The COI1 and DFR Genes are Essential for Regulation of Jasmonate-Induced Anthocyanin Accumulation in Arabidopsis

Jasmonates(JAs)are a class of plant hormones that play important roles in the regulation of plant development and plantdefense.It has been shown that Arabidopsis plants produce much higher levels of anthocyanins when treated exogenouslywith methyl jasmonate(MeJA).However,a molecular link between the JA response and anthocyanin production hasnot been determined.The CORONATINE INSENTITIVE1(COI1)gene is a key player in the regulation of many JA-relatedresponses.In the present study,we demonstrate that the COI1 gene is also required for the JA-induced accumulation ofanthocyanins in Arabidopsis.Furthermore,the MeJA-inducible expression of DIHYDROFLAVONOL REDUCTASE(DFR),anessential component in the anthocyanin biosynthesis pathway,was completely eliminated in the coil mutant.Jasmonate-induced anthocyanin accumulation was found to be independent of auxin signaling.The present results indicate that theexpression of both COI1 and DFR genes is required for the regulation of JA-induced anthocyanin accumulation and thatDFR may be a key downstream regulator for this process.     

Regulation of gene expression involved in flavonol and anthocyanin biosynthesis during petal development in lisianthus (Eustoma grandiflorum)

To elucidate gene regulation of flower colour formation, the gene expressions of the enzymes involved in flavonoid biosynthesis were investigated in correlation with their product during floral development in lisianthus. Full-length cDNA clones of major responsible genes in the central flavonoid biosynthetic pathway, including chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3',5'-hydroxylase (F3'5'H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and flavonol synthase (FLS), were isolated and characterized. In lisianthus, the stage of the accumulation of flavonols and anthocyanins was shown to be divided clearly. The flavonol content increased prior to anthocyanin accumulation during floral development and declined when anthocyanin began to accumulate. CHS, CHI, and F3H were necessary for both flavonol and anthocyanin biosynthesis and were coordinately expressed throughout all stages of floral development; their expressions were activated independently at the stages corresponding to flavonol accumulation and anthocyanin accumulation, respectively. Consistent with flavonol and anthocyanin accumulation patterns, FLS, a key enzyme in flavonol biosynthesis, was expressed prior to the expression of the genes involved in anthocyanin biosynthesis. The genes encoding F3'5'H, DFR, and ANS were expressed at later stages, just before pigmentation. The genes responsible for the flavonoid pathways branching to anthocyanins and flavonols were strictly regulated and were coordinated temporally to correspond to the biosynthetic order of their respective enzymes in the pathways, as well as in specific organs. In lisianthus, FLS and DFR, at the position of branching to flavonols and anthocyanins, were supposed to play a critical role in regulation of each biosynthesis.     

二氢黄酮醇 4 还原酶在花青素合成中的功能及调控研究进展

植物色素主要有花青素、类胡萝卜素和生物碱类色素三大类,其中花青素是决定大部分被子植物组织或器官颜色的重要色素。花青素通过类黄酮途径合成,该途径是生物学上研究较多且较为清楚的代谢途径之一。近年来的研究表明,在该途径中除了查尔酮合成酶(chalcone synthase,CHS)、查尔酮异构酶(chalcone isomerase,CHI)和黄烷酮-3-羟化酶(flavanone-3-hydrolase,F3H)起着关键作用外,二氢黄酮醇-4-还原酶(dihydroflavonol 4-reductase,DFR)对花青素的合成也至关重要。DFR可催化3种二氢黄酮醇和2种黄烷酮生成5种不同的花青素前体,且DFR基因家族不同成员对各个底物的催化效率不同,因此它在一定程度上决定着植物中花青素的种类和含量,从而影响植物组织或器官的颜色。该文对近年来国内外有关DFR在花青素合成过程中的生物学功能与调控,包括DFR的特征、作用机制和系统进化以及环境、转录因子和一些结构基因与DFR的关系等方面的研究进展进行了综述,以期为DFR今后的研究和利用基因工程改变植物组织或器官的颜色提供理论依据。     

高等植物二氢黄酮醇4-还原酶基因研究进展

花青素苷是影响植物花瓣呈色的重要色素,而花色是决定花卉观赏价值和商业价值的一个重要因素。在花青素苷的生物合成过程中,二氢黄酮醇4-还原酶（DFR）是花青素苷生物合成下游途径中的第一个关键的酶。因此,DFR在高等植物花色的形成过程中发挥极其重要的作用,是形成花青素苷的一个非常重要的调控点。DFR对3种二氢黄酮醇底物具有选择特异性,但决定DFR底物特异性的分子机制目前仍不十分清楚。该文简单概述了花青素苷生物合成途径及其转录调控机制,并结合作者的工作重点综述了DFR的底物特异性以及克隆的DFR基因在植物基因工程中的应用。     

Control of anthocyanin biosynthesis pathway gene expression by eutypine,a toxin from Eutypa lata,in grape cell tissue cultures

Eutypine, 4-hydroxy-3-(3-methyl-3-butene-1-ynyl) benzaldehyde, is a toxin produced by Eutypa lata, the causal agent of Eutypa dieback in grapevine. The effect of the toxin on anthocyanin synthesis has been investigated in Vitis vinifera cv. Gamay cell cultures. At concentrations higher than 200 micromol/L, eutypine reduced anthocyanin accumulation in cells. The reduction in anthocyanin accumulation was proportional to the eutypine concentrations and HPLC analysis showed that eutypine affected the levels of all anthocyanins. The effect of eutypine application on the expression of five genes of the anthocyanin biosynthesis pathway, including chalcone synthase (CHS), flavonone-3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX), and UDP glucose-flavonoid 3-O-glucosyl transferase (UFGT) was determined. Expression of CHS, F3H, DFR and LDOXwas not affected by the addition of eutypine to grapevine cell cultures. In contrast, expression of the UFGT gene was dramatically inhibited by the toxin. These results suggest that in grapevine cell cultures, eutypine strongly affects anthocyanin accumulation by inhibiting UFGT gene expression. The mechanism of action of eutypine is discussed.     

Complementation of the Tomato anthocyanin without (aw) Mutant Using the Dihydroflavonol 4-Reductase Gene

We isolated the dihydroflavonol 4-reductase (DFR) gene from tomato (Lycopersicon esculentum) using a previously characterized cDNA as probe. Earlier studies had indicated that the DFR gene is present in tomato as a single gene located on chromosome 2 near the locus anthocyanin without (aw). Mutant alleles of the aw locus result in the complete absence of anthocyanin pigmentation throughout all stages of plant development. When the genomic DFR clone was introduced by Agrobacterium-mediated transformation into plants bearing the aw mutation, primary transgenic seedlings accumulated anthocyanins that could be observed while the plants were still in tissue culture and which continued to be observed as the plants matured. Progeny of self pollinated and backcrossed transgenic plants segregated for anthocyanin pigmentation, and Southern hybridization analyses indicated the presence of the DFR transgene exclusively in those plants with pigmentation. These data indicate that the aw locus likely corresponds to the structural gene for DFR and that DFR can be used as a visual, nondestructive, plant-derived marker gene for tomato.     

THF1 mutations lead to increased basal and wound-induced levels of oxylipins that stimulate anthocyanin biosynthesis via COI1 signaling in Arabidopsis

Mutants defective in chloroplast development or photosynthesis are liable to accumulate higher levels of anthocyanin in photo-oxidative stress. However, regulatory mechanisms of anthocyanin biosynthesi...     

Dihydroflavonol 4-reductase cDNA from non-anthocyanin-producing species in the Caryophyllales

Two types of red pigment, anthocyanins and betacyanins, never occur together in the same plant. Although anthocyanins are widely distributed in higher plants as flower and fruit pigments, betacyanins have replaced anthocyanins in the Caryophyllales. We isolated cDNAs encoding dihydroflavonol 4-reductase (DFR), which is the first enzyme committed to anthocyanin biosynthesis in the flavonoid pathway, from Spinacia oleracea and Phytolacca americana, plants that belong to the Caryophyllales. The deduced amino acid sequence of Spinacia DFR and Phytolacca DFR revealed a high degree of homology with DFRs of anthocyanin-producing plants. The DFR of carnation, an exception in the Caryophyllales that synthesizes anthocyanin, showed the highest level of identity. In the phylogenetic tree, Spinacia DFR and Phytolacca DFR clustered with the DFRs of anthocyanin-synthesizing dicots. Recombinant Spinacia and Phytolacca DFRs expressed in Escherichia coli convert dihydroflavonol to leucoanthocyanidin. The expression and function of DFR in spinach and pokeweed are discussed in relation to the molecular evolution of red pigment biosynthesis in higher plants.