Analysis ofcis-regulatory elements involved in the activation of a member of chalcone synthase gene family (PsChs1) in pea

Cis-regulatory elements involved in the activation of the plant defense-related gene encoding chalcone synthase 1 (PsChs1) in pea (Pisum sativum L.) were examined by transient transfection, gel mobility shift assay andin vitro DNase I-footprinting analysis. Transient transfection assay revealed that a 61 bp DNA fragment spanning from –242 to –182 ofPsChs1 was required for the maximal promoter activity and possibly involved in the enhancement of elicitor-mediated activation. Nuclear isolate from elicitor-treated pea epicotyl tissues contained some factor(s) that specifically bound to this DNA fragment to form a complex with low mobility (LMC, low mobility complex) in gel mobility shift assay. DNase I-footprinting analysis of LMC revealed that among three protected regions detected in a 61 bp DNA fragment, two regions contained identical AT-rich sequence, TAAAATACT. Site directed mutation in either or both identical sequences, TAAAATACT to TGGAATACT, resulted in the reduction or loss in the ability to form LMC. Detailed analysis of 61 bp DNA fragment demonstrated that the region from –242 to –226 containing promoter-distal TAAAATACT motif was imperative for the maximal elicitor-mediated activation ofPsChs1.     

QTL mapping for nodule number and common bacterial blight in Phaseolus vulgaris L.

A recently developed bean RFLP linkage map was used to identify genetic elements affecting quantitative trait loci (QTLs) in two contrasting common bean genotypes, BAT-93 and Jalo EEP558, under two levels of mineral nitrogen: low – 0.25 mM NH4NO3 and a high – 6 mM NH4NO3. QTLs affecting nodule number (NN) and response to Xanthomonas campestris bv. phaseoli, which causes common bacterial blight (CBB) were identified and mapped. Analyses of 70 F2-derived F3 families, using the F1, the two parents, and a nodulation-defective mutant (Nod-) inoculated with R. tropici UM1899 under both levels of N showed significant differences (P#60;0.0001) among the F3 families for NN.Under low N, three genomic regions influenced both traits, with seven linked markers. In three of the six regions influencing NN, higher NN was associated with the Jalo EEP-558 allele, whereas in only two regions was the BAT-93 allele associated with higher NN. One-way analysis of variance, with each marker as the independent variable and NN as the dependent variable, and interval mapping analysis identified four QTLs, which accounted for 45% of the total variation, and two additional QTLs near to yet unassigned loci. In linkage group D7, one QTL mapped to the same region as a QTL for CBB.Under high N, three additional regions were linked to NN, one where the BAT-93 allele was closely associated with CH18 (chitinase), and the others where the Jalo EEP-558 allele was associated with CHS (chalcone synthetase) and PAL-1 (phenylalanine ammonia lyase). Four regions for CBB were mapped adjacent to or in the same region as a QTL for NN. Thus, N showed dual and opposite effects on the expression of NN and CBB. Analysis of these RFLP markers revealed these hidden favorable alleles and can serve as an indirect selection tool to increase NN and resistance to CBB.     

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.     

Chalcone synthases from spinach (Spinacia oleracea L.)

The two chalcone-synthase forms from leaves ofSpinacia oleracea L. were purified to apparent homogeneity. Antibodies were raised against both proteins in rabbits. The specificity of the antibodies was tested using immunotitration, immunoblotting, and immunoelectrophoresis techniques. The antibodies exhibited exclusive specificity for chalcone synthase and did not discriminate between the two antigens. The homodimeric chalcone synthases had the same subunit molecular weight but differed in their apparent native molecular weights. The peptide maps indicated extensive homology between the proteins. Chalcone-synthase activity was not detected in isolated spinach chloroplasts. Both enzyme forms were present in spinach cell-suspension cultures in which they were induced by light.Abbreviations DEAE diethylaminoethyl - DTE 1,4-dithioerythritol - EDTA ethylenediaminetetraacetic acid - HPLC high-performance liquid chromatography - IgG immunoglobulin G - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis Parts of the results were presented at the 14^th International Botanical Congress at Berlin in July 1987     

Synthesis,Biological Activity and Action Mechanism Study of Novel Chalcone Derivatives Containing Malonate

A series of novel chalcone malonate derivatives were synthesized and their antibacterial and antiviral activities were evaluated. All target compounds were characterized by spectral data. The results of antimicrobial bioassay showed that one compound (diethyl [3‐(naphthalen‐2‐yl)‐1‐(3‐nitrophenyl)‐3‐oxopropyl]propanedioate) showed excellent antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo), with an EC₅₀ value of 10.2 μg/mL, which is significantly superior to bismerthiazol (71.7 μg/mL) and thiodiazole copper (97.8 μg/mL). At the same time, the mechanism of two compounds was confirmed by scanning electron microscopy. In addition, another compound (diethyl [3‐(naphthalen‐2‐yl)‐1‐(4‐nitrophenyl)‐3‐oxopropyl]propanedioate) showed significant curative activity to tobacco mosaic virus, with a value of 74.3 %, which was superior to 53.3 % of ningnanmycin. The results of microscale thermophoresis also showed that the Kd value of the combination of two compounds with the coat protein of tobacco mosaic virus was 0.211 and 0.166 μmol/L, which was better than 0.596 μmol/L of ningnanmycin. At the same time, the molecular docking of two compounds with tobacco mosaic virus‐coat protein shows that the compound is well embedded in the pocket between the two subunits of tobacco mosaic virus‐coat protein. These results show that chalcone derivatives containing malonate group can be considered as activators in the design of antibacterial and antiviral agents.     

Synthesis and biological evaluation of alpha-bromoacryloylamido indolyl pyridinyl propenones as potent apoptotic inducers in human leukaemia cells

The combination of two pharmacophores into a single molecule represents one of the methods that can be adopted for the synthesis of new anticancer molecules. To investigate the influence of the position of the pyridine nitrogen on biological activity, two different series of α-bromoacryloylamido indolyl pyridinyl propenones 3a–h and 4a–d were designed and synthesized by a pharmacophore hybridization approach and evaluated for their antiproliferative activity against a panel of six human cancer cell lines. These hybrid molecules were prepared to combine the α-bromoacryloyl moiety with two series of indole-inspired chalcone analogues, possessing an indole derivative and a 3- or 4-pyridine ring, respectively, linked on either side of 2-propen-1-one system. The structure-activity relationship was also investigated by the insertion of alkyl or benzyl moieties at the N-1 position of the indole nucleus. We found that most of the newly synthesized displayed high antiproliferative activity against U-937, MOLT-3, K-562, and NALM-6 leukaemia cell lines, with one-digit to double-digit nanomolar IC₅₀ values. The antiproliferative activities of 3-pyridinyl derivatives 3f–h revealed that N-benzyl indole analogues generally exhibited lower activity compared to N-H or N-alkyl derivatives 3a–b and 3c–e, respectively. Moreover, cellular mechanism studies elucidated that compound 4a induced apoptosis along with a decrease of mitochondrial membrane potential and activated caspase-3 in a concentration-dependent manner.     

Chalcone Synthase Localization in Early Stages of Plant Development. I. Immunohistochemical Use of Plasmolysis for Localizing the Enzyme in Epidermal Cell Cytoplasm of Illuminated Buckwheat Hypocotyls

Immunohistochemical methods combined with progressive plasmolysis were used to localize chalcone synthase (CHS), an important enzyme for plant metabolism of aromatics in hypocotyls of illuminated buckwheat (Fagopyrum esculentum M) seedlings. Illumination of etiolated seedlings with white light results in anthocyanin synthesis in the epidermal layer of the hypocotyl. Anthocyanin-containing epidermal peels, after fixation for 30 min in 4% paraformaldehyde, 2.5% glutaraldehyde, 0.1% caffeine, were treated with a specific rabbit anti-buckwheat CHS antibody and a 20 nm goat anti-rabbit IgG gold conjugate. CHS is specifically shown in epidermal cells as pink to dark red deposits. Progressive plasmolysis combined with our immunohistochemical method showed that CHS was located exclusively in the cytoplasm of the epidermal cells of buckwheat hypocotyls except for the guard cells, which contained no detectable CHS.     

Molecular characterization and expression of alfalfa (Medicago sativa L.) flavanone-3-hydroxylase and dihydroflavonol-4-reductase encoding genes

Flavonoids are plant phenolic compounds involved in leguminous plant-microbe interactions. Genes implied in the central branch (chalcone synthase (CHS), chalcone isomerase (CHI)) or in the isoflavonoid branch of the flavonoid biosynthesis pathway have been characterized in Medicago sativa. No information is available to date, however, on genes whose products are involved in the synthesis of other types of flavonoids. In this paper we present the genomic organization as well as the nucleotide sequence of one flavanone-3-hydroxylase (F3H) encoding gene of M. sativa, containing two introns and exhibiting 82–89% similarity at the amino acid level to other F3H proteins. This is the first report on the gennomic organization of a f3h gene so far. We present also the sequence of a partial dihydroflavonol-4-reductase (DFR) M. sativa cDNA clone. Southern blot experiments indicated that f3h and dfr genes are each represented by a single gene within the tetraploid genome of M. sativa. By a combination of Northern blot and RT-PCR analysis, we showed that both f3h and dfr genes are expressed in flowers, nodules and roots, with a pattern distinct from chs expression. Finally, we show that dfr is expressed in M. sativa leaves whereas f3h is not. The role played by these two genes in organs other than flowers remains to be determined.