Different Growth and Sporulation Responses to Temperature Gradient among Obligate Apomictic Strains of Ulva prolifera.

The green macroalga Ulva prolifera has a number of variants, some of which are asexual (independent from sexual variants). Although it has been harvested for food, the yield is decreasing. To meet market demand, developing elite cultivars is required. The present study investigated the genetic stability of asexual variants, genotype (hsp90 gene sequences) and phenotype variations across a temperature gradient (10-30 °C) in an apomictic population. Asexual variants were collected from six localities in Japan and were isolated as an unialgal strain. The hsp90 gene sequences of six strains were different and each strain included multiple distinct alleles, suggesting that the strains were diploid and heterozygous. The responses of growth and sporulation versus temperature differed among strains. Differences in thermosensitivity among strains could be interpreted as the result of evolution and processes of adaptation to site-specific environmental conditions. Although carbon content did not differ among strains and cultivation temperatures, nitrogen content tended to increase at higher temperatures and there were differences among strains. A wide variety of asexual variants stably reproducing clonally would be advantageous in selecting elite cultivars for long-term cultivation. Using asexual variants as available resources for elite cultivars provides potential support for increasing the productivity of U. prolifera.

Fourfold daily growth rate in multicellular marine alga Ulva meridionalis.

Microalgae with high growth rates have been considered as promising organisms to replace fossil resources with contemporary primary production as a renewable source. However, their microscopic size makes it hard to be harvested for industrial applications. In this regard, multicellular macroalgae are more suitable for harvesting. Here, we show that Ulva meridionalis has the highest growth rate ever reported for a multicellular autotrophic plant. Contrasted to the known bloom-forming species U. prolifera growing at an approximately two-fold growth rate per day in optimum conditions, U. meridionalis grows at a daily rate of over fourfold. The high growth ability of this multicellular alga would provide the most effective method for CO2 fixation and biomass production.

Glycogen synthase kinase-3ß2 has lower phosphorylation activity to tau than glycogen synthase kinase-3ß1.

Glycogen synthase kinase-3ß (GSK-3ß) is a serine/threonine kinase that phosphorylate protein substrates involved in Alzheimer's disease (AD), such as microtubule-associated protein tau and amyloid precursor protein (APP). GSK-3ß consists of two splice variants; the major short form (GSK-3ß1) distributes in many organs and the minor long form (GSK-3ß2), whose structural difference is the insert of only 13 amino acid residues to the C-terminal side of the catalytic site of GSK-3ß1, is present in central nervous system. However, the physiological significances of the two variants are unclear. Here we examined whether the phosphorylation activities of two variants to tau and APP are different in cells. We found that GSK-3ß2 has lower phosphorylation activity to tau at AD-relevant epitope (Ser396) than GSK-3ß1 in cells, whereas the two variants exhibit equivalent levels of phosphorylation activities to APP. Recombinant GSK-3ß2 has also lower phosphorylation activity to tau than GSK-3ß1 in vitro, although the phosphorylation activities of the two variants to a synthetic peptide substrate pGS-2 are comparable. Furthermore, the deletion of the C-terminal tail (CT) of GSK-3ß2 resulted in considerable reduction of tau phosphorylation activity as compared with GSK-3ß1, suggesting that the lower phosphorylation activity of GSK-3ß2 to tau is attributed to weak interaction with tau through its unique higher-order structure of CT constructed by the 13 amino acids insertion. Such information may provide a clue for understanding of the physiological significance of the two splice variants of GSK-3ß and a new insight into the regulation of tau phosphorylation in central nervous system.