Lipoxygenase from the leaves of wheat grown under different water supply conditions

Lipoxygenase (LOG) in protein fractions isolated from the leaves of substituted wheat lines was investigated. Three molecular forms of the enzyme were detected. A water deficiency caused the induction of a membrane-bound form (mLOG) and resulted in a decrease in the activity of "soluble" enzymes (s1LOG) and (s2LOG) in most genotypes. A correlation analysis demonstrated the dependence between the level of enzymatic activity and indices of resistance to drought. A genetic control of the s 1 LOG and s2LOG activity at an optimal water supply level was associated with chromosomes 1A, 1D, 3A, 5A, 5B, and 5D, while under the conditions of the modeled soil drought, it was associated with chromosomes 1B and 1D.     

Functional Analyses of LONELY GUY Cytokinin-Activating Enzymes Reveal the Importance of the Direct Activation Pathway in Arabidopsis

Cytokinins play crucial roles in diverse aspects of plant growth and development. Spatiotemporal distribution of bioactive cytokinins is finely regulated by metabolic enzymes. LONELY GUY (LOG) was previously identified as a cytokinin-activating enzyme that works in the direct activation pathway in rice (Oryza sativa) shoot meristems. In this work, nine Arabidopsis thaliana LOG genes (At LOG1 to LOG9) were predicted as homologs of rice LOG. Seven At LOGs, which are localized in the cytosol and nuclei, had enzymatic activities equivalent to that of rice LOG. Conditional overexpression of At LOGs in transgenic Arabidopsis reduced the content of N⁶-(Δ²-isopentenyl)adenine (iP) riboside 5′-phosphates and increased the levels of iP and the glucosides. Multiple mutants of At LOGs showed a lower sensitivity to iP riboside in terms of lateral root formation and altered root and shoot morphology. Analyses of At LOG promoter:β-glucuronidase fusion genes revealed differential expression of LOGs in various tissues during plant development. Ectopic overexpression showed pleiotropic phenotypes, such as promotion of cell division in embryos and leaf vascular tissues, reduced apical dominance, and a delay of leaf senescence. Our results strongly suggest that the direct activation pathway via LOGs plays a pivotal role in regulating cytokinin activity during normal growth and development in Arabidopsis.     

Leaf dehydroascorbate reductase and catalase activity is associated with soil drought tolerance in bread wheat

A number of morphological, physiological and phenological traits have been suggested as significant markers of adaptation to drought in bread wheat (Triticum aestivum L.). This study was aimed at the identification of a relationship between dehydroascorbate reductase (DHAR, EC 1.8.5.1) and catalase (CAT, EC 1.11.1.6) activities in leaves of wheat plants and stability of yield components under water deficit. The single chromosome substitution lines of cv. Chinese Spring carrying separate chromosomes from the donor Synthetic 6x, an artificial hexaploid combining the genomes of the two wild species, Triticum dicoccoides (AABB) and Aegilops tauschii (DD), were the objects of the investigations. The activities of the DHAR and CAT were correlated with flag leaf relative water content and two indexes of stability of grain yield components under drought across the set substitution lines. The lines carrying a synthetic hexaploid homologous pair of chromosomes 1B, 1D, 2D, 3D or 4D all expressed a low constitutive level of DHAR and the lines carrying chromosomes 3B, 1D, 2D and 3D a low constitutive level of CAT. All were able to increase this level (by fourfold for DHAR and by 1.5-fold for CAT) in response to stress caused by water deficit. When challenged by drought stress, these lines tended to be the most effective in retaining the water status of the leaves and preventing the grain yield components from being compromised. The discovered genetic variability for enzymes activity in leaves of wheat might be a useful selection criterion for drought tolerance.     

Conditional and unconditional QTL mapping of drought-tolerance-related traits of wheat seedling using two related RIL populations

For discovering the quantitative trait loci (QTLs) contributing to early seedling growth and drought tolerance during germination, conditional and unconditional analyses of 12 traits of wheat seedlings: coleoptile length, seedling height, longest root length, root number, seedling fresh weight, stem and leaves fresh weight, root fresh weight, seedling dry weight, stem and leaves dry weight, root dry weight, root to shoot fresh weight ratio, root-to-shoot dry weight ratio, were conducted under two water conditions using two F_8:9 recombinant inbred line (RIL) populations. The results of unconditional analysis are as follows: 88 QTLs accounting for 3.33–77.01% of the phenotypic variations were detected on chromosomes 1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 4A, 4B, 4D, 5A, 5B, 5D, 6A, 6B, 6D, 7A, 7B and 7D. Among these QTLs, 19 were main-effect QTLs with a contribution rate greater than 10%. The results of the conditional QTL analysis of 12 traits under osmotic stress on normal water conditions were as follows: altogether 22 QTLs concerned with drought tolerance were detected on chromosomes 1B, 2A, 2B, 3B, 4A, 5D, 6A, 6D, 7B, and 7D. Of these QTLs, six were main-effect QTLs. These 22 QTLs were all special loci directly concerned with drought tolerance and most of them could not be detected by unconditional analysis. The finding of these QTLs has an important significance for fine-mapping technique, map-based cloning, and molecular marker-assisted selection of early seedling traits, such as growth and drought tolerance.     

小麦叶片水分利用效率及相关生理性状基因的染色体定位

利用中国春-埃及红代换系对控制小麦水分利用效率、光合速率、蒸腾速率、POD活性以及SOD活性等的基因进行了染色体定位。结果表明,控制高水分利用效率的基因可能位于5A和5D染色体上;控制高光效的基因可能位于3A和3D染色体上;控制高蒸腾速率的基因可能位于7B染色体上;诱导POD和SOD活性增强的有利培因可能分别位于7D和6D、2B染色体上。这些研究结果可以为小麦机抗旱节水的遗传育种研究提供一定参号信息。     

Nucleolus organizer competition in Triticum aestivum — Aegilops umbellulata chromosome addition lines

Summary The nucleolar organizer activity of wheat (Triticum aestivum, AABBDD) and Aegilops umbellulata (UU) chromosomes have been analyzed in the complete set of the chromosome addition lines by using a highly reproducible silver-staining procedure. Chromosomes 1U and 5U produce the partial inactivation of wheat nucleolar organizer chromosomes 6B, 1B and 5D. The chromosomes D and G from Ae. umbellulata, which are not SAT-chromosomes, seem to specifically influence the activity of wheat NORs. The predominant status of the U genome with respect to nucleolar competition in the Triticeae is confirmed.     

Back-cross reciprocal monosomic analysis of Fusarium head blight resistance in wheat (Triticum aestivum L.)

 Fusarium head blight (FHB or scab) caused by Fusarium spp. is a widespread disease of cereals causing yield and quality losses and contaminating cereal products with mycotoxins. The breeding of resistant varieties is the method of choice for controlling the disease. Unfortunately, the genetic basis of scab resistance is still poorly understood. We present the results of a back-cross reciprocal monosomic analysis of FHB resistance using the highly resistant Hungarian winter wheat line ‘U-136.1’ and the highly susceptible cultivar ‘Hobbit-sib’. Resistance testing was performed in a field trial artificially inoculated with a Fusarium culmorum conidial suspension. Five hemizygous families containing ‘U-136.1’ chromosomes 6B, 5A, 6D, 1B, and 4B had a visually reduced spread of infection compared to lines having the ‘Hobbit-sib’ chromosome. Chromosome 2B from ‘U-136.1’ had an increased spread of infection. The critical chromosomes controlling seed weight were 6D, 3B, 5A, and 6B while those controlling deoxynivalenol (DON) content were homoeologous groups 2 and 6, although the latter effects were not significant due to a high coefficient of variation. Results from this and other studies show that chromosomes 6D, 6B, 5A, 4D, and 7A have frequently been associated with scab resistance in a number of wheat cultivars. Research groups now attempting to map scab resistance in wheat using markers should pay special attention to the above-mentioned chromosomes. Received: 31 March 1998 / Accepted: 14 July 1998     

Regulation of cholesterol biosynthesis and metabolism in Hep G2 cells by Δ8(14)-15-ketoergostane derivatives

The comparative study of effects of 5α-cholest-8(14)-en-15-on-3β-ol (I), (22E)-5α-ergosta-8(14),22-dien-15-on-3β-ol (II), (22S,23S)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (III), and (22R,23R)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (IV) on HMG-CoA reductase, CYP27A1 and CYP3A4 genes expression in Hep G2 cells was performed. In the contrast to the 15-ketocholestane derivative (I), 15-ketoergostane derivatives (II–IV) decreased the HMG-CoA reductase mRNA level; (22R, 23R)-22,23-oxido-5α-ergost-8(14)-en-15-on-3β-ol (IV) significantly increased CYP3A4 mRNA level (320% from control). Ketosterol (II) was found to be a more potent inhibitor of cholesterol biosynthesis in Hep G2 cells during prolonged incubation, compared with ketosterol (I). The side chain conformation of compounds (I)–(IV) was evaluated by computational modeling; the correlation between biological activity of these compounds and conformational flexibility of their side chains was found. The results obtained indicate that Δ8(14)-15-ketoergostane derivatives may be used as a sterol biosynthesis and metabolism regulators in liver cells.     

Effect of triterpenoid glycosides on α- and β-amylase activity and total protein content in wheat seedlings

Influence of the aleanolic acid glycosides from Silphium perfoliatum L. (silphioside B, C, E and G) and their progenins on the amylase activity and total protein content in wheat seedlings was studied. Treatment of the Triticum aestivum L. seeds with 1–10 μM water solutions of mono- and diglycosides (mono- and bisdesmosines) elevated the α-amylase and total amylase activities in seedlings. Silphioside E containing three glucose moieties in its molecule did not change α-amylase activity, but it did if bis-triglycoside acetylated carbohydrate (as in silphioside C). Effects of 5–10 μM solutions of the active glycosides was comparable with that of exogenous gibberellin A₃ and 6-benzylaminopurine.     

Antifouling Activity of Bromotyrosine-Derived Sponge Metabolites and Synthetic Analogues

Eighteen brominated sponge-derived metabolites and synthetic analogues were analyzed for antilarval settlement of Balanus improvisus. Only compounds exhibiting oxime substituents including bastadin-3 (4), −4 (1), −9 (2), and −16 (3), hemibastadin-1 (6), aplysamine-2 (5), and psammaplin A (10) turned out to inhibit larval settling at 1 to 10 μM. Analogues of hemibastadin-1 (6) were synthesized and tested for structure activity studies. Debromohemibastadin-1 (8) inhibited settling of B. improvisus, albeit at lower concentrations than hemibastadin-1 (6). Both 6 and 8 also induced cyprid mortality. 5,5′-dibromohemibastadin-1 (7) proved to be nontoxic, but settlement inhibition was observed at 10 μM. Tyrosinyltyramine (9), lacking the oxime function, was not antifouling active and was non-toxic at 100 μM. Hemibastadin-1 (6) and the synthetic products showed no general toxicity when tested against brine shrimp larvae. In contrast to the lipophilic psammaplin A (10), the hydrophilic sulfated psammaplin A derivative (11) showed no antifouling activity even though it contains an oxime group. We therefore hypothesize that the compound needs to cross membranes (probably by diffusion) and that the target for psammaplin A lies intracellularly.     

Isolation and Structural Determination of Makinolide B from Streptomyces sp. MK-19

A new 16-membered macrolide named makinolide B (1) was isolated from Streptomyces sp. MK-19. The structure of makinolide B (1) was determined on the basis of 2D NMR experiments involving DQF-COSY, TOCSY, HSQC, and HMBC methods. Application of the paper disk diffusion method to makinolide B (1) showed weak antibacterial activity against Staphylococcus aureus at the dose of 100 µg/disk.     

Hybrid flavan-chalcones, aromatase and lipoxygenase inhibitors, from Desmos cochinchinensis

Hybrid flavan-chalcones, desmosflavans A (1) and B (2), together with three known compounds, cardamonin (3), pinocembrin (4) and chrysin (5), were isolated from leaves of Desmos cochinchinensis. Cardamonin (3) and chrysin (5) exhibited potent antioxidant activity with 15.0 and 12.2 ORAC units. Desmosflavans A (1) and B (2), pinocembrin (4), and chrysin (5) were found to be inhibitors of aromatase with respective IC₅₀ values of 1.8, 3.3, 0.9, and 0.8 μM. Desmosflavan A (1) inhibited lipoxygenase with the IC₅₀ value of 4.4 μM. Desmosflavan A (1) exhibited cytotoxic activity with IC₅₀ values of 0.29–3.75 μg/mL, while desmosflavan B (2) showed IC₅₀ values of 1.71–27.0 μg/mL.     

Regulation of nebramycin biosynthesis by inorganic phosphate

The effect of inorganic phosphate on the biosynthesis of nebramycin factors2, 4 and5′ was studied inStreptomyces tenebrarius strain A (forming2, 4 and5′ in natural ratios) and its mutants B (forming predominantly2), C (forming2 as the only major product) and D (forming predominantly5′). In phosphate-supplemented complex media, the production of2 in A, B and C was reduced by 20–70%, while the yields of5′ remained unchanged in A and decreased by 30–60% in B. The production of4 increased by 50–90% in A and was fully suppressed in B. In D the biosynthesis of the three factors was inhibited completely.     

QTL mapping for germination of seeds obtained from previous wheat generation under drought

The QTLs controlling germination and early seedling growth were mapped using seeds acquired from mapping population and parental lines of Chinese Spring and SQ1 grown under water-limited conditions, severe drought (SDr) and well-watered plants (C). Germination ability was determined by performing a standard germination test based on the quantification of the germination percentage (GP24) of seeds incubated for 24 h at 25°C in the dark. Early seedling growth was evaluated on the basis of the length of the root and leaf at the 6th day of the experiment. QTLs were identified by composite interval mapping method using Windows QTLCartographer 2.5 software. For the traits studied, a total of thirty eight additive QTLs were identified. Seventeen QTLs were mapped in C on chromosomes: 1A, 2A, 7A, 1B, 2B, 3B, 4B, 5B, 6B, 7B, 2D, 3D, 4D and 6D, while twenty one QTLs were identified in SDr on chromosomes: 1A, 2A, 5A, 2B, 3B, 4B, 5B, 6B, 7B, 3D, 5D and 6D. Most of the QTLs for GP and early leaf growth parameters were clustered on chromosome 4B (associated with the Rht-B1 marker) both in C and SDr plants. The results indicate the complex and polygenic nature of germination.     

Physical mapping and molecular-cytogenetic analysis of substitutions and translocations involving chromosome 1D in synthetic hexaploid triticale

 Chromosome 1D, which carries the advantageous alleles of glutenin and gliadin, attracts major interest with respect to improving the bread-making quality of triticale. Eighty-one BC₁F₄ lines from different primary and secondary hexaploid triticale crosses were selected for 1D chromatin analysis using SDS-PAGE and C-banding. In situ hybridization and RFLP-based comparative physical mapping of group 1 chromosomes revealed 20 lines with complete 1D (1A) substitutions. Nine 1D (1B) substitutions, six 1D (1R) substitutions and one 1D addition line were also selected. Three lines were pure AABBRR hexaploids without any D-genome chromosomes. For the remaining 42 lines (51.8%), a wide spectrum of 20 different recombinations between chromosomes 1A and 1D was uncovered. Altogether, they were generated without any earlier irradiation, tissue culture or genetic induction of chromosome pairing. In addition, 14 translocations between 1B/1D, 1A/1R, 1B/1R, 1D/1R and 1A/1B were detected. Considerable variability for sedimentation values was found, with the highest sedimentation values among lines with complete 1D chromosomes. The implications of using triticale as a model for generating compensating chromosome rearrangements in defined homoeologous groups and the breeding potential of D-genome chromatin introgressed into triticale with improved sedimentation values are discussed. Received: 27 July 1998 / Accepted: 5 August 1998     

12057单体系及其二体抗旱生理指标的比较

利用１２０５７单体及其二体连续两年进行抗旱生理招标的比较,结果表明：１２０５７单体系珉春二体在灌浆中期旗叶相对含水量、细胞膜稳定性、叶片渗透势以及渗透调节能力等均存在差异。其中２Ｂ、３Ｂ、６Ｂ单体相对含水量较高;５Ａ单体叶组织膜稳定性较高;４Ｂ、５Ｂ、４Ｄ、６Ｂ、３Ａ单体的渗透势较低;６Ｂ、４Ｂ、３Ｂ、４Ｄ、、Ｂ单体的渗透调节能力较高。此外看出部分同源染色体群对上述生理招标的反应具有相似性。     

Antitranspirant functions of stem periderms and their influence on corticular photosynthesis under drought stress

Transpiration and photosynthesis of current-year stems and adult leaves of different deciduous tree species were investigated to estimate their probable influence on carbon balance. Peridermal transpiration of young stems was found to be rather small as compared to the transpiration of leaves (stem/leaf like 1/5–1/20). A characteristic that was mainly attributable to the lower peridermal conductance to water and CO₂, which made up only 8–28% of stomatal conductance. Water vapour conductance was significantly lower in stems, but also non-responsive to PAR, which led to a comparatively higher water use efficiency (WUE, ratio assimilation/transpiration). Thus, although corticular photosynthesis reached only 11–37% of leaf photosynthesis, it may be a means of improving the carbon balance of stems under limited water availability. The influence of drought stress on primary photosynthetic reactions was also studied. Under simulated drought conditions the drying time needed to provoke a 50% reduction (t ₅₀) in dark- and light-adapted PSII efficiency (Fv/Fm, ΔF/Fm′) was up to ten times higher in stems than in leaves. Nevertheless, up to a relative water deficit (RWD) of around 40–50% dark-adapted PSII efficiency of leaves and stems was rather insensitive to dehydration, showing that the efficiency of open PS II reaction centres is not impaired. Thus, it may be concluded that in stems as well as in leaves the primary site of drought damage is at the level of dark enzyme reactions and not within PSII. However, enduring severe drought caused photoinhibitory damage to the photosynthetic apparatus of leaves and stems; thereby RWD₅₀ values (= RWD needed to provoke a 50% reduction in Fv/Fm ad ΔF/Fm′) were comparably lower in stems as compared to leaves, indicating a possibly higher drought sensitivity of the cortex chlorenchyma.     

Identification of genetic factors controlling kernel hardness and related traits in a recombinant inbred population derived from a soft × ‘extra-soft’ wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cross

Kernel hardness or texture, used to classify wheat (Triticum aestivum L.) into soft and hard classes, is a major determinant of milling and baking quality. Wheat genotypes in the soft class that are termed ‘extra-soft’ (with kernel hardness in the lower end of the spectrum) have been associated with superior end-use quality. In order to better understand the relationship between kernel hardness, milling yield, and various agronomic traits, we performed quantitative trait mapping using a recombinant inbred line population derived from a cross between a common soft wheat line and a genotype classified as an ‘extra-soft’ line. A total of 47 significant quantitative trait loci (QTL) (LOD ≥ 3.0) were identified for nine traits with the number of QTL affecting each trait ranging from three to nine. The percentage of phenotypic variance explained by these QTL ranged from 3.7 to 50.3%. Six QTL associated with kernel hardness and break flour yield were detected on chromosomes 1BS, 4BS, 5BS, 2DS, 4DS, and 5DL. The two most important QTL were mapped onto orthologous regions on chromosomes 4DS (Xbarc1118–Rht-D1) and 4BS (Xwmc617–Rht-B1). These results indicated that the ‘extra-soft’ characteristic was not controlled by the Hardness (Ha) locus on chromosome 5DS. QTL for eight agronomic traits occupied two genomic regions near semi-dwarf genes Rht-D1 on chromosome 4DS and Rht-B1 on chromosome 4BS. The clustering of these QTL is either due to the pleiotropic effects of single genes or tight linkage of genes controlling these various traits.     

干旱-复水对两种石斛属植物叶水势的影响

石斛属植物多附着在其他植物体或岩石上,水分获取困难,其特殊的水分利用策略是其生存和发展的重要保证.为弄清石斛属植物对干旱胁迫的适应能力和机制,该文选用3年生金钗石斛和铁皮石斛,通过盆栽控水进行干旱胁迫和复水处理,探讨在不同干旱历时和干旱后复水条件下两种石斛的叶水势变化情况.结果表明:随着干旱时间的延长,两种石斛叶水势均...     

Pitipeptolides C-F, antimycobacterial cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula from Guam

Pitipeptolides A (1) and B (2) are cyclic depsipeptides isolated from the marine cyanobacterium Lyngbya majuscula from Piti Bomb Holes, Guam. Additional analogues have now been isolated by revisiting larger collections of the same cyanobacterium. The four identified analogues, pitipeptolides C–F (3–6), are the tetrahydro analogue (3), an analogue with a lower degree of methylation (4) as well as two homologues (5 and 6) of pitipeptolide A. Their structures were elucidated using 2D NMR experiments, chiral HPLC analysis and comparison with pitipeptolide A. The identified analogues showed weaker cytotoxic activities compared to the two major parent compounds, pitipeptolides A (1) and B (2), against HT-29 colon adenocarcinoma and MCF7 breast cancer cells. On the other hand, pitipeptolide F (6) was the most potent pitipeptolide in a disc diffusion assay against Mycobacterium tuberculosis. The latter finding suggests that the structure of pitipeptolides could be optimized for selective antibacterial activity.