A PERSISTENT VIRUS INFECTION IN FELDMANNIA (PHAEOPHYCEAE)1

A virus infection is described within the unilocular sporangia of Feldmannia sp., a filamentous brown alga (Phaeophyceae). The alga is easily maintained in culture and vegetative growth is vigorous, but formation of icosahedral virions 150 nm in diameter completely displaces production of zoospores. The viruses, estimated at 1–5 × 10⁶ per sporangium, are eventually released by rupture of the sporangial wall. Deoxyribonucleic acid (DNA) isolated from the viruses can be readily digested with restriction endonucleases and consists of ca. 170 kbp of double-stranded DNA.     

INHERITANCE AND MEIOTIC ELIMINATION OF A VIRUS GENOME IN THE HOST ECTOCARPUS SZLZCULOSUS (PHAEOPHYCEAE)1

The marine brown alga Ectocarpus siliculosus (Dillwyn) Lyngbye is frequently infected by a latent DNA virus that multiplies in modified sporangia and gametangia of the host. We describe a polymerase chain reaction (PCR) procedure for the amplification and detection of viral DNA in Ectocarpus. PCR analysis of parents and progeny plants confirmed that virus DNA passes through meiosis like a Mendelian trait. An infected sporophyte produced equal numbers of gametophytes with and without the viral genome. Thus, meiosis in sexual populations of the host acts as a mechanism for the creation of virus-free progeny.     

ISOLATION AND CHARACTERIZATION OF A DNA VIRUS INFECTING FELDMANNIA SIMPLEX (PHAEOPHYCEAE)1

We report on the isolation and characterization of a virus that is formed in modified zoidangia of the marine brown alga Feldmannia simplex (Crouan) Hamel (Ectocarpales, Phaeophyceae). Isolated virus particles had a buoyant density of about 1.35 g·mL^?1 in CsCl equilibrium gradients. They contained one major polypeptide (MW = 55,000) and at least six additional polypeptides (MW = 15,000–120,000). Four of these proteins were glycosylated. The viral genome consisted of double-stranded DNA and formed two freely migrating fractions in pulsed-field-gel electrophoresis, namely linear DNA with a size of 220 kilobase pairs, and fragments of 10–60 kilobase pairs. However, electron microscopic examination revealed that a substantial fraction of the viral DNA occurred as closed circles. We suggest that the viral DNA in native particles is circular but tends to break at random sites during the preparation.     

LAMINARIOCOLAX SP. (PHAEOPHYCEAE) ASSOCIATED WITH GALL DEVELOPMENTS IN LESSONIA NIGRESCENS (PHAEOPHYCEAE)1

As part of a long‐term study on the biology and ecology of the intertidal kelp Lessonia nigrescens Bory, we report on the occurrence of gall development on this alga, identified the possible causal agent, and assessed the extent of the phenomenon in two wild stands of the host. Our results showed that galls affecting natural populations of L. nigrescens were associated with the infection by a filamentous brown algal endophyte of the genus Laminariocolax. Assignment to Laminariocolax of the endophytes isolated from cultured gall tissue was based on the (i) high internal transcribed spacer 1 (ITS1) sequence similarity and phylogenetic relationship between the Chilean isolates and several species of the genus Laminariocolax endophytic in other kelps, (ii) reproductive and vegetative features of the endophyte in culture, and (iii) anatomical agreement of fully developed galls of Lessonia with those described for other kelp galls caused by endophytic members of Laminariocolax. Unequivocal identification at the species level of the endophytes infecting Lessonia, however, awaits further studies.     

A MOLECULAR ANALYSIS OF ANALIPUS AND RALFSIA (PHAEOPHYCEAE) SUGGESTS THE ORDER ECTOCARPALES IS POLYPHYLETIC1

We report partial 18S ribosomal DNA sequences of Analipus japonicus (Harvey) Wynne and Ralfsia fungiformis (Grunnerus) Setchell et Gardner. These sequences were compared with the corresponding sequences of 13 brown algae representing six phaeophycean orders: Dictyotales, Ectocarpales, Fucales, Laminariales, Sphacelariales, and Syringodermatales. These 15 brown algae included 10 ectocarpoids representing nine ectocarpacean (sensu Gabrielson et al. 1989) families: Chordariaceae, Dictyosiphonaceae, Ectocarpaceae, Elachistaceae, Heterochordariaceae, Leathesiaceae, Punctariaceae, Ralfsiaceae, and Scytosiphonaceae. We addressed the controversial taxonomic placement of A. japonicus and R. fungiformis in the Ectocarpales by analysis of DNA sequences. Neighbor-joining and maximum parsimony-inferred phylogenies provided evidence that A. japonicus and R. fungiformis are not closely associated with the other representatives of the Ectocarpales. Bootstrap analyses suggest polyphyly of the order Ectocarpales (sensu Gabrielson et al.). However, our analysis failed to resolve the phylogenetic relationship between A. japonicus and R. fungiformis. Our results suggest that the ectocarpoids are just as distantly related to A. japonicus and R. fungiformis as they are to members of the advanced orders Desmarestiales, Dictyotales, Fucales, Laminariales, Sphacelariales, and Syringodermatales.     

First report of the Asian seaweed <Emphasis Type="Italic">Sargassum filicinum</Emphasis> Harvey (Fucales) in California,USA

We report the occurrence of the brown seaweed Sargassum filicinum Harvey in southern California. Sargassum filicinum is native to Japan and Korea. It is monoecious, a trait that increases its chance of establishment. In October 2003, Sargassum filicinum was collected in Long Beach Harbor. In April 2006, we discovered three populations of this species on the leeward west end of Santa Catalina Island. Many of the individuals were large, reproductive and senescent; a few were small, young but precociously reproductive. We compared the sequences of the mitochondrial cox3 gene for 6 individuals from the 3 sites at Catalina with 3 samples from 3 sites in the Seto Inland Sea, Japan region. The 9 sequences (469 bp in length) were identical. Sargassum filicinum may have been introduced through shipping to Long Beach; it may have spread to Catalina via pleasure boats from the mainland.     

MOLECULAR PHYLOGENY OF DISCOSPORANGIUM MESARTHROCARPUM (PHAEOPHYCEAE) WITH A REINSTATEMENT OF THE ORDER DISCOSPORANGIALES1

A molecular phylogenetic analysis of the little‐studied filamentous brown alga Discosporangium mesarthrocarpum (Meneghini) Hauck using rbcL and partial 18S rDNA sequences revealed that the species forms a monophyletic clade with Choristocarpus tenellus (Kütz.) Zanardini that is sister to all other brown algae. Although D. mesarthrocarpum has unique disk‐shaped plurilocular reproductive organs, D. mesarthrocarpum and C. tenellus share the following basic morphological features, which are considered to be plesiomorphic characters in the brown algae: (1) apical (and diffuse) growth; (2) uniseriate, subdichotomously branched filaments; (3) multiple chloroplasts per cell without pyrenoids; and (4) lack of heterotrichy and of phaeophycean hairs. The rbcL DNA sequence of an Australian D. mesarthrocarpum specimen showed considerable deviation from Mediterranean and Macaronesian specimens. Therefore, the presence of a second species in the genus is suggested; however, the taxonomic treatment of this putative species is not pursued in the present report. Regarding the higher‐ranking systematic position of D. mesarthrocarpum, reinstatement of Discosporangiaceae and Discosporangiales is proposed, and the inclusion of Choristocarpaceae in the order is also suggested. Under short‐day and long‐day culture conditions at 15°C–25°C, Mediterranean D. mesarthrocarpum exhibited a direct type of life history, with a succession of uniseriate filamentous thalli bearing characteristic disk‐shaped plurilocular zoidangia, but thalli did not survive at 10°C and below.     

SPECIES DELIMITATION,TAXONOMY, AND BIOGEOGRAPHY OF DICTYOTA IN EUROPE (DICTYOTALES,PHAEOPHYCEAE)1

Taxonomy of the brown algal genus Dictyota has a long and troubled history. Our inability to distinguish morphological plasticity from fixed diagnostic traits that separate the various species has severely confounded species delineation. From continental Europe, more than 60 species and intraspecific taxa have been described over the last two centuries. Using a molecular approach, we addressed the diversity of the genus in European waters and made necessary taxonomic changes. A densely sampled DNA data set demonstrated the presence of six evolutionarily significant units (ESUs): Dictyota dichotoma (Huds.) J. V. Lamour., D. fasciola (Roth) J. V. Lamour., D. implexa J. V. Lamour., D. mediterranea (Schiffn.) G. Furnari, D. spiralis Mont., and the newly described D. cyanoloma sp. nov., which was previously reported as D. ciliolata from the Mediterranean Sea. Species distributions, based on DNA‐confirmed occurrence records, indicate that all species are geographically confined to the NE Atlantic Ocean with the exception of D. dichotoma and D. implexa, which also occur in South Africa and Bermuda, respectively. To investigate potential hybridization between D. dichotoma and D. implexa, which were previously shown to be sexually compatible in culture, we compiled and analyzed sets of mitochondrial, plastid, and nuclear markers to detect putative hybrids or introgression in natural populations. Failure to detect natural hybrids indicates that effective pre‐ and postzygotic isolation mechanisms are at play in natural populations and supports the by‐product hypothesis of reproductive isolation.     

VIRUSLIKE PARTICLES IN THE MARINE ALGA CHORDA TOMENTOSA LYNGBYE (PHAEOPHYCEAE)1

Polyhedral viruslike particles 170 nm in diameter were found in 3-day-old spores of the brown alga Chorda tomentosa Lyngbye grown in unsterilized seawater. In sterile seawater, spores of the same species were free of these particles and cell wall development around naked settled, zoospores and subsequent spore germination proceeded, normally. Spores containing the putative virus particles did not develop cell walls or show signs of germination. Severe lysis of cell organelles always accompanied, the presence of these particles.     

REPRODUCTIVE PLASTICITY IN THE KELP ALARIA NANA (PHAEOPHYCEAE)1

Unlike terrestrial plants, reproductive control in algae has not been attributed to biotic factors or internal chemical signals. However, experimental removal of reproductive structures (sporophylls) from the kelp Alaria nana Shrader resulted in the development of functional reproducing structures on the vegetative frond in 45% (10/22) of the experimental plants but not on the control plants where sporophylls were left intact (n = 35). In naturally occurring Alaria nana, this compensatory reproductive response occurred at a low incidence and was restricted primarily to larger individuals in the population. Thus, compensation and developmental plasticity, mediated In plant size, may play an important role in how algae respond to reproductive tissue loss.     

SYNARTHROPHYTON,A NEW GENUS OF CORALLINACEAE (CRYPTONEMIALES,RHODOPHYTA) FROM THE SOUTHERN HEMISPHERE1

Synarthrophyton gen. nov. is described based on southern Australian material of Melobesia patena Hooker fils & Harvey, which shows features intermediate between Mesophyllum Lemoine and Lithothamnium Philippi. It has the thin-walled rounded epithallial cells and coaxial hypothallium characteristic of Mesophyllum and the type of procarp and male structures common to Lithothamnium. Synarthrophyton is unique within the subfamily Melobesioideae (J. E. Areschoug) Yendo because it displays secondary pit connections. Details of the vegetative and reproductive morphology of S. patena (Hooker fils. & Harvey) comb. nov. are given and its taxonomic position in the Corallinaceae Lamouroux discussed.     

ROLE OF SURFACE WOUNDS AND BROWN ALGAL EPIPHYTES IN THE COLONIZATION OF ASCOPHYLLUM NODOSUM (PHAEOPHYCEAE) FRONDS BY VERTEBRATA LANOSA (RHODOPHYTA)1

Ascophyllum nodosum (L.) Le Jol. forms extensive beds in wave‐sheltered, rocky intertidal habitats on the northwestern Atlantic coast. This fucoid seaweed is host to an obligate red algal epiphyte, Vertebrata lanosa (L.) T. A. Chr. [=Polysiphonia lanosa (L.) Tandy], and two facultative brown algal epiphytes, Elachista fucicola (Velley) Aresch. and Pylaiella littoralis (L.) Kjellm. Although V. lanosa can occur throughout most of the length of host fronds, it largely predominates in midfrond segments. The two brown algal epiphytes are restricted to distal segments. Through field experiments conducted in Nova Scotia, Canada, we tested the hypothesis that surface wounds are required for the colonization of distal segments of host fronds by V. lanosa. Distal tissues normally have a smooth surface because of their young age (A. nodosum fronds grow apically). By creating small wounds that mimicked grazing wounds distributed elsewhere on host fronds, we demonstrated that V. lanosa can colonize distal frond segments during the growth and reproductive season (summer and autumn). Approximately half of the artificial wounds were colonized by V. lanosa during this time. The experimental exclusion of both brown algal epiphytes from distal frond segments did not affect colonization by V. lanosa. Thus, we conclude that the absence of surface irregularities on distal segments of host fronds, specifically small wounds, is the main factor explaining the absence of V. lanosa there. We propose that further experimental work clarifying epiphyte distribution in host beds will enhance our ability to understand the functional role of epiphytes in intertidal ecosystems.     

CROSSING EXPERIMENTS,LIPID COMPOSITION,AND THE SPECIES CONCEPT IN ECTOCARPUS SILICULOSUS AND E. FASCICULATUS (PHAEOPHYCEAE,ECTOCARPALES)1

Sporophytes of Ectocarpus siliculosus (Dillwyn) Lyngbye and E. fasciculatus Harvey were collected in the vicinity of Roscoff Brittany, France. Gametophytes derived from meiospores were used for intra- and interspecific crosses. Intraspecific gamete combinations gave viable zygotes, which developed into fertile sporophytes. Interspecific crosses were unsuccessful. Gamete fusions did not occur between female gametes of E. fasciculatus and male gametes of E. siliculosus. Hybrid zygotes were formed in the reciprocal combination but died soon after germination. We conclude that the two species of Ectocarpus at Roscoff represent distinct taxonomic entities, which are separated by pre- and postzygotic compatibility barriers. These biological findings are confirmed by the differential occurrence of the chemotaxonomic marker betaine-lipid diacetylglycerylhydroxymethyltrimethyl-β-alanine, which is present in our cultures of E. fasciculatus but absent in E. siliculosus.     

Transfer of a marine DNA virus fromEctocarpus toFeldmannia (Ectocarpales,Phaeophyceae): aberrant symptoms and restitution of the host

Summary The marine brown algaEctocarpus siliculosus is invaded by a polyhedric virus, whose genome consists of circular, double-stranded DNA. In laboratory experiments this virus can infect a different host species,Feldmannia simplex. InfectedFeldmannia plants show severe somatic malformations. However, no functional virus particles are formed. SuchFeldmannia plants recover to resume a normal, symptom-free appearance. This result raises the possibility of intergeneric gene transfer in the natural habitat.     

Comparison of the potential rate of population increase of brown and green color morphs of Sitobion avenae (Homoptera: Aphididae) on barley infected and uninfected with Barley yellow dwarf virus

Life tables of brown and green color morphs of the English grain aphid, Sitobion avenae (Fabricius) reared on barley under laboratory conditions at 20 ± 1°C, 65% ± 5% relative humidity and a photoperiod of 16 : 8 h (L : D) were compared. The plants were either: (i) infected with the Barley yellow dwarf virus (BYDV); (ii) not infected with virus but previously infested with aphids; or (iii) healthy barley plants, which were not previously infested with aphids. Generally, both color morphs of S. avenae performed significantly better when fed on BYDV‐infected plants than on plants that were virus free but had either not been or had been previously infested with aphids. Furthermore, when fed on BYDV‐infected plants, green S. avenae developed significantly faster and had a significantly shorter reproductive period than the brown color morph. There were no significant differences in this respect between the two color morphs of S. avenae when they were reared on virus‐free plants that either had been or not been previously infested with aphids. These results indicate that barley infected with BYDV is a more favorable host plant than uninfected barley for both the color morphs of S. avenae tested, particularly the green color morph.     

Viral inosine triphosphatase: A mysterious enzyme with typical activity,but an atypical function

Plant viruses typically have highly condensed genomes, yet the plant-pathogenic viruses Cassava brown streak virus, Ugandan cassava brown streak virus, and Euphorbia ringspot virus are unusual in encoding an enzyme not yet found in any other virus, the “house-cleaning” enzyme inosine triphosphatase. Inosine triphosphatases (ITPases) are highly conserved enzymes that occur in all kingdoms of life and perform a house-cleaning function by hydrolysing the noncanonical nucleotide inosine triphosphate to inosine monophosphate. The ITPases encoded by cassava brown streak virus and Ugandan cassava brown streak virus have been characterized biochemically and are shown to have typical ITPase activity. However, their biological role in virus infection has yet to be elucidated. Here we review what is known of viral-encoded ITPases and speculate on potential roles in infection with the aim of generating a greater understanding of cassava brown streak viruses, a group of the world's most devastating viruses.     

Undaria mitochondrial large subunit ribosomal DNA (Phaeophyceae, Alariaceae): Structural properties and use for phylogenetic analysis

We sequenced mitochondrial 23S ribosomal DNA (rDNA) from two Undaria species and compared them with homologous sequences from related brown algae. The 23S rDNA sequences from Undaria pinnatifida (Harvey) Suringar were 2707 bp in length, of which 1290–1292 sites were assigned to stem regions and the rest to loop regions in the rRNA secondary structure model. In Undaria undarioides (Yendo) Okamura, the sequences were 2708–2709 bp in length and 1290 sites were assigned to stems. There were three sequence types among the seven U. pinnatifida individuals examined and two among the four U. undarioides individuals. A maximum parsimony analysis of these sequence data with those from related brown algal species resolved a robust monphyly of each of the two Undaria species, suggesting the utilities of 23S rDNA for phylogeny at species or intraspecific level in brown algae. Accounting for variations among sequences parsimoniously, sequence changes were sorted into 423 events, of which 165 were mapped to stems of the secondary structure.     

CULTURE STUDIES ON THE LIFE HISTORY OF CHORDARIA LINEARIS (PHAEOPHYCEAE) FROM TIERRA DEL FUEGO,SOUTH AMERICA1

Studies of laboratory cultures of Chordaria linearis (Hooker et Harvey) Cotton from southernmost South America revealed that this species has an obligate sexual life history in which a macroscopic sporophyte alternates with a monoecious microscopic gametophyte. Sexual reproduction is isogamous and under photoperiodic control. Gametes are produced only in short days, whereas in long days, asexual zoospores are formed that recycle the gametophyte generation. Unfused gametes develop into gametophytes, and sporophytes originate only from zygotes. Unlike other sexual members of the Chordariales, gametes of C. linearis have a reduced stigma and do not show phototaxis. They are released at the beginning of the night, not in the morning. In nature, C. linearis seems to be regularly infected by a dictyosiphonalean epiphyte resembling the rare arctic species Trachynema groenlandicum (Lund) Pedersen. The epiphyte is responsible for previous contradictory results obtained in laboratory cultures of C. linearis. This is the first record of Trachynema in the southern hemisphere.     

A STERILIZATION PROTOCOL FOR THE DICTYOTALES (PHAEOPHYCEAE)1

Following a study on the effect of several physical (brushing and ultrasound) and chemical (antiseptic and antibiotic) treatments on the brown seaweed Stypopodium zonale (Lamoroux) Papenfuss (Dictyotales, Phaeophyceae), bactericidal treatments that were not phytotoxic to the alga were selected. The sterilization protocol consisted of 1) surface brushing of the explants, 2) incubation in the antiseptic betadine (0.50%) for 5 min, and 3) incubation in an antibiotic mixture (650 mg · L^?1 kanamycin, neomycin, and penicillin G) for 48 h. The response of the material to the treatments was assessed by means of an oxygen electrode, and a bacterial test was performed to test bactericidal efficiency. The protocol rendered photosynthetically active axenic explants of S. zonale and other members of the order (e.g. Zonaria tournefortii(Lam.) Montagne).