LAUSR

Chemical treatment is a powerful way to induce mutagenesis and has been applied in various studies. Here we describe the isolation of a high-growth-rate mutant Pyropia yezoensis induced by ethyl methane sulfonate (EMS) exposure. The mutation was induced using EMS on the thallus. When the gametophytic blades were treated with 2 mM EMS, a high-growth mutant strain PyE2 was obtained. Physiological and proteomic analysis were conducted to compare this strain with the wild-type (WT). The results demonstrated that the growth rate of mutant strain PyE2 was significantly higher than that of the WT in the laboratory. By measuring the biomass of three generations, it was confirmed that the high growth rate of the mutant strain was maintained. The photochemical efficiency and phycoerythrin content of the mutant strain PyE2 were found to be higher than those of the WT. Analysis of random amplified polymorphic DNA also revealed genetic modifications in the mutant. Extracted proteins from PyE2 grown under culture conditions were separated using two-dimensional gel electrophoresis, and changes in the proteome of the blades were analyzed. Approximately 302 protein species were detected, of which 19 were differentially expressed in the mutant and the WT. These results indicate that the growth rate of PyE2 was increased due to the upregulation of proteins potentially involved in photosynthesis and protein synthesis. The use of mutagenesis methods may help to develop new cultivars useful in the nori industry.