Carbohydrate accumulation may be the proximate trigger of anthocyanin biosynthesis under autumn conditions in Begonia semperflorens

Many plant leaves appear red in the autumn, and many papers have focused on the environmental factors and role of anthocyanin in this process. However few papers have examined the substances that are induced during this process. We hypothesised that excess sugar accumulation directly induces anthocyanin accumulation under autumn conditions. Using two methods (restricting phloem movement and exogenous sucrose feeding), we found that both surplus photosynthate and exogenous sucrose could induce anthocyanin biosynthesis, corresponding to up‐regulation of several enzymes involved in anthocyanin biosynthesis (phenylalanine ammonia lyase, chalcone isomerase, dihydroflavonol 4‐reductase and flavonoid 3‐O‐glucosyl transferase) and in transport (glutathione S‐transferase). Our results suggest that excess carbohydrate may be the proximate trigger for induction of anthocyanin biosynthesis in autumn, but only when carbohydrates are accumulated for storage.     

冬季南亚热带森林演替中后期优势树种幼叶光保护策略

为了解演替中期和后期优势树种对冬季不同光强的适应性,对在全光照(100%自然光强)和低光照(30%自然光强)下生长的演替中期优势种木荷(Schima superba)、锥栗(Castanopsis chinensis)和黧蒴(Castanopsis fissa)及演替后期优势种华润楠(Machilus chinensis)、黄果厚壳桂(Cryptocarya coninna)和厚壳桂(Cryptocarya chinensis)的生理生化响应进行了研究。结果表明,与全光照相比,低光照下演替中期优势树种幼叶的非光化学猝灭(NPQ)、类胡萝卜素与叶绿素的比值(Car/Chl)和花色素苷含量下降,细胞质膜渗透率增加;而演替后期优势树种幼叶的花色素苷含量增加、细胞质膜渗透率降低,且受光抑制的程度低(Fv/Fm高)。此外,除总抗氧化能力外,演替中期优势树种幼叶的花色素苷含量、NPQ和Car/Chl均显著低于演替后期优势种。因此,演替后期优势树种可以通过灵活多样的光保护策略来提高对冬季强光环境的适应能力,而演替中期优势种在光保护策略的多样性及光保护能力上均弱于演替后期优势种。     

Transparent Testa Glabra 1 (TTG1) and TTG1-like genes in Matthiola incana R. Br. and related Brassicaceae and mutation in the WD-40 motif

TTG1 (Transparent Testa Glabra 1), a WD-40 repeat protein, is involved in regulation of flavonoid/anthocyanin biosynthesis, seed coat (mucilage) development/pigmentation and trichome formation in leaves. Here, we characterized the TTG1 gene of Matthiola incana wild type ( e locus), showing 85.3% similarity to TTG1 of A. thaliana on the nucleotide level and 96.2% on the protein level. A white-flowered and glabrous mutant, line 17, of M. incana exhibits one nucleotide change, leading to an amino acid substitution directly in the WD motif (W158R). Correspondingly, the DFR (dihydroflavonol 4-reductase) gene, in which the expression is known to be dependent on TTG1, is not expressed in Matthiola mutant lines 17 (and 19). Comparison of the GC content of the Matthiola TTG1 (54.1%) and Arabidopsis TTG1 (46.1%) genes revealed a strong difference, mostly obtained by neutral substitutions (C to T transitions). To examine whether this is an ecologically influenced trend, a fragment of TTG1 was characterized from another Matthiola species ( M. tricuspidata ) and from Malcolmia flexuosa subsp. naxensis from the eastern Mediterranean, near a beach with sandy and salty soils. Both Matthiola species have a higher GC content in the TTG1 gene than Arabidopsis and the closer-related Malcolmia , indicating that the GC content is rather an evolutionary than an ecological signal. A similar WD-40 repeat protein gene (containing no intron in the 3' untranslated region) with high similarity to the Arabidopsis TTG1 -like ( AtAN11 ) gene was found in Matthiola .     

Phenetics in Tree Peony Species from China by Flower Pigment Cluster Analysis

Paeonia   section Moutan DC. (fifteen accessions) from China. As the pigment markers, five anthocyanins together with three flavone and three flavonol aglycones were used. Principal component analysis (PCA) provided five eigenvectors from nineteen pigment patterns, in which peonidin and cyanidin as well as the types of glycosides greatly influenced the first factor, Z ₁. The Euclidean distances of standardized values obtained by eigenvector matrices with five factors (Z ₁ to Z ₅) produced a dendrogram in Ward's minimum variance cluster analysis, which showed good agreement with a classification based on the morphological characteristics of two subsections Vaginatae F.C. Stern and Delavayanae F.C. Stern. The results obtained by PCA and clustering qualify a chemical classification of section Moutan using secondary metabolites, specifically flower pigments, as taxonomic markers. Received 15 January 2001/ Accepted in revised form 6 April 2001     

High anthocyanin accumulation in the dark by strawberry (Fragaria ananassa) callus

Fragaria ananassa (strawberry) callus, which produced high amounts of anthocyanin in the dark, was isolated from a cell line not producing anthocyanin. The isolated callus (FAR) was homogeneous and more than 90% of the cells were pigmented. The FAR callus accumulated more than 1000 g of anthocyanin per g fresh cell in the dark. Four different basal solid media were examined to maintain FAR callus: Though growth rate and anthocyanin concentration were different on each media, total anthocyanin production was about the same at 400 g anthocyanin/0.1 g fresh cell wt after 22 days. This FAR cell line could therefore be used for the industrial production of anthocyanin.     

Germinal reversion of an unstable mutation for anthocyanin pigmentation in soybean

Summary Plants of the w4-mutable line of soybean [Glycine max (L.) Merr.] are chimeral for anthocyanin pigmentation. Mutable plants produce both near-white and purple flowers, as well as flowers of mutable phenotype with purple sectors on near-white petals. It is established here that the mutable trait is conditioned by an unstable recessive allele of the w4 locus that conditions anthocyanin biosynthesis. The gene symbol w4-m is assigned to the mutable allele. Allele w4-m was derived from a stable, wild-type W4 progenitor allele and reverts at high frequency to a stable, wild-type W4 allele. Reversion occurs both early and late during the development of the germ line. Several experiments give estimates of germinal reversion frequency, indicating that approximately 6% of mutable alleles revert to wild-type from one generation to the next. Allele w4-m exhibits many features typical of an allele controlled by a transposable element.     

Gold color in onions (<Emphasis Type="Italic"> Allium cepa</Emphasis>): a natural mutation of the chalcone isomerase gene resulting in a premature stop codon

Unusual gold-colored onions were selected from a F₃ family originating from a cross between US-type yellow and Brazilian yellow onions. HPLC analysis showed that the gold onions contained a significantly reduced amount of quercetin, the most abundant flavonoid in onions. This result indicated that an early step in the flavonoid biosynthesis pathway might be abnormal in these onions. The expression of flavonoid synthesis genes isolated from onions was examined in gold onions and compared to that in onions of other colors by RT-PCR. The results showed that all genes were transcribed in gold onions as in red onions. In order to identify any critical mutations in flavonoid synthesis genes encoding enzymes involved in early steps of the pathway, the genomic sequence of chalcone isomerase (CHI) was obtained. A premature stop codon and a subsequent single base-pair addition causing a frameshift were identified in the coding region of the CHI gene in the gold onions. Co-segregation of the mutant allele of the CHI gene and the gold phenotype was investigated in the original F₂ segregating population. Genotyping of three color groups (red, yellow and gold) of F₂ onions revealed perfect co-segregation of the mutant CHI allele with the gold phenotype. All tested gold F₂ onions were homozygous for the mutant CHI allele. This perfect co-segregation implies that the presence of a premature stop codon in the gold CHI gene results in an inactive CHI. Inactivation of CHI results in a block in the flavonoid biosynthesis pathway and the accumulation of chalcone derivatives, including a yellow pigment which might be responsible for the gold color in onions.Communicated by R. Hagemann     

Effects of initial sucrose concentration on excretion of anthocyanin pigments in suspended cultures of Perilla frutescens cells

Cell cultures of Perilla frutescens, growing on Linsmaier and Skoog medium, released more anthocyanin with 40 to 50 g sucrose/l compared with the control of 30 g sucrose/l of medium. More proteins were also released into the medium with the higher sucrose concentration and the cell volume was smaller, suggesting that the higher osmotic pressure, caused by the high sucrose concentration, may cause these releases. The capacitance of the cultured cells indicated a difference in membrane structure between the cells cultivated with different sucrose concentrations, supporting the hypothesis that cell permeabilization is increased at higher sucrose concentrations.J.-J. Zhong is with the Research Institute of Biochemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China, G.-R. Xu is with the Department of Fermentation Technology, Wuxi Institue of Light Industry, Jiangsu 214036, China. T. Yoshida is with the International Center of Cooperative Research in Biotechnology, Faculty of Engineering. Osaka University, Osaka 565, Japan.