Hitoshi Yasuda

Occurrence of anthocyanoplasts in cell suspension cultures of sweet potato.

Intensely pigmented and spherical vesicles (anthocyanoplasts) were found in anthocyanin-containing cells of sweet potato (Ipomoea batatas) suspension cultures. Anthocyanin synthesis began to first occur 24–48 h after exposure to light, and then numerous small red vesicles were detected under a microscope. The frequency of anthocyanoplast-containing cells rapidly increased to finally about 80% of the total cultured cells after 5 days of irradiation. Fully developed anthocyanoplasts reached 10–15 μm in diameter. On the other hand, neither anthocyanin synthesis nor development of anthocyanoplasts was induced in the dark-cultured cells. 2,4-D also inhibited anthocyanin synthesis and development of these vesicles. The results suggest that anthocyanoplasts might be a site of anthocyanin synthesis and/or accumulation.

Expression Pattern and Gene Structure of Phenylalanine Ammonia-Lyase in Pharbitis nil

PAL gene expression were examined in flower buds and irradiated hypocotyls in Pharbitis nil. PAL activity and transcript levels were correlated with the accumulation of anthocyanin. Both in flower buds and hypocotyls, transcript levels, PAL activity, and then the amount of anthocyanin, increased. The PAL transcript was abundant in flower buds for a few days before flower opening. But the increase in PAL transcript induced by irradiation was temporal in hypocotyls. Phytochrome was shown to be involved in inducing the accumulation of anthocyanin in hypocotyls. To examine the mechanism regulating the expression of the PAL gene, the gene was cloned and sequenced, and the promoter region was compared with that of other PALs. The gene had two exons separated by an intron of 989 bp with consensus sequences at the intron/exon border. The predicted primary structure of the PAL protein consists of 711 amino acids. The promoter region was AT-rich and there were sequences similar to box 1, box 2, an AT-1 binding site and a G box. The role of PAL in the accumulation of anthocyanin is discussed.

Effects of Temperature on the Pattern of Anthocyanin Accumulation in Seedlings of Polygonum cuspidatum

Polygonum cuspidatum seedling. Anthocyanin accumulated first in the lower part of hypocotyls and then the site of accumulation gradually extended toward the upper part of hypocotyls when seedlings were irradiated with white light (WL) at 25 C. Etiolated seedlings accumulated anthocyanin only in the upper parts (hook and cotyledons) when the seedlings were irradiated with WL at 5 C. De-etiolated seedlings that had been pre-irradiated with WL for 1 day at 25 C accumulated anthocyanin both in upper and lower parts of the seedlings when the seedlings were irradiated with WL at 5 C. Spectral sensitivity was dependent on the temperature during irradiation. Red light (R), blue light (B), and near ultra-violet light (NUV) induced the accumulation of anthocyanin at 5 C but only NUV was effective in inducing the accumulation of anthocyanin at 25 C. Dichlorophenyl dimethylurea (DCMU) inhibited WL-induced anthocyanin accumulation but did not NUV-induced anthocyanin accumulation at 25 C. However, sucrose promoted NUV action at 25 C, indicating that photosynthesis can promote NUV-induced anthocyanin accumulation. Distribution of phytochrome in etiolated seedlings, that was examined by spectrophotometry, was similar to the distribution of anthocyanin at 5 C. Furthermore, phytochrome remained after 48 hr irradiation with WL at 5 C although phytochrome was rapidly degraded at 25 C.