苦荞转录因子FtMYBF的克隆、亚细胞定位及表达分析

R2R3-MYB转录因子SG7亚家族成员在植物黄酮醇生物合成中具有极其重要的调控作用.探究苦荞中SG7 R2R3-MYB转录因子在黄酮醇生物合成中的功能,为苦荞黄酮醇生物合成的分子调控机制研究奠定基础.采用RT-PCR技术从苦荞中克隆到一个前期经转录组与代谢组联合分析鉴定到的SG7 R2R3-MYB转录因子,命名为Ft...     

Differential combinatorial interactions of <Emphasis Type="Italic">cis</Emphasis>-acting elements recognized by R2R3-MYB,BZIP, and BHLH factors control light-responsive and tissue-specific activation of phenylpropanoid biosynthesis genes

Chalcone synthase (CHS), chalcone flavanone isomerase (CFI), flavanone 3-hydroxylase (F3H) and flavonol synthase (FLS) catalyze successive steps in the biosynthetic pathway leading to the production of flavonols. We show that in Arabidopsis thaliana all four corresponding genes are coordinately expressed in response to light, and are spatially coexpressed in siliques, flowers and leaves. Light regulatory units (LRUs) sufficient for light responsiveness were identified in all four promoters. Each unit consists of two necessary elements, namely a MYB-recognition element (MRE) and an ACGT-containing element (ACE). C1 and Sn, a R2R3-MYB and a BHLH factor, respectively, known to control tissue specific anthocyanin biosynthesis in Z. mays, were together able to activate the AtCHS promoter. This activation of the CHS promoter required an intact MRE and a newly identified sequence designated R response element (RRE ^AtCHS) containing the BHLH factor consensus binding site CANNTG. The RRE was dispensable for light responsiveness, and the ACE was not necessary for activation by C1/Sn. These data suggest that a BHLH and a R2R3-MYB factor cooperate in directing tissue-specific production of flavonoids, while an ACE-binding factor, potentially a BZIP, and a R2R3-MYB factor work together in conferring light responsiveness.     

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.     

Accumulation of flavonols in response to ultraviolet-B irradiation in soybean is related to induction of flavanone 3-beta-hydroxylase and flavonol synthase

There are several branch points in the flavonoid synthesis pathway starting from chalcone. Among them, the hydroxylation of flavanone is a key step leading to flavonol and anthocyanin. The flavanone 3-beta-hydroxylase (GmF3H) gene was cloned from soybean (Glycine max cultivar Sinpaldal) and shown to convert eriodictyol and naringenin into taxifolin and dihydrokaempferol, respectively. The major flavonoids in this soybean cultivar were found by LC-MS/MS to be kamepferol O-triglycosides and O-diglycosides. Expression of GmF3H and flavonol synthase (GmFLS) was induced by ultraviolet-B (UV-B) irradiation and their expression stimulated accumulation of kaempferol glycones. Thus, GmF3H and GmFLS appear to be key enzymes in the biosynthesis of the UV-protectant, kaempferol.     

Functional expression of a P450 flavonoid hydroxylase for the biosynthesis of plant-specific hydroxylated flavonols in Escherichia coli

Flavonols are plant polyphenolic compounds that belong to the class of molecules collectively known as flavonoids. Because of their demonstrated health benefits towards a wide array of human pathological conditions, a great interest has emerged for their biosynthesis from well-characterized microbial hosts. We present the functional expression in Escherichia coli of a plant P450 flavonoid 3', 5'-hydroxylase (F3'5'H) as a fusion protein with a P450 reductase. This expression allowed metabolic engineering of E. coli to produce the flavonol kaempferol and the 3', 4' B-ring hydroxylated flavonol quercetin from the p-coumaric acid precursor by simultaneously co-expressing the fusion protein with 4-coumaroyl:CoA-ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3beta-hydroxylase (FHT) and flavonol synthase (FLS). Biosynthesis of the B-ring tri-hydroxylated flavonol myricetin from the engineered strains was accomplished when flavanones rather than phenylpropanoid acids were used as precursor molecules. Cultivation of the recombinant strains in rich medium increased the synthesis of all flavonoids with the exception of myricetin. The present work opens the possibility of the future production of several other hydroxylated flavonoid molecules in E. coli.     

Molecular characterization of 60 isolated wheat MYB genes and analysis of their expression during abiotic stress

The proteins of the MYB superfamily play central roles in developmental processes and defence responses in plants. Sixty unique wheat MYB genes that contain full-length cDNA sequences were isolated. These 60 genes were grouped into three categories, namely one R1R2R3-MYB, 22 R2R3-MYBs, and 37 MYB-related members. The sequence composition of the R2 and R3 repeats was conserved among the 22 wheat R2R3-MYB proteins. Phylogenetic comparison of the members of this superfamily among wheat, rice, and Arabidopsis revealed that the putative functions of some wheat MYB proteins were clustered into the Arabidopsis functional clades. Tissue-specific expression profiles showed that most of the wheat MYB genes were expressed in all of the tissues examined, suggesting that wheat MYB genes take part in multiple cellular processes. The expression analysis during abiotic stress identified a group of MYB genes that respond to one or more stress treatments. The overexpression of a salt-inducible gene, TaMYB32, enhanced the tolerance to salt stress in transgenic Arabidopsis. This study is the first comprehensive study of the MYB gene family in Triticeae.     

拟南芥R2R3-MYB类转录因子在环境胁迫中的作用

MYB转录因子是植物转录因子中最大的家族之一,以含有保守的MYB结构域为共同特征,分为三个亚族（R1／2-MYB、R2R3-MYB和R1R2R3-MYB）,其中含有两个MYB结构域的R2R3-MYB成员最多,广泛参与植物次生代谢调控、细胞形态发生、胁迫应答、分生组织形成及细胞周期控制等。近年来,R2R3-MYB在植物逆境胁迫中的作用引起了广泛关注,本文综述了拟南芥R2R3-MYB蛋白在环境胁迫响应中作用的研究进展。