Activities of growth inhibitors isolated from light-grown dwarf pea shoots

The growth inhibitory activities of 6 endogenous growth inhibitors isolated from light-grown dwarf peas (Pisum sativum cv. Progress No. 9) were examined in the epicotyl of dark-grown seedlings of the same cultivar in the dark in order to examine the possible contribution of these compounds to the growth inhibition brought about by red light. The activities of these natural inhibitors, including two A-2 and A-2 of as yet undetermined structure, were compared with those of synthetic growth retardants and benzyladenine. Samples were applied directly into the epicotyls via a glass capillary tube. In 24-h tests doses for a 25% inhibition (I₂₅) were: A-2, 4.3 × 10^-2: cis-xanthoxin, 1.2 × 10^-1 ; A-2, 1.6 × 10^-1; trans-xanthoxin, 1.2; R,S-dihydromaleimide, 3.5 × 10² and pisatin, 4.0 × 10² nmol plant^-1 . In 72-h tests, I₂₅'s were: benzyladenine, 1.5; AMO-1618 (ammonium-(5-hydroxycarvacryl)-trimethylchloride piperidine carboxylate), 2.4; R,S-dihydromaleimide, 4.0 × 10² and CCC (chlorocholine chloride), 1.1 × 10³ nmol plant^-1. -D-Glucosyl-R-dihydromaleimide had no activity at all. Benzyladenine caused the thickening as well as elongation inhibition of the epicotyls of intact plants. The possible involvement of A-2 and in the red light growth inhibition of dwarf peas is discussed.Abbreviations AMO-1618 ammonium-(5-hydroxycarvacryl)-trimethylchloride piperidine carboxylate - CCC chlorocholine chloride - G-DHMD -D-glucosyl-R-dihydromaleimide - I₂₅ dose required for a 25% growth inhibition - R red light author for correspondence     

Occurrence of juvabione-type and epijuvabione-type sesquiterpenoids in Abies alba

The petrol-soluble fractions from the branchwood of four Abies alba trees were examined. Only two trees contained sufficient amounts of ‘juvabione-type’ insect juvenile hormone analogues for isolation and characterization. The first contained juvabione (4R, 1′R), 4′-dehydrojuvabione (4R, 1′R) and its 4R, 1′S diastereomer in a ratio of 3:1, and juvabiol (4R, 1′R, 3′S), isojuvabiol (4R, 1′R, 3′R) and epijuvabiol (4R, 1′S, 3′S) in an approximate ratio of 7:3:2. 4′-Dehydroepijuvabione (4R, 1′S) was the only ‘juvabione-type’ compound ioslated from the second tree. If it is accepted that juvabione and epijuvabione are enzymatically reduced forms of dehydrojuvabione and dehydroepijuvabione, respectively; then for these two A. alba our results indicate that only one enzyme which is specific for R chirality at C-1′ is present, since epijuvabione is not observed.     

Isolation and structural elucidation of cucurbitaxanthin a and b from pumpkin cucurbita maxima

Two new carotenoids, cucurbitaxanthin A [(3S,5R,6,R3′R)-3,6-epoxy-5,6-dihydro-β,β-carotene-5,3′-diol] and cucurbitaxanthin B [(3S,5R,6R,3′S,5′R,6′S)-3,6,5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β-β-carotene-5,3′-diol] have been isolated from the pumpkin Cucurbita maxima.     

Preparation, properties and crystal structure of two isomers of R,R,S,S- and R,S,R,S-[chloro(1,3,10,12,16,19-hexaazatetracyclo[17,3,1,1,0]tetracosane)copper(II)]

Two isomers (R,S,R,S- and R,R,S,S-) of five coordinate complex [Cu(L)Cl]⁺ have been separated and characterised. These two isomers have significantly different spectrochemical and electrochemical properties. Absorption maximum of R,S,R,S-[Cu(L)Cl]⁺ shifts to longer wavelength and its reduction potential shifts to more positive direction comparing those of R,R,S,S-[Cu(L)Cl]⁺. R,S,R,S-[Cu(L)Cl]⁺ is significantly distorted to trigonal-bipyramidal structure, whereas R,R,S,S-[Cu(L)Cl]⁺ retains almost square-planar geometry. The average bond distance of Cu-N in basal plane of R,S,R,S-[Cu(L)Cl]⁺ is longer by 0.024 Å than that of R,R,S,S-[Cu(L)Cl]⁺, whereas the bond distance of Cu-Cl in former is shorter by 0.200 Å than that in latter. The isolated square-planar complexes of R,R,S,S- and R,S,R,S-[Cu(L)](ClO₄)₂ are converted to the R,R,S,S- and R,S,R,S-[Cu(L)Cl]⁺ by the addition of Cl⁻ in nitromethane solution with the rate constants, k=1.70 (±0.02) and 8.31 (±0.07) M⁻¹ s⁻¹, respectively.     

Separating the contributions of vascular anatomy and blood viscosity to peripheral resistance and the physiological implications of interspecific resistance variation in amphibians

Amphibian pulmonary and systemic vascular circuits are arranged in parallel, with potentially important consequences for resistance (R) to blood flow. The contribution of the parallel anatomic arrangement to total vascular R (R _T), independent of blood viscosity, is unknown. We measured pulmonary (R _P) and systemic (R _S) vascular R with an in situ Ringer’s solution perfusion technique using anesthetized anuran and urodele species to determine: (1) relative contributions of vascular anatomy and blood viscosity to R _T; (2) distensibility index (%Δ flow kPa^?1) of the pulmonary and systemic vascular circuits; and (3) interspecific correlates of variation in these parameters with red blood cell size, cardiac power output, and aerobic capacities. R _P was lower than R _S in anurans, while R _P of the urodeles was greater than R _S and significantly greater than anuran R _P. Anuran R _T was lowest and did not vary interspecifically, whereas urodele R _T was significantly greater than anuran, and varied interspecifically. Pulmonary and systemic circuit distensibility differences may explain cardiac shunt patterns in toads with changes in cardiac output from rest to activity. When blood viscosity was taken into account, vascular resistance accounted for about 25 % of R _T while blood viscosity accounted for the remaining 75 %. Owing to lower R _T, terrestrial anuran species required lower cardiac power outputs when moving fluid through their vasculature compared to aquatic species. These results indicate that physical characteristics of the vasculature can account for interspecific differences in cardiovascular physiology and suggest a co-evolution of cardiac and vascular anatomy among amphibians.     

The effect of pyramiding Phytophthora infestans resistance genes R Pi-mcd1 and R Pi-ber in potato

Despite efforts to control late blight in potatoes by introducing R _pi -genes from wild species into cultivated potato, there are still concerns regarding the durability and level of resistance. Pyramiding R _pi -genes can be a solution to increase both durability and level of resistance. In this study, two resistance genes, R _Pi-mcd1 and R _Pi-ber , introgressed from the wild tuber-bearing potato species Solanum microdontum and S. berthaultii were combined in a diploid S. tuberosum population. Individual genotypes from this population were classified after four groups, carrying no R _pi -gene, with only R _Pi-mcd1 , with only R _Pi-ber , and a group with the pyramided R _Pi-mcd1 and R _Pi-ber by means of tightly linked molecular markers. The levels of resistance between the groups were compared in a field experiment in 2007. The group with R _Pi-mcd1 showed a significant delay to reach 50% infection of the leaf area of 3 days. The group with R _Pi-ber showed a delay of 3 weeks. The resistance level in the pyramid group suggested an additive effect of R _Pi-mcd1 with R _Pi-ber . This suggests that potato breeding can benefit from combining individual R _pi -genes, irrespective of the weak effect of R _Pi-mcd1 or the strong effect of R _Pi-ber .     

Host–pathogen interaction between Phytophthora infestans and Solanum tuberosum following exposure to short and long daylight hours

The influence of short and long day length on the expression of qualitative and quantitative resistance to Phytophthora infestans in potato was studied. The incompatible interaction was tested for available set of isolates avirulent in greenhouse conditions to potato Black’s differentials possessing the genes: R2, R5, R6, R8, R9, R10, and standard potato cultivar Tarpan (no known R gene). The avirulent isolates either were completely avirulent regardless of plant growing conditions, or they infected leaflets of these differentials more frequently when plants were exposed previously to short day conditions than to long day conditions. This study highlights the importance of day length, among many other factors which are controlled, in testing the expression of the virulence of P. infestans isolates. In compatible interactions, when quantitative resistance was evaluated in differentials with gene R1, R3, R4, R7, R11, and potato cultivar Craigs Royal (no known R gene), stronger infection expressed by lesion growth rate, as well as stronger sporulation, were observed on potato leaflets of plants exposed to short day for 6–7 weeks before inoculation. The analysis of variance revealed a significant contribution to variation in lesion growth rate of day length, genotype, as well as day length by genotype interaction. Significant influence of isolate, and genotype, but not day length, on the expression of the incubation period was found. The results indicate the necessity of evaluating components of partial resistance present in potato lines used in breeding potato resistant to P. infestans in destined day length growing conditions.     

Absolute configuration of heteroxanthin and diadinoxanthin

The absolute configurations of heteroxanthin ((3S,5S,6S,3′R)- 7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,5,3′,6′-tetrol) ex Euglena gracilis and of diadinoxanthin ((3S,5R,6S,3′R)-5,6-epoxy-7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,3′-diol) from the same source have been established by chemical reactions, hydrogen bonding studies, ¹H NMR and CD. Two previously unknown carotenoids (artefacts?) from Trollius europaeus, assigned the structures (3S,5S,6S,3′S,5′R,6′R)-6,7-didehydro-5,6,5′,6′-tetrahydro-β,β -carotene-3,5,6,3′,5′-pentol and its 5R epimer, served as useful models.     

Synthesis and acetylcholinesterase inhibitory activities of tabersonine derivatives

Tabersonine, the main alkaloid in Voacanga seeds, was used as a lead compound to semi-synthesize tabersonine derivatives. In total, 13 compounds, containing 10 novel tabersonine derivatives, were synthesized by introducing substituent groups R₁–R₅. The acetylcholinesterase (AChE) inhibitory activities of tabersnonine derivatives were evaluated using Ellman’s method. Among them, compound (7) showed the highest AChE inhibitory activity with the IC₅₀ value was 5.32 μM. The substituent groups R₁–R₅ showed different influences on the AChE inhibitory activities of tabersonine derivatives. The AChE inhibitory activities of tabersonine derivatives increased with the introduction of group R₁ and/or combined groups R₃, R₄, while decreased with the introduction of group R₅. And the group R₂ showed no significant influence on the AChE inhibitory activities of tabersonine derivatives.     

In Situ CO2 Efflux from Leaf Litter Layer Showed Large Temporal Variation Induced by Rapid Wetting and Drying Cycle

We performed continuous and manual in situ measurements of CO₂ efflux from the leaf litter layer (R _LL) and water content of the leaf litter layer (LWC) in conjunction with measurements of soil respiration (R _S) and soil water content (SWC) in a temperate forest; our objectives were to evaluate the response of R _LL to rainfall events and to assess temporal variation in its contribution to R _S. We measured R _LL in a treatment area from which all potential sources of CO₂ except for the leaf litter layer were removed. Capacitance sensors were used to measure LWC. R _LL increased immediately after wetting of the leaf litter layer; peak R _LL values were observed during or one day after rainfall events and were up to 8.6-fold larger than R _LL prior to rainfall. R _LL declined to pre-wetting levels within 2–4 day after rainfall events and corresponded to decreasing LWC, indicating that annual R _LL is strongly influenced by precipitation. Temporal variation in the observed contribution of R _LL to R _S varied from nearly zero to 51%. Continuous in situ measurements of LWC and CO₂ efflux from leaf litter only, combined with measurements of R _S, can provide robust data to clarify the response of R _LL to rainfall events and its contribution to total R _S.     

Diamidato-bis(diphenylphosphino) platinum(II) complexes: Synthesis, characterization, and reactivity in the presence of acid

The reaction of Pt(COD)Cl₂, where COD is 1,5-cyclooctadiene, with one equivalent of a diamidato-bis(phosphino) Trost ligand ((R,R)-2 = N,N′-bis(2-diphenylphosphino-1-benzoyl)-(1R,2R)-1,2-diaminocyclohexane, (R,R)-3 = N,N′-bis(2-diphenylphosphino-1-naphthoyl)-(1R,2R)-1,2-diaminocyclohexane, or (±)-4 = N,N′-bis(2-diphenylphosphino-1-benzoyl)-1,2-bis(aminobenzene)) in the presence of base afforded square planar diamidato-bis(phosphino) platinum(II) complexes (R,R)-2-Pt, (R,R)-3-Pt, (±)-4-Pt. Characterization of all complexes included the solution and solid state structure determination of each complex based on multinuclear NMR and X-ray analyses, respectively. Stability of the complexes in acid was examined on addition of HCl to (R,R)-2-Pt in chloroform and compared to the unreactive nature of the similar diamidato-bis(phosphino) complex 1-Pt (1 = 1,2-bis-N-[2′-(diphenylphosphino)benzoyl]diamino-benzene) in the presence of acid. Protonation of the bound amidato nitrogen atoms of (R,R)-2-Pt was observed along with decoordination of the nitrogen atoms from the platinum(II) center producing (R,R)-2-PtCl₂ in quantitative yield by NMR analysis. Confirmation of the product was made on comparison of the NMR spectra to that of authentic (R,R)-2-PtCl₂ prepared on reaction of Pt(COD)Cl₂ with (R,R)-2 in CH₂Cl₂ and characterized by single-crystal X-ray diffraction analysis and NMR spectroscopy. Results add to the knowledge of rich coordination chemistry of bis(phosphino) ligands with late transition metals, metal-amidato chemistry, and has implications in catalysis.     

MC1R Is a Prognostic Marker and Its Expression Is Correlated with MSI in Colorectal Cancer

Melanocortin 1 receptor (MC1R) is thought to be a marker of poor prognosis and a potential target for the treatment of melanoma. Studies have found that MC1R promotes several tumor behaviors, including cell proliferation and differentiation, pigment formation, and genome damage repair. Some single-nucleotide polymorphisms (SNPs) of MC1R are involved in the occurrence and development of melanoma. A few studies have reported a relationship between MC1R and colorectal cancer (CRC). In this research, our objective was to examine MC1R expression and MC1R SNPs and investigate their correlation with the clinicopathological features of human CRC tissues. We evaluated MC1R mRNA expression by performing bioinformatic analyses on human CRC expression datasets. We used Western blotting and RT-qPCR to compare MC1R expression in CRC tissues with that in normal tissues, and MC1R SNPs in CRC tissues were detected by PCR-direct sequencing (DS). The expression of MC1R was significantly decreased in CRC tissues compared with normal tissue, and its expression was negatively associated with P53 expression, MLH1 expression, and PMS2 expression, and high MC1R expression was significantly associated with microsatellite instability (MSI). MC1R SNPs were also associated with the clinicopathological characteristics of CRC; for example, the rs2228479 locus genotype was correlated with Ki67 status, and the rs885479 locus genotype was correlated with age and T stage. In conclusion, MC1R plays a crucial role in the progression of CRC and may be a marker of poor prognosis in CRC.     

Alkaloids of stem and rootbark of Tabernaemontana dichotoma

During chemical investigation for compounds possessing biological activity in the stem and rootbark of Tabernaemontana dichotoma, 22 alkaloids were isolated. Ten monomeric alkaloids were identified, viz. (?)-apparicine, coronaridine, 3-oxocoronaridine, 3-ketopropylcoronaridine, 19R-heyneanine, 3-ketopropyl-19R-heyneanine, ibogamine, isomethuenine, perivine and vobasine. Two of the monomeric alkaloids isolated were new, one was identified as 3,19R-oxidocoronaridine and the other one is not yet identified. The other ten alkaloids isolated were dimeric compounds, three were identified as tabernamine, voacamine and 3′R/S-hydroxyvoacamine. Five of the dimers were new alkaloids related to tabernamine and ervahanine type structures and identified as 3′R/S-hydroxytabernamine, 3′R/S-hydroxy-N₄-demethyltabernamine, N₄-demethyltabernamine and 3′R/S-hydroxy-N₄-demethytervahanine A and B. The remaining two alkaloids are partially characterized.     

Reaction mechanism of 5,8-linoleate diol synthase, 10R-dioxygenase,and 8,11-hydroperoxide isomerase of Aspergillus clavatus

Aspergilli express fusion proteins of an animal haem peroxidase domain with fatty acid dioxygenase (DOX) activity (∼ 600 amino acids) and a functional or non-functional hydroperoxide isomerase/cytochrome P450 domain (∼ 500 amino acids with EXXR and GPHXCLG motifs). 5,8-Linoleate diol synthases (LDS; ppoA) and 10R-DOX (ppoC) of Aspergillusnidulans and A. fumigatus belong to this group. Our objective was to determine the oxylipins formed from linoleic acid by A. clavatus and their mechanism of biosynthesis. A. clavatus oxidized linoleic acid to (8R)-hydroperoxylinoleic acid (8R-HPODE), (10R)-hydroperoxy-8(E),12(Z)-octadecadienoic acid (10R-HPODE), and to (5S,8R)-dihydroxy- and (8R,11S)-dihydroxylinoleic acids (DiHODE) as major products. This occurred by abstraction of the pro-S hydrogen at C-8 and antarafacial dioxygenation at C-8 or at C-10 with double bond migration. 8R-HPODE was then isomerized to 5S,8R-DiHODE and to 8R,11S-DiHODE by abstraction of the pro-S hydrogens at C-5 and C-11 of 8R-HPODE, respectively, followed by suprafacial oxygenation. The genome of A. clavatus codes for two enzymes, which can be aligned with > 65% amino acid identity to 10R-DOX and 5,8-LDS, respectively. The 5,8-LDS homologue likely forms and isomerizes 8R-HPODE to 5S,8R-DiHODE. A third gene (ppoB) codes for a protein which carries a serine residue at the cysteine position of the P450 motif. This Cys to Ser replacement is known to abolish P450 2B4 catalysis and the hydroperoxide isomerase activity of 5,8-LDS, suggesting that ppoB of A. clavatus may not be involved in the biosynthesis of 8R,11S-DiHODE.     

三种温带树种叶片呼吸的时间动态及其影响因子

为认知叶片呼吸(RL)的季节变化格局及其影响因子,以东北东部山区3个主要树种(红松Pinus koraiensis、樟子松P.sylvestris var.mongolica和白桦Betula platyphylla)为对象,采用红外气体分析法在2011年生长季(常绿树4月至10月;落叶树6月至9月)测定了自然条件下叶片气体交换及其相关生理特征的季节变化,探索了RL与空气温度(Tair)和相关叶片特征之间的关系.结果表明:红松和樟子松基于叶面积的RL(RL-area)表现为生长季初期和末期较大,而白桦RL-area则随生长季进程而逐渐减小.在生长季中,RL-area与叶片总光合之比的时间动态明显.红松、樟子松RL-area与Tair关系显著,而白桦RL-area与Tair关系不显著;但3种树种基于叶质量的RL(RL-mass)与Tair均呈显著的指数函数关系.叶片特征(包括可溶性糖、淀粉、氮、比叶面积等参数)也有明显的季节变化.影响RL的叶片特征参数因树种而异,其中可溶性糖浓度对3种树种的RL均有显著影响.可见,RL的季节变化格局受树木的生长节律、温度和叶片特征的联合控制.     

Occurrence and chirality of oscillaxanthin

The quantitative carotenoid composition of natural blooms of Oscillatoria rubescens and O. agardhii is reported and compared with previous isolations. Chemical or enzymatic conversion of oscillaxanthin to the chiral aglycone failed. CD-correlation of oscillaxanthin hexaacetate with (2S,2′S)-bacterioruberin, (2′R)-plectaniaxanthin and (2′R)-plectaniaxanthin-2′-β-D-glucoside tetraacetate support the 2R,2′R-configuration for oscillaxanthin.     

Mechanism of 2,3-butanediol stereoisomer formation in Klebsiella pneumoniae

Klebsiella pneumoniae is known to produce meso-2,3-butanediol and 2S,3S-butanediol, whereas 2R,3R-butanediol was detected in the culture broth of K. pneumoniae CGMCC 1.6366. The ratio of 2R,3R-butanediol to all isomers obtained using glycerol as the carbon source was higher than that obtained using glucose as the carbon source. Therefore, enzymes involved in glycerol metabolism are likely related to 2R,3R-butanediol formation. In vitro reactions show that glycerol dehydrogenase catalyzes the stereospecific conversion of R-acetoin to 2R,3R-butanediol and S-acetoin to meso-2,3-butanediol. Butanediol dehydrogenase exhibits high (S)-enantioselectivity in ketone reduction. Genes encoding glycerol dehydrogenase, α-acetolactate decarboxylase, and butanediol dehydrogenase were individually disrupted in K. pneumoniae CGMCC 1.6366, and the 2,3-butanediol synthesis characteristics of these mutants were investigated. K. pneumoniae ΔdhaD lost the ability to synthesize 2R,3R-butanediol. K. pneumoniae ΔbudA showed reduced 2R,3R-butanediol synthesis. However, K. pneumoniae ΔbudC produced a high level of 2R,3R-butanediol, and R-acetoin was accumulated in the broth. The metabolic characteristics of these mutants and in vitro experiment results demonstrated the mechanism of the 2,3-butanediol stereoisomer synthesis pathway. Glycerol dehydrogenase, encoded by dhaD, exhibited 2R,3R-butanediol dehydrogenase activity and was responsible for 2R,3R-butanediol synthesis from R-acetoin. This enzyme also contributed to meso-2,3-butanediol synthesis from S-acetoin. Butanediol dehydrogenase, encoded by budC, was the only enzyme that catalyzed the conversion of diacetyl to S-acetoin and further to 2S,3S-butanediol.     

Configurational studies on red algae carotenoids

The configurations of (6′R)-β,ε-carotene, (3′R,6′R)-β,ε-caroten-3′-ol (α-cryptoxanthin), (3R,3′R,6′R)-β,ε-carotene-3,3′-diol (lutein), (3R)-β,β-caroten-3-ol (β-cryptoxanthin), (3R,3′R)-β,β-carotene-3,3′-diol (zeaxanthin) and all-trans (3S,5R,6S,3′R)-5,6-epoxy-5,6-dihydro-β,β-carotene-3,3′-diol (antheraxanthin) were established by CD and ¹H NMR studies. The red algal carotenoids consequently possessed chiralities at each chiral center (C-3, C-5, C-6, C-3′, C-6′), corresponding to the chiralities established for the same carotenoids in higher plants. Two post mortem artifacts from Erythrotrichia carnea were assigned the chiral structures (3S,5R,8R,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8R)-mutatoxanthin] and (3S,5R,8S,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8S)-mutatoxanthin]. This is the first well documented report of a naturally occurring β,ε-caroten-3′-ol (¹H NMR, CD, chemical derivatization).     

Lipase-catalyzed enantioselective synthesis of (R,R)-lactide from alkyl lactate to produce PDLA (poly D-lactic acid) and stereocomplex PLA (poly lactic acid)

R-lactide, a pivotal monomer for the production of poly (D-lactic acid) (PDLA) or stereocomplex poly (lactic acid) (PLA) was synthesized from alkyl (R)-lactate through a lipase-catalyzed reaction without racemization. From among several types of lipase, only lipase B from Candida antarctica (Novozym 435; CAL-B) was effective in the reaction that synthesized (R,R)-lactide. Enantiopure (R,R)-lactide, which consisted of over 99% enantiomeric excess, was synthesized from methyl (R)-lactate through CAL-B catalysis. Removal of the methanol by-product was critical to obtain a high level of lactide conversion. The (R,R)-lactide yield was 56% in a reaction containing 100 mg of Novozym 435, 10 mM methyl (R)-lactate and 1500 mg of molecular sieve 5 A in methyl tert-butyl ether (MTBE). The important monomer (R,R)-lactide that is required for the production of the widely recognized bio-plastic PDLA and the PLA stereocomplex can be obtained using this novel synthetic method.