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Chen-Yi Hung, John R. Murray, Sarah M. Ohmann, and Cindy B.S. Tong

The color of red potato tubers is due to an accumulation of anthocyanins in periderm and peripheral cortex tissues. The objective of this study was to characterize changes in anthocyanin content and tuber surface color during tuber development. Using the red tuber-producing potato (Solanum tuberosum L.) cultivar Norland, we observed that chroma (intensity of redness) and anthocyanin content per unit of surface area of greenhouse-grown tubers decreased as tuber weight increased. There was no increase in hue (tint) during the same developmental periods. Using high-performance liquid chromatography (HPLC), we determined that pelargonidin and peonidin are the major anthocyanidins (aglycones of anthocyanins) in the tuber periderm. Northern blot analyses indicated that steady-state mRNA levels of dihydroflavonol reductase (DFR), an anthocyanin biosynthetic enzyme, continued throughout tuber development. These results suggest that anthocyanins are synthesized throughout tuber development, and that cell division and/or enlargement contribute to a decline in chroma and anthocyanin concentration.

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Gordon J. Lightbourn, John R. Stommel, and Robert J. Griesbach

. RNA analysis. Flavonoid gene expression [MYC, MYB, and WD transcription factors, anthocyanin synthase ( Ans ), dihydroflavonol reductase ( Dfr ), and chalcone synthase ( Chs )] was compared under inductive and noninductive environments for

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Ben-Hong Wu, Ning Niu, Ji-Hu Li, and Shao-Hua Li

flavonoids ( Holton and Cornish, 1995 ). Two identified proteins, chalcone synthase [CHS (spot 37)] and dihydroflavonol reductase [DFR (spot 41)], were classified as connected to secondary metabolism (MIPS function 01.20) and were highly expressed in berry

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R.J. Griesbach

The flavonoids from flowers of transgenic Petunia ×hybrida Vilm. plants containing the Al gene from Zea mays L. were characterized. The A1 gene encodes the enzyme dihydroflavonol reductase and was introduced into a mutant petunia defective for this gene. Control, nontransgenic plants produced flowers that contained ≈ 50 ng anthocyanin/100 mg tissue dry weight. Anthocyanin distribution was 63% cyanidin, 28% delphinidin, and 9% pelargonidin. In contrast, the transgenic plants produced flowers that contained ≈ 500 ng anthocyanin/100 mg tissue dry weight, with 34% as cyanidin, 12% as delphlnidin, and 54% as pelargonidin. The increase in anthocyanin production in the transgenic plants resulted in a corresponding molar decrease in flavonol accumulation.

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Neal Courtney-Gutterson

The biosynthetic pathway for anthocyanins has been studied using genetic, biochemical and molecular biological tools. In the past decade, the core pathway genes have been cloned; a number of genes which act to modify anthocyanin structure have been cloned more recently. The first results in color modification have been reduced flower color intensity using gene suppression methods. In particular, we have utilized chalcone synthase (CHS) and dihydroflavonol reductase (DFR) genes and sense suppression in our experimental system, Petunia hybrida, and in the commercial crops, chrysan-themum (Dendranthema morifolium) and rose (Rosa hybrida). In petunia a range of new phenotypes was obtained; genetic stability of suppressed pheno-types will be described. In chrysanthemum a white-flowering derivative of a pink-flowering variety will be described. In rose uniform, partial reduction in pigment intensity throughout the flower was observed in over a dozen trans-genie derivatives of a red-flowering variety.

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Daniel Keifenheim and Cindy Tong*

Anthocyanins are a class of flavonoids that are responsible for pigments in flowers, fruit, and potato periderm. Developing `Norland' potatoes synthesize anthocyanins in periderm tissue when the tubers are mere swollen stolon tips. As the tubers enlarge, anthocyanin accumulation seems to stop, and anthocyanins synthesized early in development seem to be diluted as the tubers enlarge. Expression of dihydroflavonol reductase (DFR) limits anthocyanin synthesis in grape and maize fruit, and in petunia and snapdragon flowers. However, DFR expression in periderm tissue occurred throughout tuber development (Hung et al., 1999). To determine if expression of late anthocyanin pathway genes limit anthocyanin synthesis in developing potato tubers, we performed RNA gel blot analyses. Expression of leucoanthocyanidin dioxygenase and UDP glucose: flavonoid 3-O-glucosyl transferase was observed in swollen stolon tips but not in periderm of later tuber development stages. Surprisingly, expression was also observed in cortex tissue, although that tissue remained white throughout tuber growth.

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Ayako Ikegami, Keizo Yonemori, Akira Kitajima, Akihiko Sato, and Masahiko Yamada

Expression patterns of the genes involved in condensed tannin (CT) biosynthesis during fruit development was investigated in a Chinese pollination-constant, nonastringent (PCNA) persimmon (Diospyros kaki Thunb.) `Luo Tian Tian Shi'. The transcript levels of phenylalanine ammonia-lyase (PAL) and dihydroflavonol reductase (DFR) in `Luo Tian Tian Shi' were detected at high levels throughout the fruit growth. Chalcone synthase (CHS) and flavonol 3-hydroxylase (F3H) also continued to be transcribed during fruit growth, although their levels decreased earlier than PAL and DFR. In contrast, expression levels of these genes declined into undetectable levels at an early stage of fruit development in Japanese PCNA persimmon. In addition, anthocyanidin reductase (ANR), which encodes a key enzyme of the proanthocyanidin biosynthesis, was transcribed at high levels in `Luo Tian Tian Shi' during fruit growth, but not in Japanese PCNA persimmon. By contrast, the expression of D. kaki serine carboxypeptidase-like protein 1 (DkSCPL1) that was obtained from suppression subtractive hybridization (SSH) analysis between artificially astringency-removed fruit and astringent fruit in a different experiment, declined earlier than the other flavonoid biosynthesis genes in `Luo Tian Tian Shi', coincident with the termination of the tannin cell development. In the F1 progeny of the cross between `Luo Tian Tian Shi' and Japanese PCNA `Taishu', similar expression patterns were obtained among segregated PCNA and astringent offspring. These results indicate that Chinese PCNA is different from Japanese PCNA in expression of the genes involved in CT biosynthesis. In conclusion, we clarified that expression of the genes (PAL to ANR, but not SCPL) involved in flavonoid biosynthesis was continuous in the Chinese PCNA cultivar, despite the termination of tannin cell development.

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Dineshkumar Selvaraj, Sherif Sherif, Mohd Sabri Pak Dek, Gopinadhan Paliyath, Islam El-Sharkawy, and Jayasankar Subramanian

ammonia-lyase (PAL), ( B ) chalcone synthase (CHS), ( C ) dihydroflavonol reductase (DFR), ( D ) anthocyanin synthase (ANS), ( E ) UDP-glucose flavanoid 3-O glucosyl transferase ( UFGT 1 ), and ( F ) UDP-glucose flavanoid 3-O glucosyl transferase ( UFGT 2

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Manjul Dutt, Daniel Stanton, and Jude W. Grosser

biosynthetic pathway via the phenylpropanoid pathway and a number of genes are involved ( Jaakola, 2013 ). It could be that one or more of these genes are developmentally regulated in maturing citrus. In Hedera helix L., dihydroflavonol reductase activity

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Huiling Wang, Wei Wang, Weidong Huang, and Haiying Xu

= chalcone synthase; CHI = chalcone isomerase; F3H = flavanone-3-hydroxylase; FLS = flavonol synthase; DFR = dihydroflavonol reductase; ANS = anthocyanidin synthase; ANR = anthocyanidin reductase; UFGT = UDP-Glc:flavonoid 3-O-glucosyltransferase. Salicylic