The first symbiont-free genome sequence of marine red alga, Susabi-nori (Pyropia yezoensis).

Nori, a marine red alga, is one of the most profitable mariculture crops in the world. However, the biological properties of this macroalga are poorly understood at the molecular level. In this study, we determined the draft genome sequence of susabi-nori (Pyropia yezoensis) using next-generation sequencing platforms. For sequencing, thalli of P. yezoensis were washed to remove bacteria attached on the cell surface and enzymatically prepared as purified protoplasts. The assembled contig size of the P. yezoensis nuclear genome was approximately 43 megabases (Mb), which is an order of magnitude smaller than the previously estimated genome size. A total of 10,327 gene models were predicted and about 60% of the genes validated lack introns and the other genes have shorter introns compared to large-genome algae, which is consistent with the compact size of the P. yezoensis genome. A sequence homology search showed that 3,611 genes (35%) are functionally unknown and only 2,069 gene groups are in common with those of the unicellular red alga, Cyanidioschyzon merolae. As color trait determinants of red algae, light-harvesting genes involved in the phycobilisome were predicted from the P. yezoensis nuclear genome. In particular, we found a second homolog of phycobilisome-degradation gene, which is usually chloroplast-encoded, possibly providing a novel target for color fading of susabi-nori in aquaculture. These findings shed light on unexplained features of macroalgal genes and genomes, and suggest that the genome of P. yezoensis is a promising model genome of marine red algae.

Carp (Cyprinus carpio) vitellogenin: characterization of yolk proteins, development of immunoassays and use as biomarker of exposure to environmental estrogens.

The precursor protein of egg yolk, vitellogenin (Vg), is cleaved into three major components (lipovitellin, phosvitin and beta'-component) at the time of incorporation by growing oocytes. We purified three yolk proteins (YP1, YP2 and YP3) from ovaries of the common carp (Cyprinus carpio) by a combined method of ammonium sulfate precipitation and column chromatography. Biochemical analyses of the purified proteins of this species suggest that YP1, YP2 and YP3 are lipovitellin, beta'-component and phosvitin, respectively. A specific antiserum against purified carp YP1 (lipovitellin) was used to develop a single radial immunodiffusion (SRID) technique and an enzyme-linked immunosorbent assay (ELISA) for carp Vg. By SRID and ELISA, we measured the circulating carp Vg level to be in the ranges of 12.5-400 microg/ml and 2.0-1000 ng/ml, respectively, which cover a wide range of Vg levels. From 1997-1998, male and female carp were captured at points of effluent discharge from a sewage treatment plant connected to the Tama River, where estrogenic compounds were later detected, and the presence of Vg in their circulation was examined. Vg was detected in both male and female carp at the mg/ml level, suggesting that estrogens such as estrone and estradiol were sufficiently high to induce Vg in male carp inhabiting this area. The result of this study supports the use of carp Vg as a biomarker of fish exposure to environmental estrogens.