Photocontrol of anthocyanin formation in turnip seedlings

Summary The substitution of red or blue light for the first six hours of prolonged irradiation with far-red light reduced anthocyanin formation by about 60%; red or far-red light similarly substituted for blue light had little effect. It is concluded that the effects of prolonged irradiation with blue and far-red depend, in part at least, on different photoreceptors.The effects of pre-treatment with red or blue light also occurred when only short exposures to light were given, and were reversed by immediate brief exposures to far-red. The depressing effect of a short pre-irradiation treatment was largely prevented if seedlings were kept at low temperature or in an atmosphere of nitrogen in the dark period before transfer to the prolonged far-red treatment. The effect of the pre-irradiation treatment is attributed to enzymatic destruction of phytochrome following conversion to the P_FR form, and it is suggested that anthocyanin synthesis in far-red light largely depends on phytochrome, possibly due to the maintenance of a low level of P_FR in the tissue by the absorption tail of P_R in the far-red.A pre-irradiation treatment with red also decreased the inhibitory effect of far-red on hypocotyl elongation but did not change the response to blue light.

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Zusammenfassung Die Anthocyanbildung war im langfristig gegebenen Dunkelrot bis zu etwa 60% reduziert, wenn die ersten 6 Std durch hellrote oder blaue Bestrahlung ersetzt wurden; Hellrot oder Dunkelrot in gleicher Weise im Dauerblaulicht substituiert waren praktisch wirkungslos. Daraus wird geschlossen, daß der Effekt einer Dauerbestrahlung mit Blau und Dunkelrot zum Teil jedenfalls, auf verschiedene Photorezeptoren zurückzuführen ist.Der Effekt einer Vorbehandlung mit hellrotem oder blauem Licht trat auch dann auf, wenn nur kurzfristige Bestrahlungen gegeben wurden und konnte durch unmittelbar nachfolgende kurze Dunkelrot-Belichtung wieder aufgehoben werden. Die Hemmung durch kurzfristige Vorbestrahlung konnte weitgehend verhindert werden, wenn die Keimlinge während der Dunkelperiode, vor der Übertragung in Dauerdunkelrot, bei tiefer Temperatur oder unter Stickstoff gehalten wurden. Der Vorbelichtungseffekt wird auf die enzymatische Destruktion von Phytochrom, nach der Umwandlung in die P_FR-Form, zurückgeführt und es wird vermutet, daß die Anthocyansynthese im Dauerdunkelrot weitgehend phytochromabhängig ist, wahrscheinlich durch die Aufrechterhaltung eines niedrigen P_FR Niveaus im Gewebe infolge der schwachen Absorption von P_R im Dunkelrot.Eine Vorbelichtung mit Hellrot verringerte ebenfalls die hemmende Wirkung von Dunkelrot auf das Hypokotylwachstum, war jedoch ohne Einfluß im Blaulicht.

     

Photocontrol of anthocyanin formation in turnip seedlings

Summary When irradiated for a period of 48 hours with light of restricted wave-lengths in the red and far-red regions, maximum anthocyanin content in hypocotyls was found at 730 nm; in cotyledons the yield at 716 was almost equal to that at 730 nm.In hypocotyls the effectiveness of 703, 716 and 760 nm light was much increased if plants were transferred to red light after 6 hours. The intermediate wave-length band centred at 703 nm was ineffective when given alone but led to a high yield if followed by red light. When given before far-red light (standard far-red field), 6 hours at 703 nm reduced anthocyanin yield in the same way as red light; when given after 6 hours of far-red, however, 703 nm light did not act like red light to sustain a high rate of anthocyanin synthesis.It is concluded that two reactions are involved in the photocontrol of anthocyanin formation in turnip seedlings.     

Contributions of photosynthesis and phytochrome to the formation of anthocyanin in turnip seedlings

Turnip seedlings (Brassica rapa L.) irradiated for 24 hours with radiation at 720 nanometers synthesize chlorophyll a and anthocyanin. Antimycin A and 2,4-dinitrophenol, which are known to reduce cyclic photophosphorylation, also reduce anthocyanin synthesis. Noncyclic photophosphorylation is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and o-phenanthroline. These compounds promote cyclic photophosphorylation and anthocyanin synthesis. On the basis of these findings it is suggested that the photomorphogenic response of anthocyanin synthesis in turnip seedlings arises in part through photosynthetic activity.     

Photocontrol of anthocyanin synthesis: I. Action of short, prolonged, and intermittent irradiations on the formation of anthocyanins in cabbage, mustard, and turnip seedlings

Red far red reversibility (phytochrome control) of anthocyanin synthesis can be easily demonstrated for the response induced by short (5 minutes) and relatively short (4 hours) irradiation. Red far red reversibility of the response induced by longer irradiations can be demonstrated by the use of cyclic irradiations alternating short exposures to red and far red light.     

Photocontrol of anthocyanin biosynthesis in tomato

Juvenile anthocyanin biosynthesis has been studied in dark-grown seedlings of tomato (Lycopersicon esculentum Mill.) wild types (WTs) and photomorphogenic mutants. During a subsequent 24-hr period of monochromatic irradiation at different fluence rates of red light (R) the fluence-rate response relationships for induction of anthocyanin in all the WTs are similar, yet complex, showing a response at low fluence rates (LFRR) followed by a fluence rate-dependent high irradiance response (HIR). In the hypocotyl this response is restricted to the sub-epidermal layer of cells. The high-pigment-1 (hp-1) mutant exhibits a strong amplification of both response components. Theatroviolacea (atv) mutant shows strongest amplification of the HIR component. In contrast, a transgenic line overexpressing an oat phytochrome A gene (PHYA3 ⁺) shows a most dramatic amplification of the LFRR component. The far-red light (FR)-insensitive (fri) mutant, deficient in phytochrome A (phyA), lacks the LFRR component whilst retaining a normal HIR. The temporarily R-insensitive (tri) mutant, deficient in phytochrome B1 (phyB1) retains the LFRR, but lacks the HIR. Thehp-1,fri andhp-1,tri double mutant, exhibit amplified, yet qualitatively similar responses to the monogenicfri andtri mutants. Thefri,tri double mutant lacks both response components in R, but a residual response to blue light (B) remains. Similarly, theaurea (au) mutant deficient in phytochrome chromophore biosynthesis and presumably all phytochromes, lacks both response components in the R and FR regions of the spectrum. Experiments at other wavelengths demonstrate that while there is only a small response in the FR spectral region (729 nm) in tomato, there is an appreciable HIR response in the near FR at 704 nm, which is retained in thetri mutant. This suggests that the labile phyA pool participates in the HIR at this wavelength. The intense pigmentation (Ip) mutant appears to be specifically deficient in the B1 induced anthocyanin biosynthesis. Adult plants, grown under fluorescent light/dark cycles, show a reduction of anthocyanin content of young developing leaves upon application of supplemtary or end-of-day FR. The involvement of different phytochrome species in anthocyanin biosynthesis based on micro-injection studies into theau mutant and studies using type specific phytochrome mutants is discussed.     

Photocontrol of betaxanthin synthesis in Celosia plumosa seedlings

Light stimulates the betaxanthin accumulation in Celosia plumosa. The induction is partially reversed by far-red and inhibited by actinomycin D, puromycin, salicylaldoxime and 2,4-dinitrophenol, while 3-(3,4-dichlorophenyl)-1,1-dimethylurea has an inhibitory effect only when photosynthesis is operative. In darkness betaxanthins synthesis is promoted by kinetin.     

Photosensitivity of seedlings differing in their potential to synthesize anthocyanin

In the present report the suggestion (Paech, K. 1950. Biochemie und Physiologie der sekundären Pflanzenstoffe. - Springer, Berlin, pp. 201–203) was tested that the photosynthetic apparatus requires light protection during the early phase of its development and that this is the reason (in a teleonomic sense) for the transient formation of large amounts of juvenile anthocyanin in outer tissue layers of seedlings and young leaves of deciduous trees and shrubs. Seedlings of two species ( Sinapis alba L. and Sesamum indicum L.) which differ in their potential to produce anthocyanin were compared under identical light conditions. The results obtained are compatible with the idea that juvenile anthocyanins are involved in photoprotection. However, the experimental results also indicate that full photostability of the plastid is attained - irrespective of the presence or absence of anthocyanin - once a certain amount of chlorophyll has been accumulated. Thus, photosensitivity of a seedling under natural light conditions is restricted to an early phase of development prior to intense greening.     

Photocontrol of phenylalanine ammonia-lyase in barley seedlings treated with pyridazinone inhibitors of chloroplast development

Seedlings imbibed for 48 hr in aqueous solutions of the pre-emergent herbicide Sandoz 6706, or its presumably active conversion product Norflurazon, grow into albino plants in white light. Neither herbicide has any effect on PAL in dark grown barley shoots. In white light, however, pretreatment with 100 μM herbicide causes an increase in barley shoot PAL of about 50% over that found in untreated plants. Barley root PAL is stimulated by 0.1 μM Sandoz 6706 but inhibited by higher concentrations. Mung bean primary leaves show dose responses similar to barley roots. The herbicides have no effect in continuous red light, yet blue light is as effective as white light in eliciting PAL responses. The results are discussed in relation to the subcellular distribution of PAL.     

Anthocyanin formation in turnip seedlings (Brassica rapa L.): Evidence for two light steps in the biosynthetic pathway

Summary In turnip seedlings, anthocyanin synthesis can be induced with light as soon as water uptake enables the seed coat to be removed. In very young seedlings the main site of production is in the cotyledons but this moves to the hypocotyl when the period of dark growth, before transfer to the light, is increased. The total amount of anthocyanin formed decreases as the seedlings become older. It is suggested that a substance stored in the cotyledons is needed for anthocyanin synthesis and that this substance disappears during growth in the dark. It cannot be replaced by known anthocyanin precursors such as phenylalanine, acetate, shikimic acid and sugars.Anthocyanin synthesis in the hypocotyl is almost completely prevented when the cotyledons are excised, or covered: no anthocyanin is formed in the hypocotyl when the cotyledons alone are irradiated. Cotyledons that have been excised from the hypocotyl synthesize about as much anthocyanin as is formed in the whole intact seedling, but covering the hypocotyl does not increase the amount formed in the cotyledons. These results suggest that pigment synthesis begins in the cotyledons, where a light reaction is needed for the formation of a precursor; the precursor is translocated to the hypocotyl where a second photochemical reaction is required for anthocyanin synthesis. If translocation to the hypocotyl is prevented, anthocyanin is formed in the cotyledons. The nature of the transported precursor is not yet known.

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Zusammenfassung In Keimlingen vonBrassica rapa kann Anthocyansynthese durch Licht induziert werden, sobald es möglich ist, die Samenschale zu entfernen. In den jüngsten Keimlingen sind die Kotyledonen der Ort stärkster Anthocyanbildung, in älteren Keimlingen das Hypokotyl. Die Gesamtmenge an gebildetem Anthocyan nimmt mit zunehmendem Alter der Keimlinge ab. Es wird vermutet, daß eine für Anthocyansynthese notwendige Substanz in den Kotyledonen gespeichert ist und während des Wachstums im Dunkeln abnimmt. Diese Substanz konnte durch bekannte Anthocyanvorstufen wie Phenylalanin, Acetat, Shikimisäure und Zucker nicht ersetzt werden.Anthocyansynthese ist im Hypokotyl fast vollständig unterdrückt, wenn die Kotyledonen entfernt oder verdunkelt werden: Kein Anthocyan wird im Hypokotyl gebildet, wenn die Kotyledonen allein belichtet werden. Isolierte Kotyledonen synthetisieren ungefähr die gleiche Menge Anthocyan wie intakte Keimlinge, aber eine Verdunkelung des Hypokotyls bewirkt keine Steigerung der Anthocyanbildung in den Kotyledonen. Diese Ergebnisse lassen vermuten, daß die Synthese von Anthocyan in den Kotyledonen beginnt, wo eine lichtabhängige Reaktion zur Bildung einer Zwischenstufe notwendig ist; diese Zwischenstufe wird in das Hypokotyl transportiert, wo eine zweite photochemische Reaktion für Anthocyansynthese erforderlich ist. Wird der Transport in das Hypokotyl verhindert, findet Anthocyansynthese in den Kotyledonen statt. Über die Natur dieser Zwischenstufe ist jedoch noch nichts bekannt.

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With 9 Figures in the Text     

Red-far red reversibility of anthocyanin synthesis in dark-grown and light-pretreated seedlings

The rate of escape from red—far red reversibility for anthocyanin synthesis is lower in dark-grown than in light-pretreated seedlings of Brassica oleracea L. Red Acre, Secale cereale L. Cougar, and Lycopersicon esculentum Mill. Beefsteak. This observation is consistent with the suggestion that there might be two pools of phytochrome, a labile one, characterized by fast disappearance of phytochrome—far-red absorbing form, and a stable one, characterized by slow disappearance of phytochrome—far-red absorbing form, and that the proportion between the two pools might be different in dark-grown and light-pretreated seedlings.     

Genetic regulation and photocontrol of anthocyanin accumulation in maize seedlings.

The flavonoid pathway leading to anthocyanin biosynthesis in maize is controlled by multiple regulatory genes and induced by various developmental and environmental factors. We have investigated the effect of the regulatory loci R, B, and Pl on anthocyanin accumulation and on the expression of four genes (C2, A1, Bz1, and Bz2) in the biosynthetic pathway during an inductive light treatment. The results show that light-mediated anthocyanin biosynthesis is regulated solely by R; the contributions of B and Pl are negligible in young seedlings. Induction of the A1 and Bz2 genes by high fluence-rate white light requires the expression of a dominant R allele, whereas accumulation of C2 and Bz1 mRNA occurs with either a dominant or recessive allele at R. A1 and Bz2 mRNA accumulate only in response to high fluence-rate white light, but Bz1 is fully expressed in dim red light. Some C2 mRNA is induced by dim red light, but accumulation is far greater in high fluence-rate white light. Furthermore, expression from both dominant and recessive alleles of the regulatory gene R is enhanced by high fluence-rate white light. Seedlings with a recessive allele at R produce functional chalcone synthase protein (the C2 gene product) but accumulate no anthocyanins, suggesting that, in contrast to the R-mediated coordinate regulation of C2 and Bz1 observed in the aleurone, C2 expression in seedlings is independent of R and appears to be regulated by a different light-sensitive pathway.     

Ultraviolet A-specific induction of anthocyanin biosynthesis in the swollen hypocotyls of turnip (Brassica rapa)

Ultraviolet A (UV-A)-mediated regulation of anthocyanin biosynthesis was investigated in swollen hypocotyls of the red turnip 'Tsuda'. The shaded swollen hypocotyls which contained negligible anthocyanin were exposed to artificial light sources including low fluence UV-B, UV-A, blue, red, far-red, red plus UV-A, far-red plus UV-A, and blue plus red. Among these lights, only UV-A induced anthocyanin biosynthesis and co-irradiation of red or far-red with UV-A did not affect the extent of UV-A-induced anthocyanin accumulation. The expression of phenylalanine ammonia lyase (PAL; EC 4.3.1.5), chalcone synthase (CHS; EC 2.3.1.74), flavanone 3-hydroxylase (F3H; EC 1.14.11.9), dihydroflavonol 4-reductase (DFR; EC 1.1.1.219), and anthocyanidin synthase (ANS; EC 1.14.11.19) genes was increased with time during a 24 h exposure to UV-A. In contrast, irradiation with red, blue, UV-B, and a combination of blue with red failed to induce CHS expression. Microarray analysis showed that only a few genes, including CHS and F3H, were induced significantly by UV-A, while a separate set of many genes was induced by low fluence UV-B. The UV-A-specific induction of anthocyanin biosynthesis and the unique gene expression profile upon UV-A irradiation as compared with blue and UV-B demonstrated that the observed induction of anthocyanin biosynthesis in red turnips was mediated by a distinct UV-A-specific photoreceptor, but not by phytochromes, UV-A/blue photoreceptors, or UV-B photoreceptors.     

Effects of growth regulators on light-dependent anthocyanin production in Zea mays seedlings

Rengel, Z. and Kordan, H. A. 1987. Effects of growth regulators on light-dependent anthocyanin production in Zea mays seedlings.
The effects of ethylene, indolyl- and naphthylacetic acids, zeatin, benzyladenine, gib-berellic acid and triiodobenzoic acid on anthocyanin production in seedlings of Zea mays L. cv. Golden Bantam were investigated. Endogenously produced and exogen-ously supplied ethylene, as well as the other growth regulators tested markedly suppressed anthocyanin formation. Except for triiodobenzoic acid, the other growth regulators stimulated ethylene production, the amounts produced in the light being larger than those in the dark. Absorption of ethylene by permanganate as well as inhibition of ethylene production or action by Co²⁺ or Ag⁺ increased anthocyanin formation in maize seedlings above the level found in the control plants. The inhibiting effect of auxins and cytokinins on anthocyanin production was reversed by Co²⁺ or Ag⁺. In contrast, decreased anthocyanin formation caused by gibberellic acid or triiodobenzoic acid seemed unrelated to ethylene and could not be alleviated by Co²⁺ or Ag+.     

Gibberellic acid bioassay based on the inhibition of anthocyanin production in tomato seedlings

A simple bioassay of gibberellic acid (GA₃) based on the GA₃-induced reduction of anthocyanin contents in young seedlings of tomato is described and compared with the amaranthin reduction test. It was found that GA₃-induced reduction of anthocyanin in tomato seedlings was linear from 10⁻⁵ to 10 mg 1⁻¹ GA₃ whereas the reduction of amaranthin inAn aranthus caudatus seedlings was linear from 10⁻³ to 10 mg 1⁻¹ GA₃. From these results, it is concluded that the anthocyanin reduction test for GA₃ is more sensitive at lower concentrations of GA₃ than the amaranthin reduction test.     

Effectiveness of intermittent light treatments on anthocyanin synthesis in dark-grown and light-pretreated seedlings

Differences in the extent of anthocyanin production between intermittent light treatments with short and long dark intervals between successive irradiations are more pronounced in dark-grown than in light-pretreated cabbage seedlings. This observation is consistent with the hypothesis, based on destruction kinetics data, that there might be two pools of phytochrome, a labile one and a stable one, present in different proportions in dark-grown and light-pretreated seedlings, and suggests that light-dependent changes of the stable to labile phytochrome ratio might be physiologically significant in the photoregulation of photomorphogenic responses.     

Change in sensitivity to far-red irradiation on anthocyanin biosynthesis in red cabbage seedlings

Abstract. Anthocyanin biosynthesis in red cabbage seedlings has been shown to be under a red/far-red (R/FR) reversible phytochrome control. The 'escape' of anthocyanin synthesis from FR photoreversibility occurred between 12 and 20 h. However, a similarity exists between the escape curve and the temporal change in sensitivity to FR alone, which suggests that some of the 'escape' may be due to the promotive effect of FR. Some escape times may not therefore be a true measure of the duration of Pfr action, contrary to the traditional view.