Molecular support for the establishment of the new genus Laurenciella within the Laurencia complex (Ceramiales, Rhodophyta)

Currently, five genera are assigned to red seaweeds of the Laurencia complex worldwide: Chondrophycus, Laurencia s.s., Osmundea, Palisada and Yuzurua. The genera are segregated on the basis of morphological characters, especially the reproductive traits, and molecular sequences of the plastid-encoded gene rbcL. Four of the genera have been resolved as monophyletic, but not Laurencia s.s. In this study based on an rbcL gene phylogeny we show the presence of a sixth lineage within the Laurencia complex, viz., Laurencia marilzae plus two unidentified species of Laurencia from Brazil. The phylogenetic position of this group, combined with the high genetic divergence from Laurencia s.s. (8.2-11%), strongly support the establishment of a sixth genus for the complex, proposed here as Laurenciella gen. nov. This new taxon differs from Laurencia s.s. and from the other genera of the complex by molecular sequence data, but is indistinguishable from Laurencia s.s. by the usual morphological features.

Redefining the taxonomic status of Laurencia dendroidea (Ceramiales, Rhodophyta) from Brazil and the Canary Islands

Morphological and molecular studies have been performed on Laurencia dendroidea derived from Brazil and the Canary Islands. This species possesses all of the characters that are typical of the genus Laurencia, including the production of the first pericentral cell underneath the basal cell of the trichoblast; the production of tetrasporangia from particular pericentral cells without the formation of additional fertile pericentral cells; spermatangial branches that are produced from one of two laterals on the suprabasal cell of the trichoblasts; and a procarp-bearing segment that possesses five pericentral cells. The phylogenetic position of L. dendroidea was inferred by analysing the chloroplast-encoded rbcL gene sequences of 51 taxa. Phylogenetic analyses revealed that the taxa previously identified and cited in Brazil as Laurencia filiformis, L. majuscula and L. obtusa and in the Canary Islands as L. majuscula all represent the same taxonomic entity and examination of type material allowed us to identify this entity as L. dendroidea, whose type locality is in Brazil. Laurencia obtusa from the Northern Atlantic is confirmed to represent a distinct species, which displays high genetic divergence with respect to western and eastern Atlantic samples. The phylogenetic analyses also supported the nomenclatural transfer of Chondrophycus furcatus (Cordeiro-Marino & M. T. Fujii) M. T. Fujii & Senties to Palisada furcata (Cordeiro-Marino & M. T. Fujii) Cassano & M. T. Fujii comb. nov.

Morphological and molecular evidence demonstrates the amphi-Atlantic distribution of Laurencia catarinensis (Ceramiales, Rhodophyta)

We performed morphological and molecular studies of Laurencia catarinensis from the Canary Islands. This species has an entangled habit, cushion-like tuft formation, cortical cell walls, slightly to markedly projecting near the apex, and lacking lenticular thickenings in medullary cells. We inferred its phylogenetic position by analyzing the chloroplast-encoded rbcL gene sequences from 41 samples. The results demonstrate that specimens of L. catarinensis from the Canary Islands, where it is referred to as L. intricata, and those from Brazil (including specimens from the type locality in Santa Catarina) form a monophyletic clade with low genetic divergence (0-0.9%). In contrast, specimens of L. intricata from the type locality in Cuba, Mexico, and the USA were clearly distinct from L. catarinensis collected in Brazil and the Canary Islands, as shown by high genetic divergence values (4.9-5.7%). The type material of L. catarinensis from Brazil allowed us to identify all samples from the Canarian Archipelago as L. catarinensis. These findings expand the known geographical distribution of L. catarinensis to the eastern Atlantic Ocean and demonstrate an amphi-Atlantic distribution of the species.

Distribution of the CCR5delta32 allele (gene variant CCR5) in Rondonia, Western Amazonian region, Brazil

Since around 1723, on the occasion of its initial colonization by Europeans, Rondonia has received successive waves of immigrants. This has been further swelled by individuals from northeastern Brazil, who began entering at the beginning of the twentieth century. The ethnic composition varies across the state according to the various sites of settlement of each wave of immigrants. We analyzed the frequency of the CCR5 Delta 32 allele of the CCR5 chemokine receptor, which is considered a Caucasian marker, in five sample sets from the population. Four were collected in Porto Velho, the state capital and the site of several waves of migration. Of these, two, from the Hospital de Base were comprised of HB Mothers and HB Newborns presenting allele frequencies of 3.5% and 3.1%, respectively, a third from the peri-urban neighborhoods of Candelaria/Bate-Estaca (1.8%), whereas a fourth, from the Research Center on Tropical Medicine/CEPEM (0.6%), was composed of malaria patients under treament. The fifth sample (3.4%) came from the inland Quilombola village of Pedras Negras. Two homozygous individuals (CCR5 Delta 32/CCR5 Delta 32) were detected among the HB Mother samples. The frequency of this allele was heterogeneous and higher where the European inflow was more pronounced. The presence of the allele in Pedras Negras revealed European miscegenation in a community largely comprising Quilombolas.

Comparative analysis of the corps en cerise in several species of Laurencia (Ceramiales, Rhodophyta) from the Atlantic Ocean

Different species of Laurencia have proven to be a rich source of natural products yielding interesting bioactive halogenated secondary metabolites, such as terpenoids and acetogenins. It is shown that such compounds are accumulated in the spherical, reniform to claviform refractive inclusions called corps en cerise (CC), which are intensively osmiophilic and located mainly in the cortical cells of the thalli and also in trichoblast cells. Up to now, it was believed that CC were present only in these two kinds of cells. Recently, however, a species of Laurencia, L. marilzae, with CC in all cells of the thallus, i.e., cortical, medullary, including the pericentral and axial cells, as well as in the trichoblasts, was described from the Canary Islands, and subsequently also reported to Brazil and Mexico. Within the Laurencia complex, only Laurencia species produce CC. Since the species of Laurencia are targets of interest for the prospection of bioactive substances due to their potential antibacterial, antifungal, anticholinesterasic, antileishmanial, cytotoxic, and antioxidant activities, the present paper carries out a comparative analysis of the corps en cerise in several species of Laurencia from the Atlantic Ocean to obtain basic information that can support natural product bioprospection projects. Our results show that the number and size of the CC are constant within a species, independent of the geographical distribution, corroborating their use for taxonomical purposes to differentiate groups of species that present a lower number from those that have a higher number. In this regard, there was a tendency for the number of CC to be higher in some species of Laurencia from the Canary Islands. The presence of CC can also be used to distinguish species in which these organelles are present in all cells of the thallus from those in which CC are restricted to the cortical cells. Among the species analyzed, L. viridis displayed the most varied secondary metabolites composition, such as sesquiterpenes, diterpenes, triterpenes, all of which showed potent antiviral, cytotoxic, and antitumoral activities, including protein phosphatase type 2A (PP2A) inhibitory effects.

Morphological and molecular studies on the Brazilian native red seaweed Laurencia oliveirana (Rhodomelaceae, Ceramiales)

Morphological and molecular studies were carried out on Laurencia oliveirana from the type locality (Arraial do Cabo, Rio de Janeiro, Brazil). This species is easily recognized by its small size, sub-erect habit forming intricate cushion-like tufts and unilateral pectinate branching. The species displays all the typical characters of the genus Laurencia, such as the production of the first pericentral cell underneath the basal cell of the trichoblast, tetrasporangia produced from particular pericentral cells, with the third and fourth pericentral cells becoming fertile, without production of additional pericentral cells, spermatangial branches produced from one of two laterals on the suprabasal cell of trichoblasts, and procarp-bearing segment with five pericentral cells. Details of tetrasporangial plants and development of procarp and male plants are described for the first time for the species. The phylogenetic position of L. oliveirana was inferred by analysis of the chloroplast-encoded rbcL gene sequences from 57 taxa. In all phylogenetic analyses, L. oliveirana grouped with L. caraibica, L. caduciramulosa, L. venusta and L. natalensis, forming a monophyletic clade within the Laurencia sensu stricto. The genetic divergence between L. oliveirana and the molecularly closest species, L. caraiba collected in Brazil, was 2.3%.