Genetic analysis of the period of meiosis and morphogenesis of the gametophytic blades in Pyropia suborbiculata (Bangiales, Rhodophyta)

Abstract

A crossing experiment between two artificial pigmentation mutants of Pyropia suborbiculata (Bangiophyceae, Rhodophyta) was carried out, by which we confirmed when the meiotic phase occurred in its life cycle. Moreover, the early development and morphogenesis of Py. suborbiculata blades were also observed. The red-type pigmentation mutant (HT) was used as the female parent, and the green-type (LT) was used as the male parent. The F1 gametophytic blades developed from conchospores which were released from heterozygous conchocelis showed two parental colors (G and R) and two new colors (W, wild-like color; Y, yellow-brown color). Linear segregation of colors occurred in the F1 blades, forming color-sectored blades with 2–4 sectors. Of the F1 gametophytic blades, 89.2% were color-sectored, and the proportion of two-sectored and three-sectored blades was the highest, accounting for 41.5% and 40%, respectively. Sectors of these four colors appearing in the sectored blades were in a ratio of 1054 R:1030 G:824 W:591 Y, which was approximately 1 R:0.98 G:0.78 W:0.56 Y. These results indicated that the meiosis of Py. suborbiculata occurred during the initial two-cell divisions of the germinating conchospores. Linear tetrad resulted from the meiosis continued to develop, the first vertical division started when the blades were divided into 6–9 cells, and the blade shape began to widen. Afterwards, a large amount of monospores was formed and released from the tip of blades, eventually resulting in round- or kidney-shaped blades in Py. suborbiculata.