Induction and characterization of pigmentation mutants in Porphyra yezoensis (Bangiales, Rhodophyta)

Porphyra yezoensis Ueda conchospore germlings (1-4-cell stages) were treate d with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for inducing mutations. Three kinds of color-mutated gametophytic blades, which were composed of th e mutated cells wholly, sectorially or spottedly, were obtained; and most o f them were sectorially variegated blades. The highest frequency of these m utated blades was 1.3%. Four different pigmentation mutant strains were obt ained by regenerating single cells and protoplasts that were enzymatically isolated from the mutated sectors of the sectorially variegated blades. The mutants were relatively stable in color in both gametophytic blade and con chocelis phases. In the two phases, each mutant strain showed characteristi c differences in the in vivo absorption spectra, and had different pigment contents of major photosynthetic pigments (chlorophyll a, phycoerythrin and phycocyanin) as compared with the wild-type and with each other. The gamet ophytic blades from the four mutant lines showed significant differences in growth and photosynthetic rates, when they were cultured in the same condi tions. By crossing the mutant with the wild-type, it was found that the col or phenotypes of two mutants reported above, were resulted from two mutatio ns in different genes, respectively.