 ± 0.6% DW, respectively. Nitrogen enrichment of plants collected in the fall did not affect carrageenan content, which was stable at 49.3 ± 0.9% DW. When these plants were compared with those of the previous fall experiment (6 μM P·wk^?1 and 53.5 μM N·wk^?1), a slight increase in carrageenan content was noted. Thus, at sufficiently high concentration, N also decreased carrageenan content in C. crispus. Phosphorus nutrition had no significant effect on photosynthesis versus irradiance parameters (P_max, α, R_d, I_c, and I_k), the contents of the photosynthetic pigments chlorophyll-a, phycoerythrin (PE), phycocyanin (PC), and allophycocyanin (APC), and the ratios PE:APC and PC:APC. In contrast, N nutrition affected both P_maxand the photosynthetic pigment contents. The data indicate that N limitation reduces the number of phycobilisomes but not their size. The greater reduction in phycobiliprotein than chlorophyll-acontent corroborates the natural bleaching phenomenon regularly observed in C. crispus populations during summer when N levels are generally low in seawater. These results suggest that C. crispus in the temperate waters of the Bay of Fundy may experience N limitation, but P limitation is unlikely.     

REDOX SENSITIVITY AND LIGHT MODULATION OF ENZYME ACTIVITY IN THE RHODOPHYTES GRACILARIA TIKVAHIAE AND CHONDRUS CRISPUS1

One of the cysteine residues believed to be necessary for reductive light activation is lacking in the only red algal NADP-linked glyceraldehyde-3-P dehydrogenases for which sequences are available, namely Gracilaria verrucosa (Hudson) Papenfuss and Chondrus crispus Stackhouse. Consistent with the mechanism of light modulation proposed for this enzyme, which involves reduction of domain movement-restricting disulfide bonds, it is not reductively activated in Chondrus crispus extracts, and it is not light-activated in whole cells or dithiothreitol (DTT) activated in extracts of the North American species Gracilaria tikvahiae McLachlan. Fructosebisphosphatase and glucose-6-P dehydrogenase, two enzymes for which sequence information from these algae is not yet available, are both activated in crude extracts by DTT treatment, but only fructosebisphosphatase is light-activated in intact Gracilaria.     

HOST SPECIFICITY IN THE RED ALGAL PARASITES BOSTRYCHIOCOLAX AUSTRALIS AND DAWSONIOCOLAX BOSTRYCHIAE (CHOREOCOLACACEAE,RHODOPHYTA)1

The determinants of host specificity, which are poorly understood in red algal parasites, were studied in the red algal parasites Bostrychiocolax australis Zuccarello et West and Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita. Culture studies were performed to determine host range, sites of host resistance, and genetics of transmission of resistance. Both species parasitize Bostrychia radicans (Montagne) Montagne, whereas Bostrychiocolax australis also parasitizes Bostrychia moritziana (Sonder ex Kützing) J. Agardh and Stictosiphonia kelanensis (Grunow ex Post) R. J. King et Puttock. Isolates of B. radicans resistant to both parasites were found worldwide, often within the same population as susceptible isolates. On resistant Bostrychia species and isolates, specificity was manifested at three stages: 1) host penetration, in which the spore germ peg failed to penetrate the host cuticle/wall; 2) parasite–host cell fusion, in which the fusion cell died and the parasite died; and 3) growth, in which parasites grew but soon died; parasites rarely reproduced and infections did not continue in culture. Resistance to parasite infection was usually transmitted as a dominant trait and did not segregate as a single locus during meiosis. In certain crosses, transmission of resistance was non-mendelian.     

PHYLOGEOGRAPHIC PATTERNS INDICATE TRANSATLANTIC MIGRATION FROM EUROPE TO NORTH AMERICA IN THE RED SEAWEED CHONDRUS CRISPUS (GIGARTINALES,RHODOPHYTA)1

Inferring how the Pleistocene climate oscillations have repopulated the extant population structure of Chondrus crispus Stackh. in the North Atlantic Ocean is important both for our understanding of the glacial episode promoting diversification and for the conservation and development of marine organisms. C. crispus is an ecologically and commercially important red seaweed with broad distributions in the North Atlantic. Here, we employed both partial mtDNA Cox1 and nrDNA internal transcribed spacer region 2 (ITS2) sequences to explore the genetic structure of 17 C. crispus populations from this area. Twenty‐eight and 30 haplotypes were inferred from these two markers, respectively. Analysis of molecular variance (AMOVA) and of the population statistic Φ_ST not only revealed significant genetic structure within C. crispus populations but also detected significant levels of genetic subdivision among and within populations in the North Atlantic. On the basis of high haplotype diversity and the presence of endemic haplotypes, we postulate that C. crispus had survived in Pleistocene glacial refugia in the northeast Atlantic, such as the English Channel and the northwestern Iberian Peninsula. We also hypothesize that C. crispus from the English Channel refugium repopulated most of northeastern Europe and recolonized northeastern North America in the Late Pleistocene. The observed phylogeographic pattern of C. crispus populations is in agreement with a scenario in which severe Quaternary glaciations influenced the genetic structure of North Atlantic marine organisms with contiguous population expansion and locally restricted gene flow coupled with a transatlantic dispersal in the Late Pleistocene.     

TWO MORPHOLOGICALLY SIMILAR BIOLOGICAL SPECIES: CHONDRUS PINNULATUS AND C. ARMATUS (GIGARTINACEAE,RHODOPHYTA)1

The nature of the relationship between Chondrus pinnulatus (Harvey) Okamura f. pinnulatus and C. pinnulatus f. armatus (Harvey) Yamada et Mikami (Gigartinaceae, Rhodophyta) was investigated by comparative analysis of their biogeography, phenologies, life histories, gross and vegetative morphology, crossability, and upper thermal tolerance. The forma pinnulatus has a more northerly distribution in Japan and adjacent waters, exhibiting adaptation to the cooler regions, whereas the forma armatus has a more southerly range. The latter may be the result of a higher thermal tolerance. Both formae have a Polysiphonia-type life history and are similar in their internal vegetative morphology. They can, however, be distinguished by gross morphology: forma pinnulatus has wide, flattened axes, compressed to flattened ultimate segments and proliferations, while forma armatus has narrow, compressed to subterete axes and subterete to terete ultimate segments and proliferations. These differences persist in laboratory culture. All intraformae crosses were positive, with carpospores from the cross developing into fertile F₁ tetrasporophytes releasing tetraspores that developed into dioecious F₁ gametophytes, the female gametophytes of which formed normal cystocarps. This suggests that members of populations of each forma freely interbreed. Among interformae crosses, only some offspring derived from geographically distant strains bore normal cystocarps in the F₁ female gametophytes. Other crosses showed that interbreeding between populations of these two formae was blocked by various isolating mechanisms: incompatibility, hybrid inviability, and hybrid sterility. Reproductive isolation between f. pinnulatus and f. armatus is virtually complete in wild populations, because hybrid populations have not been found in the wild. In addition, these two entities can be considered biological species that are also referred to the taxonomic species, C. armatus and C. pinnulatus, because they do not overlap with regard to the morphology of the ultimate segments and proliferations. Subtle (but significant) gross morphological differences, partial interfertility between the two species, and deleterious hybridization in the area in which they occur sympatrically suggest that their evolutionary divergence was relatively recent.     

DIFFERENTIAL LOCALIZATION OF CARRAGEENAN GELLING SEQUENCES IN KAPPAPHYCUS ALVAREZII VAR. TAMBALANG (RHODOPHYTA) WITH FITC-CONJUGATED CARRAGEENAN OLIGOSACCHARIDES1

The ability of kappa (κ) and iota (ι) carrageenans to form gels is dependent upon the regular repeat of disaccharide units along the carbohydrate chain. Short, chemically- and enzymatically-purified fragments of κ and ι carrageenan were conjugated to fluorescein and used as specific hybridization probes for localization of κ and ι carrageenan gelling sequences within the cells walls and intercellular matrices of Kappaphycus alvarezii (Doty) Doty. The probes label cell walls and intercellular matrices under ionic conditions appropriate for gelation of κ and ι carrageenans. The distribution of κ and ι carrageenans in the matrix and cell walls of K. alvarezii was determined with respect to cell type (epidermis, cortex, medulla, and central axis) and age. The κ-probe labels the cell walls of all cell types except epidermal in both young and old tissues. In contrast, the ι-probe labels the cell walls of the epidermis in both young and old tissue and the cell walls of the thylles only in old tissue. Both probes label intercellular matrix material; however, ι-probe labelling is very much weaker than κ-probe labelling. The results indicate that FITC-conjugated carrageenan oligosaccharides are useful tools that provide information on gelling subunit distribution.     

ATTACHMENT AND FUSION OF GAMETES DURING FERTILIZATION OF PALMARIA SP. (RHODOPHYTA)1

Fertilization of cultured microscopic female gametophytes by spermatia from field-collected male gametophytes of Palmaria sp. was observed by light and transmission electron microscopy. Liberated spermatia had a prophase-arrested nucleus with a pair of polar rings. The protoplast of spermatia was covered with ca. a 3-μm-thick hyaline covering. After spermatium inoculation, the spermatial covering was attached specifically to the coat surrounding the cell wall of the trichogyne. The spermatial covering was eliminated only at the site of gamete attachment, resulting in direct attachment of the spermatial plasma membrane to the trichogyne within 5 min after spermatium inoculation. This direct attachment was followed by completion of spermatial nuclear division and cell wall formation. The polar rings disappeared before prometaphase. The cytoplasm of the binucleate spermatium invaded the trichogyne cell wall and subsequently fused with the trichogyne cytoplasm. The trichogyne could fuse with many spermatia, and many male nuclei (the derivative nuclei of spermatial nuclear division) could enter the trichogyne cytoplasm.     

COMPARATIVE STUDIES ON THE CELL WALLS OF SEXUAL AND ASEXUAL BANGIA ATROPURPUREA (RHODOPHYTA). II ELECTROPHORETIC PATTERNS OF POLYSACCHARIDES1

Cellulose acetate electrophoresis of the hot water soluble polysaccharide extracts from whole filaments, as well as base, mid and tip segments, of marine asexual and sexual Bangia atropurpurea (Roth) C. Ag. Yielded distinctive patterns which demonstrated that changes occur in the outer cell walls during sexual reproduction. Heterogeneity of the sulfated polysaccharide components isolated from outer cell walls was shown to be specifically related to sexual reproduction. Two components (Band I and II) were detected in extracts from tips of sexual filaments, whole only one (Band I) was present in the vegetative segments of all filaments and in asexual reproductive regions. The faster running component (Band II) was detected during the later stages of sexual development, prior to maturation.     

MONOCLONAL ANTIBODIES AS MOLECULAR MARKERS FOR THE INTRACELLULAR AND CELL WALL DISTRIBUTION OF CARRAGEENAN EPITOPES IN KAPPAPHYCUS (RHODOPHYTA) DURING TISSUE DEVELOPMENT1

Carrageenan, the major cell wall carbohydrate of certain red algae, is variable in structure and gelling properties. Sequence types include gelling (kappa and iota) and nongelling (lambda) types in addition to precursors, often in hybrid molecules containing more than one precursor and/or sequence type. Molecular markers to subunits were needed to study carrageenan synthesis, cell wall organization, and the relationship between structure and function. Monoclonal antibodies were produced to carrageenan, and their specificities were determined by competitive enzyme immunoassay. Antibodies were identified with specificities related to kappa, iota, and lambda carrageenan. The patterns of immunofluorescence localization on Kappaphycus alvarezii = Eucheuma alvarezii var. tambalang (Doty) sections were distinctive for each antibody. The antibody to a kappa-related epitope labeled mature tissue strongly; antibodies to an iota-related epitope and a lambda-related epitope labeled weakly, consistent with the kappa-enriched carrageenan produced by this alga. Kappa-related epitopes were distributed throughout the wall and matrix, whereas iota-related epitopes were concentrated in the middle lamella. Lambda-related epitopes were localized primarily at the plant cuticle where kappa and iota antigens were lacking. An antibody appeared to be specific for a precursor of the gelling subunits because it showed maximal wall and intracellular labeling at the youngest developmental stage. All antibodies labeled intracellular inclusions in the transition zone between the epidermis and medulla during the development of medullary cells from the peripheral meristem in young branches. The results demonstrate the intracellular synthesis of epitopes related to all major carrageenan subunits and their differential extracellular distribution.     

ULTRASTRUCTURE OF MEIOSIS IN DASYA BAILLOUVIANA (RHODOPHYTA). I. PROPHASE I1

This first of two papers on ultrastructural observations of meiosis in the red alga Dasya baillouviana (Gmelin) Montague describes stages of prophase I of meiosis. Although the five stages of prophase were originally derived from light microscopic studies, the same stages were utilized for this study based on the developmental sequence of the synaptonemal complex, which has the same morphology and mode of development as those reported for other red algae. The cytoplasm in early prophase sporocytes was typically less electron dense than either vegetative cells or sporocytes in later stages of meiosis. The reduction in density suggests clearing of ribosomes and other cytoplasmic components prior to conversion from sporophyte to gametophyte control. Leptotene cells often had an amorphous, chromatin-free area, function unknown, which was not obviously associated with any specific nuclear region. Diplotene cells were characterized by nuclei containing prominent ring-shaped nucleoli composed of a dark staining ring of material surrounding an electron-translucent “vacuole.” Packets of electron-dense, fibrillar material were often noted in the cytoplasm of late prophase cells. These packets are thought to he “nuage,” a term applied to large cytoplasmic aggregations of RNA in germ cells of several other phyla. It is suggested that nuage may represent a new infusion of ribosomal and messenger RNA for post-meiotic development. The division pales are established by late prophase and a single polar ring is found within each large “exclusion zone” in close association with a pore-free area of nuclear envelope. Both annulate lamellae and small, numerous vesicles are located in the exclusion zones. The significance of the various aspects of prophase I is discussed with the overall observation that this phase of meiosis in red algae is very similar to the process in higher plant and animal cells.     

COMPARATIVE STUDIES ON THE CELL WALLS OF SEXUAL AND ASEXUAL BANGIA ATROPURPUREA (RHODOPHYTA). I. HISTOCHEMISTRY OF POLYSACCHARIDES1

A comparative histochemical study of the nature and distribution of acidic and neutral cell wall polysaccharides was conducted on marine sexual and asexual filaments of the red alga Bangia atropurpurea (Roth) C. Ag. Outer and inner walls of this species were clearly partitioned according to staining and transmission electron microscopic characteristics. Neutral polysaccharides were detected in the outer coating (cuticle) but were absent from outer and inner walls of all filaments. Acidic polysaccharides were noted in the outer wall material but not in the inner wall layers of any filaments at any developmental stages. The major staining component of vegetative regions of sexual material and all regions of asexual filaments was a highly sulfated polymer. During sexual reproduction only there was a generalized change in the nature of the acidic component, characterized by a decrease in intensity of staining for sulfates in both male and female filaments and the appearance, in female filaments only, of polysaccharides which presumably were carboxylated. Spermatia attached to both male and female filaments in regions where sexual differentiation was initiated and where changes in the outer wall components commenced.     

A SPOROPHYTE CELL WALL PROTEIN OF THE RED ALGA PORPHYRA PURPUREA (RHODOPHYTA) IS A NOVEL MEMBER OF THE CHYMOTRYPSIN FAMILY OF SERINE PROTEASES1

A complementary DNA (cDNA) clone from a Porphyra purpurea (Roth) C. Agardh sporophyte-specific subtracted cDNA library was found to encode a protein similar to serine proteases of the chymotrypsin class. The encoded protein contains a typical signal peptide and is particularly similar to chymotrypsins in the regions surrounding the active site residues and the activation site where cleavage of the propeptide occurs. In addition, the six cysteine residues characteristic of chymotrypsins are conserved. However, two of the three residues of the active site His/Asp/Ser charge relay triad have been replaced, indicating that the protein is unlikely to have peptidase activity. Northern hybridization confirmed that this cDNA is derived from an abundant, sporophyte-specific messenger RNA (mRNA). The presence of signal peptide on the encoded protein and the abundance of its mRNA suggested that this protein might be localized in the cell wall. Consequently, sporophyte cell walls were isolated and a major protein having a molecular weight similar to that estimated for the encoded protein was purified. N-terminal sequence analysis indicated that this cell wall protein is identical to that encoded by the cDNA with the amino terminus of the mature protein beginning at the activation site. This cell wall structural protein appears to have evolved from a chymotrypsin-like progenitor but has been adapted to bind cell wall proteins and/or polysaccharides rather than to cleave proteins.     

A GLYCOPROTEIN NONCOVALENTLY ASSOCIATED WITH CELL‐WALL POLYSACCHARIDE OF THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA)1

The cells of the red microalga Porphyridium sp. (UTEX 637) are encapsulated in a cell wall of a negatively charged mucilaginous polysaccharide complex composed of 10 different sugars, sulfate, and proteins. In this work, we studied the proteins associated with the cell‐wall polysaccharide. A number of noncovalently associated proteins were resolved by SDS‐PAGE, but no covalently bound proteins were detected. The most prominent protein detected was a 66‐kDa glycoprotein consisting of a polypeptide of approximately 58 kDa and a glycan moiety of approximately 8 kDa containing N‐linked terminal mannose. In size‐exclusion chromatography, the 66‐kDa protein was coeluted with the polysaccharide and could be separated from the polysaccharide only after denaturation of the protein, indicating that the 66‐kDa protein was tightly bound to the polysaccharide. Western blot analysis revealed that the 66‐kDa protein was specific to Porphyridium sp. and P. cruentum, because it was not detected in the other species of red microalgae examined. Indirect immunofluorescence assay confirmed the location of the protein in the algal cell wall. The sequence of cDNA clone encoding the 66‐kDa glycoprotein, detected in our in‐house expressed sequence tag database of Porphyridium sp., revealed that this is a novel protein with no similarity to any protein in the public domain databases and our in‐house expressed sequence tag database of the red microalga Rhodella reticulata. The 66‐kDa protein bound polysaccharides from red algae but not from those of other origins tested. Possible roles of the 66‐kDa protein in the biosynthesis of the polysaccharide are discussed.     

A GAMETOPHYTE CELL WALL PROTEIN OF THE RED ALGA PORPHYRA PURPUREA (RHODOPHYTA) CONTAINS FOUR APPARENT POLYSACCHARIDE-BINDING DOMAINS1

A complementary DNA(cDNA)clone from a Porphyra purpurea (Roth) C. Agardh gametophyte-specific subtracted cDNA library was found to encode a protein containing a signal peptide and four very similar regions with a high degree of amino acid sequence similarity to the cellulose-binding domains of fungal celluloses. Northern hybridization analysis indicated that the messenger RNA of this cDNA is highly abundant in the gametophyte but not detectable in the sporophyte. In vitro translation of the cDNA in the presence of canine pancreatic microsomes demonstrated that the signal peptide is capable of directing the protein into the endoplasmic reticulum where it is glycosylated. Because these observations suggested a possible role as a gametophyte-specific cell wall protein, cell wall protein, were isolated and a major protein having a molecular weight similar to that estimated for the encoded protein was purified. N-terminal sequence analysis indicated that this was the protein encoded by the cDNA. The abundance and organization of this protein suggest a role as a cell wall structural protein involved in cross-linking polysaccharides.     

ULTRASTRUCTURE OF MEIOSIS IN DASYA BAILLOUVIANA (RHODOPHYTA). II. PROMETAPHASE I—TELOPHASE II AND POST-DIVISION NUCLEAR BEHAVIOR1

This is the second of two papers which together are the first comprehensive ultrastructural report of meiosis in a red alga. Many details of the meiotic process in Dasya baillouviana (Gmelin) Montagne are the same as those reported previously for mitotic cells in ceramialian red algae, but several characteristics seem unique to meiotic cells. The nucleus and nucleolus of meiotic cells are larger than those of mitotic cells and large accumulations of smooth ER are often found at the division poles during meiosis 1. The function of the ER accumulations is unknown. Importantly, both interkinesis and a simultaneous division of two separate nuclei during meiosis II was demonstrated. These new observations fail to support earlier speculation on higher red algae for a “uninuclear” meiosis (both nuclear divisions within the same nuclear envelope). However, following meiosis II the four nuclei migrate centripetally and possibly fuse in the center of the tetrasporangium. This post-division nuclear maneuvering is not understood, but our interpretation accounts for the earlier and erroneous impression of “uninuclear” meiosis. Perhaps the most important aspect of meiosis observed in Dasya is its basic adherence to the pattern commonly seen in higher plants and animals. This conservatism of the meiotic process lends further skepticism to the belief that red algae are extremely “primitive” organisms, although they undoubtedly represent a very “ancient” group of eukaryotic plants.     

THE BIOLOGY OF HARVEYELLA MIRABILIS (CRYPTONEMIALES; RHODOPHYCEAE). V. HOST RESPONSES FO PARASITE INFECTION1,2

The thallus of Harveyella mirabilis (Reinsch) Schmitz & Reinke is composed of vegetative rhizoidal cells growing intrusively between adjacent cells of the red algal hosts (Odonthalia and Rhodomela) and a protruding reproductive pustule. Although primarily composed of Harveyella cells, host medullary and cortical cells also occur in the emergent pustule. In both tissue regions, Harveyella cells are connected to host cells by secondary pit connections initiated by the host. Direct penetration of host cells by rhizoidal cells of Harveyella occasionally occurs, resulting in host cell death. Degeneration of host medullary cells beneath the pustule may result in a hollow branch and the cortical cells undergo cell division forming a thick palisade layer of randomly associated, photo-synthetically active cells. It is within these branches that the parasite overwinters vegetatively. Host medullary and cortical cells dispersed in the emergent pustule show few of the degenerative responses noted in host cells adjacent to parasite rhizoidal cells. Rather, host cell division, chloroplast division and photosynthetic assimilation of H¹⁴CO^?₃ all increase. Spherical virus-like solitary bodies (S-bodies) occur in all Harveyella cells and in all host cells attached to Harveyella by secondary pit connections. The possibility that these structures may induce the infective response in the host is discussed.