Ethylene, light, and anthocyanin synthesis

Ethylene control of anthocyanin formation functions only through light-initiated synthesis pathways of the rapid synthesis phase. Treatment with ethylene in the dark had no effect on dark anthocyanin synthesis in red cabbage (Brassica oleracea L.). Pretreatment of both red cabbage and sorghum (Sorghum vulgare L.) with ethylene for 24 hours in the dark did increase the rate of synthesis when the tissue was placed in the light. Light-initiated anthocyanin synthesis is inhibited by ethylene when the tissue is returned to the dark.     

Photosynthetic Independence of Light-induced Anthocyanin Formation in Zea Seedlings

Results are reported which support the view that the photosynthetic photosystems are not involved in the high irradiance response (HIR) phenomenon of light-dependent anthocyanin biosynthesis in dark-grown Zea mays L. seedlings. A negative correlation between change in greening rates and change in light-dependent anthocyanin accumulation rates with age was demonstrated. Lack of chlorophyll synthesis in a strain of maize possessing a temperature-sensitive lesion for chlorophyll synthesis could not be correlated with light-induced anthocyanin accumulation. Furthermore, seedlings totally lacking photosynthetic capabilities, either due to a genetic lesion or to excision of all photosynthetic tissue, had an enhanced rate of photoinduced anthocyanin formation. This evidence indicates that the HIR results in the initiation of processes that are in competition with chloroplast development for substrate in normal, intact seedlings.     

Ethylene control of anthocyanin synthesis in sorghum

Light-induced anthocyanin synthesis in Sorghum vulgare L. seedlings was both promoted and inhibited by ethylene treatment. The rate of anthocyanin formation in sorghum tissue was dependent upon the time of ethylene treatment in relation to light exposure and the stage of the anthocyanin synthesis process. Those plants receiving ethylene treatment during the early lag phase of anthocyanin synthesis had higher anthocyanin content at 24 hours than control plants receiving no ethylene treatment. Plants receiving ethylene treatment after the lag phase had lower anthocyanin content at 24 hours than control plants receiving no ethylene treatment.     

Inhibition of ethylene production by rhizobitoxine

Rhizobitoxine, an inhibitor of methionine biosynthesis in Salmonella typhimurium, inhibited ethylene production about 75% in light-grown sorghum seedlings and in senescent apple tissue. Ethylene production stimulated by indoleacetic acid and kinetin in sorghum was similarly inhibited. With both apple and sorghum, the inhibition could only be partially relieved by additions of methionine. A methionine analogue, α-keto-γ-methylthiobutyric acid, which has been suggested as an intermediate between methionine and ethylene, had no effect on the inhibition.     

Role of ethylene in phytochrome-induced anthocyanin synthesis

Summary Synthesis of anthocyanin pigments in etiolated cabbage seedlings is influenced by ethylene at concentrations higher than 10 ppb, and etiolated seedlings produce sufficient ethylene to influence their anthocyanin synthesis. When escape of endogenous ethylene from this tissue is enhanced by means of hypobaric treatment, anthocyanin synthesis is accelerated. Stimulation of anthocyanin synthesis by brief red illumination is completely prevented by applied ethylene and indoleacetic acid inhibits anthocyanin synthesis by stimulating ethylene production. Red light reduces endogenous as well as auxin-induced ethylene production and there is a close correlation between light-induced inhibition of ethylene synthesis and stimulation of anthocyanin formation. We suggest that in part photo-induced anthocyanin synthesis is due to a lowered ethylene content in light-treated tissue.     

The Influence of Auxin and Ethylene on Chromatin-directed Ribonucleic Acid Synthesis in Soybean Hypocotyl

Soybean seedlings treated with ethylene exhibited small increases in ribonucleic acid content in the elongating section of the hypocotyl. Chromatin isolated from the elongating section of ethylene-treated seedlings showed a 35 to 60% increase in the capacity for RNA synthesis. The ethylene-induced response was saturated at 1 microliter/liter of ethylene and was fully expressed after 3 hours. Auxin caused marked accumulation of RNA and DNA in the elongating and basal tissue of the hypocotyl. Chromatin isolated from these auxin-treated tissues showed an 8- to 10- fold increase in RNA synthetic capacity as measured in vitro. Ethylene added with auxin reduced the auxin enhancement of nucleic acid synthesis in the elongating and basal tissues. Both ethylene and auxin treatment of the seedlings inhibited nucleic acid accumulation and chromatin activity in the apical tissue. Ethylene did not appear to mediate the auxin effects on nucleic acid synthesis in soybean hypocotyl with the possible exception of inhibition in the apical tissue.     

Effects of G protein and cGMP on phytochrome-mediated amaranthin synthesis inAmaranthus caudatus seedlings

The effects of G protein and cGMP on phytochrome-mediated amaranthin biosynthesis inAmaranthus caudatus seedlings were studied. It was shown that G protein agonist cholera toxin induced amarathin synthesis in darkness, whereas G protein antagonist pertussis toxin inhibited red light-induced amaranthin synthesis. Amaranthin synthesis was also induced by exogenous cGMP, while the amaranthin biosynthesis induced by cholera toxin, red light and exogenous cGMP was inhibited by genistein. L Y-83583, an inhibitor of guanylyl cyclase, inhibited the amarenthin synthesis induced both by red light and cholera toxin, while it was not able to inhibit the amaranthin synthesis induced by exogenous cGMP. These results suggest that G protein, guanylyl cyclase and cGMP were the candidates in phytochrone signal transduction chain for red light-induced amaranthin biosynthesis and the red light signal transduction chain might be as follows: red light → phytochrome → G protein → guanylyl cyclase → cGMP.     

Biosynthesis of cyanidin in buckwheat hypocotyls

Aminooxyacetate (AOA), an inhibitor of phenylalanine transamination and deamination in vitro, inhibits the light-induced formation of chlorogenic acid, leucoanthocyanin, rutin and anthocyanin (cyanidin glycosides) in buckwheat hypocotyls. Anthocyanin production is inhibited 87 ± 4%, when excised hypocotyls are incubated in 0.5 mM AOA in Petri dishes. AOA is also effective when taken up through the roots or sprayed onto seedlings. In the presence of biosynthetic precursors of cyanidin (l-phenylalanine, trans-cinnamic acid, p-coumaric acid, naringenin, eriodictyol, dihydrokaempferol. and dihydroquercetin) the inhibition of anthocyanin formation caused by AOA is completely or partially reversed. The general applicability of a complementation technique involving AOA or a similar inhibitor of phenylpropane synthesis is proposed to investigate the biosynthesis of natural products derived from cinnamic acid.     

Role of Ethylene in the Germination of the Hemiparasite Striga hermonthica

Seed germination of the hemiparasitic angiosperm Striga hermonthica (Del.) Benth is elicited by compounds present in the root exudates of the host plant. Although a variety of compounds can substitute for the host-derived signal, the mechanism through which these act is unknown. In the present study, an inhibitor of ethylene biosynthesis, aminoethoxyvinyl glycine, was found to inhibit germination. Addition of an intermediate in ethylene biosynthesis, 1-aminocyclopropane-1-carboxylic acid, was found to override this inhibition and to act as a substitute for the host-derived signal. 2,5-Norbornadiene, an inhibitor of ethylene action, was also found to inhibit germination. Ethylene is rapidly produced by Striga seeds after treatment with host root exudates. These results are consistent with a model for Striga seed germination in which host-derived signals and other compounds act by eliciting the synthesis of ethylene and in which ethylene itself initiates the biochemical changes leading to germination.     

Endogenous ethylene production is a potential problem in the measurement of nitrogenase activity associated with excised corn and sorghum roots

Endogenous ethylene production was evaluated as a source of ethylene during acetylene reduction assays with freshly collected roots of field-grown corn, Zea mays L. cv Funks G-4646, and sorghum, Sorghum bicolor (L.) Moench. cv CK-60A. Ethylene production was not detected when roots were incubated in air without acetylene. The presence of endogenous ethylene production was confirmed when roots were incubated anaerobically and in the presence of 40 millimolar sodium hydrosulfite. Ethylene oxidase activity was also associated with excised roots. The rate of ethylene oxidation was higher than the rates of ethylene accumulation during either acetylene reduction assays or anaerobic incubations. These results indicate that the procedure of incubating roots of grasses in air to monitor endogenous ethylene production is not a valid control in acetylene reduction studies with grasses. The presence of endogenous ethylene production during acetylene reduction assays was demonstrated by using either CO to inhibit nitrogenase activity or chloramphenicol to inhibit nitrogenase synthesis in freshly excised roots.     

The FUSCA genes of Arabidopsis: negative regulators of light responses

More than 200 fusca mutants of Arabidopsis have been isolated and characterised, defining 14 complementation groups. Mutations in at least nine FUSCA genes cause light-dependent phenotypic changes in the absence of light: high levels of anthocyanin accumulation in both the embryo and the seedling, inhibition of hypocotyl elongation, apical hook opening, and unfolding of cotyledons. In double mutants, the fusca phenotype is epistatic to the hy phytochromedeficiency phenotype, indicating that the FUSCA genes act downstream of phytochrome. By contrast, the accumulation of anthocyanin is suppressed by mutations in TT and TTG genes, which affect the biosynthesis of anthocyanin, placing the FUSCA genes upstream of those genes. Regardless of the presence or absence of anthocyanin, fusca mutations limit cell expansion and cause seedling lethality. In somatic sectors, mutant fus1 cells are viable; expressing tissue-specific phenotypes: reduced cell expansion and accumulation of anthocyanin in subepidermal tissue, formation of ectopic trichomes but no reduced cell expansion in epidermal tissue. Our results suggest a model of FUSCA gene action in light-induced signal transduction.     

RNA biosynthesis in adipose tissue: effect of fasting

RNA metabolism has been examined in intact adipose tissue and isolated fat cells from rats. The lipocyte contains three species of RNA with sedimentation rates corresponding to those of ribosomal and transfer RNA. The de novo biosynthesis of RNA by adipose tissue cells in vitro was demonstrated. The base ratios of the RNA formed indicate that it was synthesized from a DNA template. Actinomycin D administered in vivo and in vitro decreased total RNA synthesis with the most marked effect on the synthesis of the heavy RNA components. Actinomycin D or puromycin added in vitro was not toxic: they did not inhibit total fatty acid biosynthesis or glucose utilization by the fat pad nor did they inhibit the immediate stimulation of fatty acid biosynthesis and glucose uptake by the addition of insulin in vitro. Starvation for 48-72 hr significantly depressed the synthesis of the heavy RNA components as measured by in vitro uridine incorporation into the individual RNA classes. Refeeding the fasted rat with glucose repaired the defect in RNA biosynthesis before the biosynthesis of monoenoic fatty acid was completely restored. Actinomycin D administered at the time of refeeding prevented the repair of monoenoic fatty acid synthesis. It is concluded that RNA metabolism is intimately involved in the control of biosynthetic reactions in adipose tissue.     

Transcriptome analysis reveals anthocyanin acts as a protectant in <Emphasis Type="Italic">Begonia semperflorens</Emphasis> under low temperature

Anthocyanins are natural bioactive pigments in plants that play important roles in many physiological functions. They are found in various tissues and can protect plants against different stress conditions. Anthocyanins are synthesized and accumulate in nutritional organs, which is crucial for plants to adapt to and resist adverse environmental conditions, including high exposure to light, ultraviolet light, low temperatures, drought, pests and disease. Some progress has been made in understanding the adaptability of anthocyanin to the external environment. Begonia semperflorens is an excellent model for studying the function and regulation of anthocyanin synthesis. To investigate the biosynthesis and regulation of anthocyanins, RNA sequencing techniques were employed to investigate anthocyanin biosynthesis induced by low temperature in B. semperflorens leaves. A total of 74,779 unigenes with a mean length of 1249 bp were assembled. Functional annotations were implemented using five protein databases. Differentially expressed genes involved in the process of anthocyanin biosynthesis were identified. This study represents the first report of a broad-scale gene expression study on B. semperflorens.