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.

Evaluation of a new experimental kit for the extraction of DNA from bones and teeth using a non-powder method.

An experimental DNA extraction kit (new kit) was recently developed to extract DNA from degraded skeletal remains without the need for powdering the samples. We compared the utility of the new kit with the conventional phenol/chloroform method using real-time quantitative PCR and multiplex STR analysis. The new kit yielded large amounts of DNA from a compact bone fragment compared with the conventional phenol/chloroform method. We were able to extract sufficient DNA for STR analysis from 75% (3 of 4) and 60% (3 of 5) of the un-powdered tooth and bone samples, respectively, using the new kit. We were able to perform mini-STR analysis of the remaining samples using DNA extracted with the new kit. Furthermore, we successfully performed mitochondrial DNA sequencing of every sample. The new kit simplifies the DNA extraction procedure as it does not require powdering samples. Decreasing the number of procedural steps in DNA extraction will be beneficial in controlling DNA contamination in laboratories. Our results suggest that the new kit may be used for the simple, simultaneous extraction of DNA from multiple samples.