植物在进化过程中形成了对环境信号反应的能力，光是植物生长发育中的一个重要的环境信号。植物为了更好地生长和发育形成了精密的光信号接收和转导系统。本文对近年来光信号的接收系统即光受体、光信号的转导研究进展进行了综述。

We investigated the influence of low light intensity on the pigmentation of petals in potted lisianthus [Eustoma grandiflorum (Raf.) Shinn.]. When whole plants were placed under 1,000 lx, the petals at anthesis had lighter petal than control flowers exposed to 10,000 15,000 lx. Shading flower buds during the opening process had no effect on petal color intensity. However, shading the stem and leaf parts significantly reduced the intensity of petal color. When flower buds were detached with peduncles and placed in sucrose solutions, their petal color became more intense as the sucrose concentration was increased. There was a positive correlation between anthocyanin and soluble sugar content in the petals, regardless of light conditions. In detached flowers, the transcript levels of chalcone synthase, chalcone isomerase, and dihydroflavonol 4 reductase were enhanced as the sucrose concentration increased. These results suggest that low light intensity affects petal pigmentation through reduced photosynthesis in the leaves or stems, which, in turn, reduces the soluble sugar content of petals and leads to a repression of the genes that encode enzymes of anthocyanin biosynthetic pathway.

The expression of anthocyanin biosynthesis pathway genes was investigated in 'Nyoho' strawberry fruits during fruit development. Fruit color changed from pale-green to white about 3 weeks after anthesis (white-mature stage). At this stage, anthocyanins rapidly accumulated until the full ripe. Total soluble sugar content also increased after white-mature stage. This includes sucrose but not glucose and fructose levels that remained constant during ripening. The transcript level of phenylalanine ammonialyase (PAL) and chalcone synthase (CHS) genes did not change markedly throughout the fruit development. The transcript level of chalcone isomerase (CHI) and dihydroflavonol 4-reductase (DFR) gene was high in the young fruit, decreased to an almost undetectable level at the white-mature stage, and then increased again until the fully ripe stage paralleling mostly the accumulation of anthocyanin. The latter corelation suggests the involvement of CHI and DFR in the regulation of anthocyanin biosynthesis during fruit ripening.

Low light intensity causes poor flower pigmentation possibly by two mechanisms: 1) the reaction mediated by photoreceptors located in the petal, 2) the reaction mediated by the sugar supply from leaves or stems. We investigated which mechanism is more important in the pigmentation of the oriental hybrid lily, 'Acapulco' and stock, 'Pigmy Rose'. Shading flowers by cheesecloth (PPFD<17umo\om～2osec1) or by aluminum foil (0umo\om～2osec1) reduced anthocyanin concentration in both species, suggesting that anthocyanin production is a photoreceptor-mediated reaction. When whole plants were shaded by cheesecloth (<17umolom～2osec1) in lily, anthocyanin concentration became lower than that of flower-shaded plants. This treatment reduced total sugar concentration from 3% to 1.6%, suggesting that limited sugar supply caused poor anthocyanin production in lily. In contrast, in stock, whole plant shading did not reduce anthocyanin concentration as compared with flower-shaded plants, suggesting that the amount of available sugar is not a limiting factor for anthocyanin production. Although this treatment reduced total sugar concentration from 4.7% to 3.7%, it was still higher than that of the control l i ly plants. When detached florets of stock were placed on sucrose solutions, the anthocyanin concentration declined as hexose concentration in the petal decreased, especially under 2%. These results indicate that, although soluble sugars in petals affected anthocyanin production, their high concentration prevented fading of flower color, even under low light conditions in stock.

The rice pyruvate decarboxylase 3 gene (PDC3), which has no introns, was previously postulated to be a pseudogene because no PDC3 mRNA had been detected, even under anaerobic conditions. However, in this study, it was found that rice PDC3 transcripts accumulated in panicles after heading. Within anthers obtained from the panicles, PDC3 was shown to be transcribed in mature pollen by in situ hybridization. These results suggest that the rice PDC3 is a functional gene. Its product may play a role in aerobic alcoholic fermentation in mature pollen.