Photoregulation of Phenylalanine Ammonia Lyase is not Correlated with Anthocyanin Induction in Photomorphogenetic Mutants of Tomato(Lycopersicon esculentum)

Photoregulation of phenylalanine ammonia lyase (PAL)(EC 4.3.1.5 [EC] )was analyzed in wild type (WT) and mutants: phytochrome dencient-awrea(au), high pigment exhibiting exaggerated phytochrome response(hp) and the double mutant (au.hp) of tomato (Lycopersicon esculentum(Mill.) cv. Ailsa Craig). Red light, acting via phytochrome,stimulates PAL activity in cotyledons and hypocotyls of tomatoseedlings. The time course of photoinduction of PAL in cotyledonsof the mutants (au and au.hp) and WT seedlings has a peak ofactivity at 4 h, after which the activity falls sharply, exceptin hp seedlings where activity is maintained at a high level.In hypocotyls, photoinduction of PAL also shows an initial rise,reaching a maximum at 3 h, followed by a sharp decline in themutants (au and au.hp) and WT seedlings. However in hp seedlingsphotoinduction of PAL is about 3 fold that in WT. The photoinductionof PAL appears to be dependent on de novo synthesis of proteinand nucleic acids. The use of a PAL specific inhibitor a-aminooxyß-phenylpropionic acid indicated that PAL is an essentialcomponent of the anthocyanin biosyn-thetic pathway in the tomatoseedlings. However, a comparison of anthocyanin biosynthesis[Adamse et al. (1989) Photochem. Photobiol. 50: 107] and PALphotoinduction data revealed that phytochrome mediated inductionof PAL and anthocyanin in the tomato seedlings are not correlated.While au and au.hp mutant seedlings show a similar increasein PAL level as in the WT, there is little formation of anthocyaninin these mutant seedlings. The results indicate that, in contrastto the photoregulation of anthocyanin synthesis which is dependenton the presence of the labile phytochrome (IP) pool in tomatoseedlings, the photoinduction of PAL is mediated via a smallpool of phytochrome in au mutant: stable phytochrome (sP) ora residual /P pool. (Received August 6, 1991; Accepted September 27, 1991)     

Phytochrome-induced flavonoid biosynthesis in mustard (Sinapis alba L.) cotyledons. Enzymic control and differential regulation of anthocyanin and quercetin formation

Phytochrome-induced increases in enzyme activities for phenylalanine ammonia-lyase (EC 4.3.1.5) and chalcone isomerase (EC 5.5.1.6), and in amounts of the related end products, anthocyanin and the flavonol, quercetin, were measured in cotyledons of mustard (Sinapis alba L.). There was no correlation between the activities of these enzymes and the rate of anthocyanin accumulation; however, some correlation was found with the quercetin accumulation rate. Since anthocyanin and flavonol accumulation is spatially separated in mustard (flavonols in the upper epidermis, anthocyanin in the lower epidermis), it was possible to measure anthocyanin-associated phenylalanine ammonia-lyase independently. This activity correlated well with the accumulation rate for anthocyanin during the first few hours after induction. The phytochrome effect on anthocyanin formation differed from that on quercetin formation: anthocyanin was strongly induced by continuous far-red light and by both continuous red light and red light pulses, whereas quercetin was only effectively induced by continuous far-red light.Abbreviations CHI chalcone isomerase - PAL phenylalanine ammonia-lyase     

Analysis of the Expression of Anthocyanin Pathway Genes in Developing Vitis vinifera L. cv Shiraz Grape Berries and the Implications for Pathway Regulation

Anthocyanin synthesis in Vitis vinifera L. cv Shiraz grape berries began 10 weeks postflowering and continued throughout berry ripening. Expression of seven genes of the anthocyanin biosynthetic pathway (phenylalanine ammonia lyase [PAL], chalcone synthase [CHS], chalcone isomerase [CHI], flavanone-3-hydroxylase [F3H], dihydroflavonol 4-reductase [DFR], leucoanthocyanidin dioxygen-ase [LDOX], and UDP glucose-flavonoid 3-o-glucosyl transferase [UFGT]) was determined. In flowers and grape berry skins, expression of all of the genes, except UFGT, was detected up to 4 weeks postflowering, followed by a reduction in this expression 6 to 8 weeks postflowering. Expression of CHS, CHI, F3H, DFR, LDOX, and UFGT then increased 10 weeks postflowering, coinciding with the onset of anthocyanin synthesis. In grape berry flesh, no PAL or UFGT expression was detected at any stage of development, but CHS, CHI, F3H, DFR, and LDOX were expressed up to 4 weeks postflowering. These results indicate that the onset of anthocyanin synthesis in ripening grape berry skins coincides with a coordinated increase in expression of a number of genes in the anthocyanin biosynthetic pathway, suggesting the involvement of regulatory genes. UFGT is regulated independently of the other genes, suggesting that in grapes the major control point in this pathway is later than that observed in maize, petunia, and snapdragon.     

In vitro selection of mung bean and tomato for improving tolerance to NaCl

Mung bean and tomato were in vitro selected from cotyledons on MS medium for improved tolerance to NaCl. The growth responses; the Na, K, proline and anthocyanin contents; and activities of phenylalanine ammonia lyase (PAL, EC 4.3.1.5), tyrosine ammonia lyase (TAL, EC 4.3.1) and chalcone isomerase (CI, EC 5.5.1.5) of the selected plants were characterised and compared with those of the original plants in relation to treatment with NaCl. The treatments significantly reduced fresh and dry weights of shoots and roots; the reduction was least pronounced in selected plants. Meanwhile, Na content was significantly increased; however, K was decreased, a trend that was obvious in original plants but withdrawn following in vitro selection with a consequent lowering in Na/K ratio. In addition, proline was greatly induced by NaCl; the induction was most pronounced in selected plants. Moreover, NaCl significantly increased anthocyanin and activities of PAL, TAL and CI in shoots and roots of both species; the increase was lesser in the selected than in the original plants. These findings indicated that selection of mung bean and tomato resulted in a recovery of growth, overproduction of proline and K and withdrawal of Na and secondary metabolism parameters relative to original plants pointing out to an improved tolerance to NaCl following in vitro selection.     

Cloning and molecular analysis of structural genes involved in flavonoid and stilbene biosynthesis in grape (Vitis vinifera L.)

Genes involved in flavonoid and stilbene biosynthesis were isolated from grape (Vitis vinifera L.). Clones coding for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydoxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX) and UDP glucose:flavonoid 3-O-glucosyl transferase (UFGT), were isolated by screening a cDNA library, obtained from mRNA from seedlings grown in light for 48 h using snapdragon (Antirrhinum majus) and maize heterologous probes. A cDNA clone coding for stilbene synthase (StSy) was isolated by probing the library with a specific oligonucleotide. These clones were sequenced and when the putative products were compared to the published amino acid sequence for corresponding enzymes, the percentages of similarity ranged from 65% (UFGT) to 90% (CHS and PAL). The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StSy genes belong to large multigene families, while the others are present in one to four copies per haploid genome. The steady-state level of mRNAs encoded by the flavonoid biosynthetic genes as determined in young seedlings is coordinately induced by light, except for PAL and StSy, which appear to be constitutively expressed.     

Oxidative stress in herbicide-treated broad bean and maize plants

Treatments of broad bean and maize seedlings with fluometuron, atrazine or rimsulfuron affected some parameters of oxidative stress. Fluometuron significantly reduced activity of Hill reaction (PSII), chlorophyll a+b contents and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) in leaves of both species and significantly increased contents of H₂O₂, lipid peroxides and carbonyl groups during the whole experiment. There were, moreover, significant inhibitions in activities of superoxide dismutase (SOD; E.C. 1.15.1.1), catalase (CAT; E.C. 1.11.1.6), ascorbate peroxidase (APX; E.C. 1.11.1.11) and guaiacol peroxidase (GPX; E.C. 1.11.1.7). Response to atrazine was, to some extent, similar to fluometuron throughout the entire experiment in broad bean and up mostly to the 12^th day of the experiment in maize. The herbicide effect was more pronounced in broad bean than maize. These results point to indicate an occurrence of oxidative stress in both species by fluometuron and only in broad bean by atrazine. The increase in H₂O₂ content accompanied with drop in activities of SOD, CAT and peroxidases indicates a decline in its detoxification rather than increase in its synthesis. On the contrary, rimsulfuron seemed to have no effect on most of the tested parameters although there were transient significant increases in H₂O₂, lipid peroxides and carbonyl groups as well as activities of SOD, CAT, APX and GPX. These findings, based on the recovery in oxidative stress, indicate that fluometuron is involved in oxidative stress generation in both species but atrazine only in broad bean while rismulfuron is not in both species.     

Action pattern of polysaccharide lyases on glycosaminoglycans

The action pattern of polysaccharide lyases on glycosaminoglycansubstrates was examined using viscosimetric measurements andgradient polyacrylamide gel electrophoresis (PAGE). Heparinlyase I (heparinase, EC 4.2.2.7 [EC] ) and heparin lyase II (no ECnumber) both acted on heparin in a random endolytic fashion.Heparin lyase II showed an ideal endolytic action pattern onheparan sulphate, while heparin lyase I decreased the molecularweight of heparan sulphate more slowly. Heparin lyase III (heparitinase,EC 4.2.2.8 [EC] ) acted endolytically only on heparan sulphate anddid not cleave heparin. Chondroitin ABC lyase (chondroitinaseABC, EC 4.2.2.4 [EC] ) from Proteus vulgaris acted endolytically onchondroitin-6-sulphate (chondroitin sulphate C) and dermatansulphate at nearly identical initial rates, but acted on chondroitin-4-sulphate(chondroitin sulphate A) at a reduced rate, decreasing its molecularweight much more slowly. Two chondroitin AC lyases (chondroitinaseAC, both EC 4.2.2.5 [EC] ) were examined towards chondroitin-4- and-6-sulphates. The exolytic action of chondroitin AC lyase Afrom Arthrobacter aurescens on both chondroitin-4- and -6-sulphateswas demonstrated viscosimetrically and confirmed using bothgradient PAGE and gel permeation chromatography. ChondroitinAC lyase F from Flavobacterium heparinum (Cytophagia heparinia)acted endolytically on the same substrates. Chondroitin B lyase(chondroitinase B, no EC number) from F.heparinum acted endolyticallyon dermatan sulphate giving a nearly identical action patternas observed for chondroitin ABC lyase acting on dermatan sulphate. action pattern chondroitin lyase glycosaminoglycan heparin lyase.     

Development of Enzymes of the Glyoxylate Cycle during Senescence of Pumpkin Cotyledons

The presence and activities of isocitrate lyase (EC 4.1.3.1 [EC] )and malate synthase (EC 4.1.3.2 [EC] ) were studied during senescenceof pumpkin cotyledons (Cucurbita sp. Amakuri Nankin). Afterincubation of detached cotyledons in permanent darkness, theactivities appeared and increased up to the eighth day and thendeclined, while the activities of catalase (EC 1.11.1.6 [EC] ), glycolateox-idase (EC 1.1.3.1 [EC] ), and hydroxypyruvate reductase (EC 1.1.1.81 [EC] )decreased dramatically. After fractionation of cell organellesby sucrose density gradient, we detected isocitrate lyase andmalate synthase activities in peroxisomal fractions. The activityof the two key enzymes of the glyoxylate cycle also increasedduring senescence in vivo and we confirmed the presence of thetwo enzymes in the peroxisomal fractions after sucrose gradientcentrifugation. At every point examined, the level of malatesynthase was demonstrated by immunoblotting. It is concludedthat the development of isocitrate lyase and malate synthaseactivities represents the transition from leaf peroxisomes toglyoxysomes and that such a phenomenon is associated with senescence. (Received January 25, 1991; Accepted March 22, 1991)     

Physiological Basis for a Cycloheximide-induced Soft Rot of Potatoes by Pseudomonas fluorescens

Cycloheximide renders discs of potato tissue (Solanum tuberosum,cultivar Kennebec) susceptible to soft rot by a non-pathogenicisolate of Pseudomonas fluorescens. Pectate lyases (E.C. 4.2.99.3 [EC] )are the dominant extracellular macerating agents produced bythe test organism. Potato discs aged 24 h become resistant tomaceration by purified lyase preparations. Cycloheximide blocksthe development of resistance by inhibiting suberization. Thesite of inhibition is thought to be the cycloheximide-sensitivesynthesis of phenylalanine ammonia-lyase (E.C. 4.3.1.5 [EC] ) in potatodiscs. This enzyme is necessary for production of phenolic precursorsof suberin. Comparison of tissue from a number of potato cultivarscorrelates the synthesis of phenylalanine ammonia-lyase withresistance of discs to attack by the Pseudomonad. Resistance of potato tissue to pectate lyase is also affectedby intrinsic reactions not involving suberization. Resistanceincreases in fresh unsuberized discs when tubers are transferredfrom cold storage to room temperature before use. Resistancedecreases rapidly when tubers are transferred back to the cold.The intrinsic resistance appears to increase in the surfacelayer of cells in ageing discs. It is estimated that intrinsicreactions and suberization contribute equally to resistanceof aged discs to pectate lyase maceration.     

Anthocyanin accumulation and changes in activities of phenylalanine ammonia-lyase and chalcone synthase in roselle (Hibiscus sabdariffa L.) callus cultures

Time-course changes in anthocyanin accumulation, phenylalanine ammonia-lyase activity and chalcone synthase activity were examined in roselle callus tissues incubated under different culture conditions. Phenylalanine ammonia-lyase activity was not affected by either the kind of auxin supplemented to the medium or light regime. In contrast, chalcone synthase activity was markedly suppressed when the callus was cultured with a medium containing indole-3-acetic acid instead of 2,4-dichlorophenoxyacetic acid (2,4-D) or in the dark. The results imply that in roselle callus cultures chalcone synthase plays a more important role in anthocyanin biosynthesis regulated by 2,4-D and light irradiation than phenylalanine ammonialyase.Abbreviations LS Linsmaier and Skoog - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - PAL phenylalanine ammonia-lyase - CHS chalcone synthase     

Changes in activities of enzymes involved in flavonoid metabolism during the initiation and suppression of anthocyanin synthesis in carrot suspension cultures regulated by 2,4-dichlorophenoxyacetic acid

When anthocyanin synthesis was induced in cell suspension cultures of carrot ( Daucus carota L. cv. Kurodagosun) by transfer to medium lacking 2,4-dichlorophenoxyacetic acid (2,4-D), phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), chalcone synthase (CHS, EC 6.-.-.-), and chalcone-flavanone isomerase (CHFI, EC 5.5.1.6) activities appeared, reaching maxima 6–7 days after transfer. The maximum specific activity of CHS was much lower than that of PAL or CHFI. In a medium containing 2,4-D, no anthocyanin was synthesized, PAL and CHFI activities were suppressed and CHS activity could not be detected at all. The activities of PAL and CHS in cells cultured without 2,4-D for 6 days began to decrease within 3–6 h of 2,4-D addition. CHS activity was completely repressed 24–36 h after the addition, but CHFI activity was almost unchanged at this time. After culture without 2,4-D for 6 days, cell suspensions were transferred to fresh media either lacking or containing 2,4-D. After transfer, PAL increased in both media within 3 h, whereas CHS activity and anthocyanin accumulation were coordinated and both were completely regulated by 2,4-D. Changes in CHS activity rather than PAL activity correlate with changes in anthocyanin accumulation under various culture conditions.     

Glyoxylate Cycle Enzymes in Peroxisomes Isolated from Petals of Pumpkin (Cucurbita sp.) during Senescence

The activities of the two unique enzymes of the glyoxylate cycle,isocitrate lyase (EC 4.1.3.1 [EC] ) and malate synthase (EC 4.1.3.2 [EC] ),were undetectable in petals of pumpkin (Cucurbita sp. AmakuriNankin) until the end of blooming, but they appeared duringsenescence. The activity of catalase (EC 1.11.1.6 [EC] ) increased,glycolate oxidase (EC 1.1.3.1 [EC] ) activity did not change, whilehydroxypyruvate reductase (EC 1.1.1.81 [EC] ) activity peaked at fullblooming stage and declined thereafter. After fractionationof cellular organelles on a sucrose density gradient, we detectedisocitrate lyase and malate synthase activities in peroxisomalfractions only from petals at the senescing stage. Northernblot analysis revealed that malate synthase mRNA increased duringpetal senescence. Citrate synthase (EC 4.1.3.7 [EC] ) and malate dehydrogenase(EC 1.1.1.37 [EC] ) activities were also present, while aconitase(EC 4.2.1.3 [EC] ) was not detectable in peroxisomal fractions. Moreoverthe presence of 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35 [EC] )and urate oxidase (EC 1.7.3.3 [EC] ) in the peroxisomal fractionsfrom senescing petals indicates that peroxisomes could be involvedboth in the ß-oxidation pathway and in the purinecatabolism during petal senescence. (Received May 25, 1991; Accepted September 25, 1991)     

The effect of n-propyl gallate on the formation of ethylene during protoplast isolation in sugarbeet (Beta vulgaris L.)

The formation of ethylene during isolation of mesophyll protoplastsfrom leaves of in vitro cultured sugarbeet (Beta vulgaris L.)seedlings was monitored. The addition of the lipoxygenase (EC1.13.11.12 [EC] ) inhibitor n-propyl gallate to the isolation mediumsignificantly reduced the amount and rate of ethylene production.The relevance of cell physiology on protoplast regenerationis discussed. Key words: Beta vulgaris L., protoplasts, ethylene, lipoxygenase inhibitor, regeneration     

Regulation of Flavonoid Biosynthetic Genes in Germinating Arabidopsis Seedlings

Many higher plants, including Arabidopsis, transiently display purple anthocyanin pigments just after seed germination. We observed that steady state levels of mRNAs encoded by four flavonoid biosynthetic genes, PAL1 (encoding phenylalanine ammonia-lyase 1), CHS (encoding chalcone synthase), CHI (encoding chalcone isomerase), and DFR (encoding dihydroflavonol reductase), were temporally regulated, peaking in 3-day-old seedlings grown in continuous white light. Except for the case of PAL1 mRNA, mRNA levels for these flavonoid genes were very low in seedlings grown in darkness. Light induction studies using seedlings grown in darkness showed that PAL1 mRNA began to accumulate before CHS and CHI mRNAs, which, in turn, began to accumulate before DFR mRNA. This order of induction is the same as the order of the biosynthetic steps in flavonoid biosynthesis. Our results suggest that the flavonoid biosynthetic pathway is coordinately regulated by a developmental timing mechanism during germination. Blue light and UVB light induction experiments using red light- and dark-grown seedlings showed that the flavonoid biosynthetic genes are induced most effectively by UVB light and that blue light induction is mediated by a specific blue light receptor.     

Collapse of Peroxide-Scavenging Systems in Apple Flower-Buds Associated with Freezing Injury

Changes in the metabolic activities of peroxide-producing systemsand peroxide-scavenging systems after freezing and thawing inflower buds of the apple, Malus pumila Mill., were studied withspecial reference to freezing injury. In flower buds of the‘McIntosh’ apple that were frozen below lethal temperatures,the activity of NADH-Cyt c reductase (EC 1.6.99.3 [EC] ), one of theenzymes in the electron-transport chains that are related tothe peroxide-producing systems, decreased slightly, while thatof Cyt c oxidase (EC 1.9.3.1 [EC] ) hardly changed. By contrast, theactivities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49 [EC] ),dehydroascorbate reductase (EC 1.8.5.1 [EC] ) and ascorbate peroxidase(EC 1.11.1.11 [EC] ), which are involved in the peroxide-scavengingsystems, decreased to very low levels. The activity of glyceraldehyde-3-phosphatedehydrogenase (EC 1.2.1.12 [EC] ) also decreased markedly. However,little change was observed in the activities of hexokinase (EC2.7.1.1 [EC] ), glucosephosphate isomerase (EC 5.3.1.9 [EC] ), glutathionereductase (EC 1.6.4.2 [EC] ) and glutathione peroxidase (EC 1.11.1.9 [EC] ).Examination of substrates involved in the peroxide-scavengingsystems revealed that the levels of glucose-6-phosphate andfructoses-phosphate decreased to approximately 10^–4 to10^–5 M and 10^–5 M, respectively, and the levelsof GSH decreased to about 10^–5 M or became barely detectable.A decrease in the levels of GSSG also occurred while levelsof ascorbate rose slightly. Similar results were observed withflower buds from ‘Starking Delicious’ and ‘Jonathan’apple trees. These results suggest that the freezing injury to apple flower-budsis closely related to the collapse of the peroxide-scavengingsystems that are coupled with the pentose phosphate cycle. Theresults also suggest that the dysfunction of these peroxide-scavengingsystems is caused by H₂O₂, which may be produced during freezingand thawing. (Received March 14, 1992; Accepted June 5, 1992)     

Effect of shade treatment on biosynthesis of catechins in tea plants

When tea plants were shaded with black lawn cloth for severaldays in the field, the accumulations of (—)-epicatechin,(—)-epicatechin-3-gallate, (—)-epigallocatechinand (—)-epigallocatechin-3-gallate decreased in newlydeveloping tea shoots. Radioactive tracer studies showed thatthe conversions of glucose-U-¹⁴C, shikimic acid-G-¹⁴C and phenylalanine-U-¹⁴Cinto (—)-epicatechin and (—)-epigallocatechin moietieswere depressed by the shade treatment for tea plants but theincorporation of trans-cinnamic acid-3-¹⁴C was not affected.The treatment was found to have no significant effect on theactivities of phospho-2-keto-3-deoxy-heptonate. aldolase (EC.4.1.2.15 [EC] ), 3-dehydroquinate synthase (EC. 4.6.1.3 [EC] ), 3-dehydroquinatedehydratase (EC. 4.2.1.10 [EC] ), shikimate dehydrogenase (EC. 1.1.1.25 [EC] )and trans-cinnamate 4-monooxygenase (EC. 1.14.13.11 [EC] ) in theshoots, whereas the activity of phenylalanine ammonia-lyase(EC. 4.3.1.5 [EC] ) clearly decreased. (Received March 17, 1980; )     

Distribution of Secondary Plant Metabolites and Their Biosynthetic Enzymes in Pea (Pisum sativum L.) Leaves : Anthocyanins and Flavonol Glycosides

Leaves of a novel strain of peas (Pisum sativum L.) were used to determine the distribution of secondary metabolites and their biosynthetic enzymes. Leaf epidermal layers in this strain are easily separated from the parenchyma. Anthocyanins and flavonol glycosides were localized in epidermal vacuoles only. Among the biosynthetic enzymes studied, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), S-adenosyl-1-methionine (SAM):caffeic acid and SAM:quercetin methyltransferases (o-dihydric phenol methyltransferase, EC 2.1.1.42) and a flavonoid 7-O-glucosyltransferase (EC 2.4.1.91) were chiefly localized in the parenchyma, whereas trans-cinnamate 4-monooxygenase (EC 1.14.13.11), hydroxycinnamate:CoA ligases (EC 6.2.1.12) and a flavonoid 3-O-glucosyltransferase (EC 2.4.1.91) were found mainly in the epidermis. Flavanone (chalcone) synthase activity was found only in the epidermis, whereas chalcone isomerase (EC 5.5.1.6) was evenly distributed in epidermal and parenchyma tissues.     

Sunlight-induced anthocyanin pigmentation in maize vegetative tissues

Although, in maize, sunlight-regulated anthocyanin formation in vegetative tissues is observed only in the cultivars harbouring homozygous recessive pl loci, the identity of the photoreceptor mediating this process is not yet fully established. In this study the nature of photoreceptor(s) mediating this response was examined using an Indian hybrid maize cultivar (Kanchan-521). The etiolated maize seedlings of this cultivar on exposure to sunlight formed anthocyanin in all vegetative organs. Sunlight elicited photoinduction of anthocyanin with a slow increase between 4-16 h after the sunlight exposure, followed by a rapid increase between 16-24 h. The photoinduction of anthocyanin was primarily mediated by the UV-B component of sunlight and could be elicited by exposure to an artificial UV-B light source. The sunlight-mediated induction of anthocyanin was reduced if the sunlight exposure was terminated with a far-red pulse before transfer to darkness, indicating a coaction of phytochrome in this photoresponse. Exposure to sunlight also stimulated phenylalanine ammonia lyase (PAL) activity in all organs with two temporally separated peaks. The first peak of PAL between 4-12 h was induced by phytochrome, and the second peak of PAL between 12-24 h was induced by UV-B light. These results indicate that the photoinduction of anthocyanin in maize is mediated by a coaction of UV-B light and phytochrome.