lyc1, a transgenic mutant of Lactuca sativa (lettuce) tightly linked to chloroplast biogenesis

A T-DNA tagging mutant of lettuce was studied. The transgenic lettuce mutant, designated light yellowish cotyledon1 (lyc1), exhibited a chloroplast mutant phenotype in which the chloroplast development was arrested at the cotyledon stage and the cotyledon became a light yellowish due to the reduced level of chlorophyll content. A microscopic observation of the mutant showed that the chloroplasts failed to position along the cell wall, but were scattered in the cytoplasm. The number of chloroplasts in the mutant was reduced to 66% compared to that in the wild-type plant. These results suggest that the lyc1 mutation is due to a defect in the biogenesis of chloroplasts. Also, the homozygous lyc1 mutant became lethal in a T2 and F1 progeny analysis, indicating that the mutation is recessive.