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The marine red alga Porphyra umbilicalis has high tolerance toward various abiotic stresses. In this study, the contents of floridoside, isofloridoside, and trehalose were measured using gas chromatography mass spectrometry (GC‐MS) in response to desiccation and rehydration treatments; these conditions are similar to the tidal cycles that P. umbilicalis experiences in its natural habitats. The GC‐MS analysis showed that the concentration of floridoside and isofloridoside did not change in response to desiccation as expected of compatible solutes. Genes involved in the synthesis of (iso)floridoside and trehalose were identified from the recently completed Porphyra genome, including four putative trehalose‐6‐phosphate synthase (TPS) genes, two putative trehalose‐6‐phosphate phosphatase (TPP) genes, and one putative trehalose synthase/amylase (TreS) gene. Based on the phylogenetic, conserved domain, and gene expression analyses, it is suggested that the Pum4785 and Pum5014 genes are related to floridoside and isofloridoside synthesis, respectively, and that the Pum4637 gene is probably involved in trehalose synthesis. Our study verifies the occurrences of nanomolar concentrations trehalose in P. umbilicalis for the first time and identifies additional genes possibly encoding trehalose phosphate synthases. [ABSTRACT FROM AUTHOR]

The intertidal marine red alga Porphyra umbilicalis reproduces asexually in the Northwest Atlantic. We looked for population substructure among typical opencoastal and atypical estuarine habitats in seven asexual populations of P. umbilicalis from Maine to New Hampshire using eight expressed sequence tag-simple sequence repeats (EST-SSR) or microsatellite loci. Six genotypes were identified, four of which may represent recombinant genotypes from a recombination event that took place locally, or that took place prior to introduction to the Northwest Atlantic. Genotypic diversity was lowest in a population from Wiscasset, Maine, which inhabits an atypical habitat high in the intertidal zone of a bridge piling in an estuarine tidal rapid. Genotypic diversity was highest in the southernmost populations from New Hampshire; we identified two genotypes that were unique to the southernmost populations, and probably represent the most derived genotypes. We looked at genetic distances among populations in similar habitats, and found that populations were more closely related to their closest neighboring population than to a population in a similar habitat. We show that genotypic diversity within P. umbilicalis populations in the Gulf of Maine is relatively high and thus fits a model of high steady-state variation within asexual populations. [ABSTRACT FROM AUTHOR]

Membrane transporters play a central role in many cellular processes that rely on the movement of ions and organic molecules between the environment and the cell, and between cellular compartments. Transporters have been well characterized in plants and green algae, but little is known about transporters or their evolutionary histories in the red algae. Here we examined 482 expressed sequence tag contigs that encode putative membrane transporters in the economically important red seaweed Porphyra (Bangiophyceae, Rhodophyta). These contigs are part of a comprehensive transcriptome dataset from Porphyra umbilicalis and Porphyra purpurea. Using phylogenomics, we identified 30 trees that support the expected monophyly of red and green algae/plants (i.e. the Plantae hypothesis) and 19 expressed sequence tag contigs that show evidence of endosymbiotic/horizontal gene transfer involving stramenopiles. The majority (77%) of analyzed contigs encode transporters with unresolved phylogenies, demonstrating the difficulty in resolving the evolutionary history of genes. We observed molecular features of many sodium-coupled transport systems in marine algae, and the potential for coregulation of Porphyra transporter genes that are associated with fatty acid biosynthesis and intracellular lipid trafficking. Although both the tissue-specific and subcellular locations of the encoded proteins require further investigation, our study provides red algal gene candidates associated with transport functions and novel insights into the biology and evolution of these transporters. [ABSTRACT FROM AUTHOR]

Information about past periods of climate change can provide a framework for investigating how marine communities may have adapted to changes both geographically and ecologically. The spatial distribution of variable haplotypes from the nuclear ribosomal DNA internal transcribed spacer (ITS1-5.8S-ITS2) region and a ribosomal DNA group-I intron from the obligate, rocky shore intertidal red alga Porphyra umbilicalis were used to reconstruct its biogeographical history since the last glacial maximum in the North Atlantic. Haplotype distributions from European and North American samples representing the range of P. umbilicalis are consistent with the hypothesis that North American populations were extirpated during the last glacial maximum and subsequently recolonized from European donor populations. A non-coding intergenic region between the mitochondrial cytochrome oxidase ( cox)2 and cox3 genes was also investigated, but because there were extremely low levels of intraspecific variation, the spacer was not useful for phylogeographical analysis. [ABSTRACT FROM AUTHOR]

Within the Bangialean red algae the multi-copy small subunit nuclear ribosomal gene (SSU) has been shown to contain group-I introns at positions corresponding to 516 and 1506. Using the polymerase chain reaction (PCR) with primers flanking the 1506 intron we found that this intron was present in some copies of the rDNA in several North Atlantic Porphyra species. However, when the combination of a flanking and internal primer was used to amplify across the intron the percentages of individuals containing the intron increased. The likely explanation for these results was that, when flanking primers were used for PCR, template competition favoured the amplification of the intronless rDNA fragments. A combination of internal and flanking primers used to screen for the 516 intron amplified the intron in every accession of five taxa (Porphyra dioica, P. leucosticta, P. suborbiculata, P. umbilicalis and P. yezoensis) and in most samples of P. amplissima, P. linearis, and P. purpurea. When PCR primers were optimized for the 1506 intron and SSU of P. umbilicalis, the intron was detected in 28/28 samples. Such observations suggest that the 1506 intron is ubiquitous in Porphyra and is present in some, but not all, copies of the ribosomal DNA (rDNA) repeat. Multiple size 1506 introns were detected in individuals of P. umbilicalis. Four of the larger size variants were shown to encode a putative His-Cys box that was associated with mobility of other group-I introns. Our observations suggest that the 1506 group-I intron may still be mobile within the Porphyra lineage. [ABSTRACT FROM AUTHOR]

Dwarf embedded Fucus populations in the Northwest Atlantic Ocean are restricted to the upper intertidal zone in sandy salt marsh environments; they lack holdfasts and are from attached parental populations of F. spiralis or F. spiralis× F. vesiculosus hybrids after breakage and entanglement with halophytic marsh grasses. Dwarf forms are dichotomously branched, flat, and have a mean overall length and width of 20.3 and 1.3 mm, respectively. Thus, they are longer than Irish (mean 9.3 mm) and Alaskan (mean 15.0 mm) populations identified as F. cottonii. Reciprocal transplants of different Fucus taxa in a Maine salt marsh confirm that F. spiralis can become transformed into dwarf embedded thalli within the high intertidal zone, while the latter can grow into F. s. ecad lutarius within the mid intertidal zone. Thus, vertical transplantation can modify fucoid morphology and result in varying ecads. Microsatellite markers indicate that attached F. spiralis and F. vesiculosus are genetically distinct, while dwarf forms may arise via hybridization between the two taxa. The ratio of intermediate to species-specific-genotypes decreased with larger thalli. Also, F. s. ecad lutarius consists of a mixture of intermediate and “pure” genotypes, while dwarf thalli show a greater frequency of hybrids. [ABSTRACT FROM AUTHOR]

The high degree of morphological plasticity displayed by species of the brown algal genusFucusL. is well documented. Such variation is especially pronounced for those estuarine taxa lacking holdfasts (termed ecads) that often bear little resemblance to the attached species from which they are derived. To better understand the systematics of salt marsh fucoids, we developed a suite of four microsatellite-containing loci capable of distinguishing betweenF. vesiculosusL. andF. spiralisL. The genetic markers were used to determine the relationships of the fucoid ecadsF. vesiculosusecadvolubilis(Hudson) Turner and a muscoides-likeFucusin the Brave Boat Harbor (ME, USA) estuary. Ecad populations had 2- to 3-fold higher levels of heterozygosity than attached populations ofF. vesiculosusandF. spiralis. Further, ecads were“intermediate” betweenF. vesiculosusandF. spiralisin their allele frequencies and genotype composition. Our data indicate that populations of muscoides-likeFucusin Brave Boat Harbor mainly consist of F1 hybrids betweenF. vesiculosusandF. spiralis, whereasF. vesiculosusecadvolubilismay arise through backcrosses betweenF. vesiculosusand other fertile hybrids. Finally, our data support the hypothesis that introgression has occurred between attached populations ofF. vesiculosusandF. spiralis. [ABSTRACT FROM AUTHOR]

The article presents a response by Aaron L. Wallace and colleagues to a letter to the editor about their article "Genetic entities and mating systems in hermaphroditic Fucus spiralis and its close dioecious relative F. vasiculosus (Fucaceae, Phaeophyceae), that was published in a 2005 issue of the periodical "Molecular Biology."