Estela M. Plastino

Color inheritance, pigment characterization, and growth of a rare light green strain of Gracilaria birdiae (Gracilariales, Rhodophyta)

Gracilaria birdiae Plastino et E.C. Oliveira is an economically important marine red alga exploited for the production of agar in Brazil. A rare light green strain of G. birdiae was found in a natural population, which raised new questions regarding intraspecific variation. Crosses were performed in unialgal cultures to determine the mode of color inheritance of this light green strain. We determined the growth rate and pigment composition of the light green strain and compared it to the wild‐type, red strain. The light green color is stable and showed a recessive nuclear transmission. The light green strain had lower contents of chlorophyll‐a and phycobiliproteins (phycoerythrin, phycocyanin, and allophycocyanin), and grew more slowly than the red strain. This low performance is probably the reason why this mutant, although being stable, is so rare in nature. Nevertheless, it can be useful as a genetic visual marker and to investigate the structure and functioning of the photosynthetic apparatus.

Global environmental changes: setting priorities for Latin American coastal habitats

As the effects of the Global Climate Changes on the costal regions of Central and South Americas advance, there is proportionally little research being made to understand such impacts. This commentary puts forward a series of propositions of strategies to improve performance of Central and South American science and policy making in order to cope with the future impacts of the Global Climate Changes in their coastal habitats.

Gracilaria birdiae (Gracilariales, Rhodophyta), a new species from the tropical South American Atlantic with a terete frond and deep spermatangial conceptacles

Abstract Gracilaria birdiae Plastino & E.C. Oliveira sp. nov. is described from tropical Brazilian waters, on the basis of a critical comparison with several putatively related species. The species is found from the coast of Ceará State (3°S) to Espírito Santo State (20°S). The thallus is terete throughout, reaching about 40 cm long and 2 mm in diameter; the branching is subdichotomous, becoming unilateral in places; the thallus structure is pseudoparenchymatous and microcystidiate, with thick-walled medullary cells interspersed with a few small cells. The spermatangia are distributed in deep, usually confluent conceptacles (‘henriquesiana-type’). A two-celled carpogonial branch, terminated by a short trichogyne, is lodged in a funnel-shaped depression of the thallus surface. Cystocarps are prominent. The carposporophyte has a broad base and is produced from a dissected fusion cell; it is separated from the vegetative medulla by a few layers of small cells. The tetrasporangia are divided cruciately and are scattered over the thallus surface. Populations from the southern and northern limits of distribution, although exhibiting some morphological variability, are nevertheless interfertile, but they are reproductively isolated from the closest and morphologically very similar species, G. caudata, which has a wider distribution in the tropical western Atlantic and Caribbean. The new species has been exploited for decades for agar production.

Crescimento in vitro de linhagens de coloração vermelha e verde clara de Gracilaria birdiae (Gracilariales, Rhodophyta) em dois meios de cultura: análise de diferentes estádios reprodutivos

Gracilaria sp. is one of the main species collected for agar production in Brazil nowadays. The aim of this work was to compare the in vitro growth of different reproductive phases of wild specimens (reddish) and a color strain (light green) of Gracilaria sp., when cultivated in two culture media: Von Stosch and Provasoli. Six strains were selected: reddish (rd) and light green (lg) gametophytes, both female (F) and male (M); reddish tetrasporophytes, but obtained from different crosses, Frd x Mrd and Flg x Mrd. The growth rates, which were analysed for 28 days, were calculated using fresh mass (mGR) and length (lGR). The light green strain showed lower mGR and lGR than the reddish specimens. The growth was satisfatory in both culture media for wild strains. Reddish and light green male gametophytes and reddish tetrasporophytes showed higher mGR and lGR when cultivated in Provasoli. Light green female gametophytes showed similar mGR in both culture media, but the lGR were higher in Von Stosch. The IGR of tetrasporophytes derived from crosses Frd x Mrd were higher than the tetrasporophytes derived from Flg x Mrd.

Life History, Reproduction and Growth of Gracilaria domingensis (Gracilariales, Rhodophyta) from Brazil

Abstract The life history, reproduction and impact of fertilization on growth rate of Gracilaria domingensis (Kützing) Sonder ex Dickie were studied in vitro. The life history is of the Polysiphonia-type, and was completed in six months. Carpospores developed into plants which produced tetraspores in 60 days. The gametophytes originated from the released tetraspores became fertile after 101 days with a sex ratio of 1:1. Spermatangia were found in single deep conceptacles, verrucosa-type, as well as confluent ones, henriquesiana-type. Mature cystocarps have a conspicuous fusion cell and tubular nutritive cells formed from the gonimoblast to both pericarp and cystocarps floor. Non-fertilized female gametophytes showed a higher number of new apices during cultivation. Fertilized female branches grew similarly to the unfertilized branches during the first three weeks, but much slower from that time on. The reproductive cost, expressed as growth differential was around 55% smaller than the control.

The Gracilariaceae Germplasm Bank of the University of São Paulo, Brazil—a DNA barcoding approach

The University of São Paulo Gracilariaceae Germplasm Bank has 50 strains collected mostly in Brazil, but also elsewhere in the world. This bank has been used as a source of material for research developed locally and abroad. With over 200 species, some of which have high economic value, the family Gracilariaceae has been extensively studied. Nonetheless, taxonomic problems still persist by the existence of cryptic species, phenotypic plasticity, and broad geographic distribution. In the case of algae kept in culture for long periods of time, the identification is even more problematic as a consequence of considerable morphological modification. Thus, the use of molecular markers has been shown to be an efficient tool to elucidate taxonomic issues in the group. In this work, we sequenced the 5′-end of the cox1 gene for 41 strains and the universal plastid amplicon (UPA) plastid region for 45 strains, covering all 50 strains in the bank. In addition, the rbcL for representatives of the cox1/UPA clusters was sequenced for 14 strains. The original species identification based on morphology was compared with the molecular data obtained in this work, resulting in the identification of 13 different species. Our analyses indicate that cox1 and UPA are suitable markers for the delineation of species of Gracilariales in the germplasm bank. The addition of DNA barcode tags to the samples in the Gracilariaceae germplasm bank and the molecular identification of the species will make this bank even more useful for future research as the species can be easily traced and confirmed.

Green mutant frequency in natural populations of Gracilaria domingensis (Gracilariales, Rhodophyta) from Brazil

Green, brown and red phenotypes of Gracilaria domingensis have been observed growing side by side in natural populations in the north-east of Brazil. The phycoerythrin phycocyanin ratio of the three colour types increased from green to brown to red phenotypes. The frequency of green mutant individuals was studied during three consecutive years in two natural populations 110 km apart in Ceara State. Brazil. Green variants were found at frequencies of 7% to 19% in both populations showing that the deficiency in phycoerythrin did not strongly affect the fitness of individuals in these sunny intertidal populations. Moreover, the relative stability of the green allele frequency in space and time suggested that the selective pressures are equivalent in the two sites and/or that the two populations are not genetically isolated.

Codominant inheritance of polymorphic color variants of Gracilaria domingensis (Gracilariales, Rhodophyta)

Agar is the most valuable phycocoloid in the world market. Currently, about half of its production is obtained from the red alga Gracilaria (Gracilariales, Rhodophyta). Consequently, this genus has been the subject of many studies worldwide. A common green color variant of G. domingensis (Kutzing) Sonder ex Dickie was found in a natural population on the northeastern coast of Brazil. Crosses were performed to determine the mode of color inheritance. The results can be interpreted as the expression of a pair of codominant alleles, where the green and red phenotypes are homozygous, and the heterozygotes present a brownish color. Heterozygous tetrasporophytes, at least until they are 4-5 cm long, exhibit a parental influence on the female gametophyte, since the reddish-brown or greenish-brown color is dependent on the female parent color (red or green). Mixed reproductive phases, as well as specimens with patches of different colors bearing spermatangia or cystocarps, were observed in laboratory cultures. Gametophytes that resulted from in situ germination of meiospores were also observed, and could be easily detected when red or green gametophytes were grown on brown tetrasporophytes.

Color inheritance and pigment characterization of red (wild-type), greenish-brown, and green strains of Gracilaria birdiae (Gracilariales, Rhodophyta)

Species of Gracilaria are some of the most useful algae in the world for the production of agar. As a consequence of its economic importance, the genus has been the subject of many studies worldwide. Color variants of Gracilaria birdiae have been found in the natural population on the Brazilian coast, and they have also been isolated from plants cultivated in laboratory. These findings raised new questions regarding intraspecific variation and the prospects of cultivating such variants for their agar production. Therefore, this work aimed to determine the mode of color inheritance for two G. birdiae strains: a greenish-brown strain (gb) found in a natural population and a green strain (gr) which had arisen as a spontaneous mutation in a red plant cultured in the laboratory. The pigment contents of these strains, as well as the red wild-type (rd), were also characterized. Crosses between female and male plants of the same color (rd, gr, or gb) and between different colors were performed. Crosses between plants of the same color showed tetrasporophytic and gametophytic descendents of the parental color. Recessive nuclear inheritance was found in the greenish-brown strain, and cytoplasmic maternal inheritance was found in the green strain; both had lower phycoerythrin and higher concentrations of allophycocyanin and phycocyanin than the wild-type. Chlorophyll a contents were similar among all strains. Taken together, our results contribute to knowledge about the variability of this important red algae. In addition, since greenish-brown and green strains showed stability of color, both could be selected and tested in experimental sea cultivation to evaluate if mutants have advantageous performance when compared with red strain.

Deviations in the life-history of Gracilaria sp. (Rhodophyta, Gigartinales), from Coquimbo, Chile, under different culture conditions

Cystocarpic branches of a species of Gracilaria from Coquimbo, Chile, were cultured in vitro. A Polysiphonia-like life history was completed in about 6 months, but some ‘abnormalities’ were observed: i. carpospores gave rise to plants producing either tetrasporangia and spermatangia, or tetrasporangia only; ii. tetraspores cultured without aeration developed into plants bearing spermatangia only; tetraspores cultured with aeration developed into 1:1 female and male gametophytes; iii. plant originated from tetraspore produced spermatangia and tetrasporangia; one of these tetraspores developed into a male gametophyte; iv. some tetraspores gave rise to spherical bodies instead of the ordinary cylindrical branches; one of them bore spermatangia after three months. The results show that environmental factors seem to be interfering with the mechanism of sex determination and induce the development of spermatangia on putative female gametophytes, or on putative tetrasporophytes.