Metabolism of [3H]gibberellin A4 in somatic suspension cell cultures of carrot

The native gibberellin A₄ (GA₄), in radioactive form ([1,2-³H]GA₄, 1.06 Ci/mmol), was fed to carrot somatic cell cultures (suspension and immobilized cell systems) and its metabolism over a 48 hr period was investigated. It was found that the [³H]GA₄ was metabolized to at least two GAs, [³H]GA₁ and [³H]GA₈, six GA glucosyl conjugates, [³H]GA₁-0(3)-glucoside, [³H]GA₁-0(13)-glucoside, [³H]GA₁-glucosyl ester, [³H]GA₄-glucoside, [³H]GA₄-glucosyl ester, a [³H]GA₈ glucosyl conjugate(s) and a previously unknown [³H]GA₁ glucosyl conjugate ([³H]GA₁-0(3,13)-diglucoside-like compound). The GA₁-diglucoside-like compound was found only in extracts of cells and was present in significant amounts (33 % of total extractable radioactivity). All other metabolites were present in both cells and medium. For extracts of the medium, no differences between the suspension and immobilized cultures existed in types of [³H]GA₄ metabolites although quantitative differences were apparent.     

Effect of pollination and fertilization on the expression of genes related to floral transition, hormone synthesis and berry development in grapevine

In the present work, the effect of assisted fertilization on anatomical, morphological and gene expression changes occurring in carpels and during early stages of berry development in Vitis vinifera were studied. Inflorescences were emasculated before capfall, immediately manually pollinated (EP) and fruit development was compared to emasculated but non-pollinated (ENP) and self-pollinated inflorescences (NESP). The diameter of berries derived from pollinated flowers (EP and NESP) was significantly higher than from non-pollinated flowers (ENP) at 21 days after emasculation/pollination (DAE), and a rapid increase in the size of the inner mesocarp, together with the presence of an embryo-like structure, were observed. The expression of gibberellin oxidases (GA20ox and GA2ox), anthranilate synthase (related to auxin synthesis) and cytokinin synthase coding genes was studied to assess the relationship between hormone synthesis and early berry development, while flower patterning genes were analyzed to describe floral transition. Significant expression changes were found for hormone-related genes, suggesting that their expression at early stages of berry development (13 DAE) is related to cell division and differentiation of mesocarp tissue at a later stage (21 DAE). Expression of hormone-related genes also correlates with the expression of VvHB13, a gene related to mesocarp expansion, and with an increased repression of floral patterning genes (PISTILLATA and TM6), which may contribute to prevent floral transition inhibiting fruit growth before fertilization takes place.     

The role of the glutathione system during dehydration of Boea hygroscopica

Plants of Boea hygroscopica F. Muell were subjected to dehydration for 25 days until the relative water content was 23%. The rate of water loss was very slow during the first 12 days of dehydration while it dramatically increased during the last 3 days of the treatment. On day 12 of dehydration total glutathione content was reduced to 24% of the control level and was mainly present in the oxidized form. At that time an oxidation of the sulfhydryl groups of soluble proteins was observed. A protection of glutathione against oxidation of the sulfhydryl groups of soluble proteins was established only after 22 days of desiccation, at the same time as glutathione began to accumulate. During the whole desiccation period enzyme activities related to glutathione utilization and regeneration and the activity of NADP⁺-dependent glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), which contains essential sulfhydryl groups, were maintained. The results of the present experiment suggest that during dehydration of Boea hygroscopica glutathione has above all, a primary role in the protection of the sulfhydryl groups of the thylakoid proteins, which were maintained in the reduced form during the whole dehydration period.     

识别未衍生化的13—羟化GAs及其葡萄糖苷的单克隆抗体

抗ＧＡ３ 及其葡萄糖苷的ＭＡＢ１０单克隆抗体源于以ＧＡ３ 中的３ 位羟基（３－ＯＨ）为偶联位点,人血清白蛋白（ＨＳＡ）为载体合成的ＧＡ３－３－ＨＳＡ 免疫原． 该抗体对１３－羟化ＧＡｓ（１３－ＯＨＧＡｓ、ＧＡ１、ＧＡ３、ＧＡ５ 等）和ＧＡ３ 葡萄糖苷具有高亲和力． ７ 位羧基的甲酯化可显著降低ＭＡＢ１０ 对１３－ＯＨ ＧＡｓ的亲和力,而３－ＯＨ 的糖苷化却未降低其亲和力． 用该抗体建立的两种分别用于ＧＡ３ 及其葡萄糖苷测定的酶联免疫吸附法（ＥＬＩＳＡ）,其检测线性范围均为０．２～２０ ｐｍ ｏｌ． 借助这两种ＥＬＩＳＡｓ,研究了羊蹄（Ｒｕｍ ｅｘ ｊａｐｏｎｉｃｕｓ）叶片中ＧＡ３ 及其类似ＧＡｓ和葡萄糖苷的动态变化．结果表明,叶片衰老与游离态ＧＡｓ的糖苷化有关;而６－ＢＡ 延缓衰老则可能与其减缓ＧＡｓ的糖苷化有关     

Changes in carbohydrate contents of <Emphasis Type="Italic">Zantedeschia</Emphasis> leaves under gibberellin-stimulated flowering

The effect of gibberellic acid (GA₃) on the carbohydrate accumulation in relation to vegetative growth of Zantedeschia ‘Black Magic’ plants undergoing transition to flowering was investigated. In response to GA treatment the carbohydrate level increased independently of earlier stimulation of shoot emergence. Under vegetative growth stage the content of reducing sugars of leaf blades was 2.5-fold higher than in control plants, and suggests the stimulation of photosynthetic activity. The changes observed during the flowering, in principle noted in petiole tissues, support the GA-effect on assimilate transport to the sink organs. Moreover, the high level of non-structural carbohydrates in petiole tissues, in particular reducing sugars, can be an effect of photosynthetic activity of these organs and/or essential for osmoregulation and high turgor pressure. The results indicate that apart from the influence on the shoot emergence, the GAs may stimulate the photosynthetic activity from the beginning of shoot growth and are thus responsible for the enhancement of callas flower yield.     

赤霉素对拟南芥主根分生区和伸长区的调控

赤霉素是一类重要的植物激素,在植物整个生长发育的调控过程中起重要作用。近年来,人们发现赤霉素对拟南芥主根生长存在促进作用。本文从根系的解剖结构、赤霉素的源靶部位、促进作用的机理、赤霉素信号转导途径以及与其他激素的关系等方面,综述了赤霉素对拟南芥主根分生区和伸长区的影响。     

Hydrolysis of [17,17-2H2]gibberellin A20-glucoside and [17,17-2H2]gibberellin A20-glucosyl ester by Azospirillum lipoferum cultured in a nitrogen-free biotin-Based chemically-defined medium

Azospirillum lipoferum strain USA 5b, a gibberellin producing bacterium, was cultured in a nitrogen-free biotin-based chemically-defined medium in the presence of the glucosyl ester or the 13-O-glucoside of [17,17-²H₂]-gibberellin A₂₀. The [17,17-²H₂]-gibberellin A₂₀ conjugates were added at both the stationary phase of the cultures and at the beginning of the growth curve. Metabolism of the conjugates was examined after 72 h of incubation using capillary gas chromatography-mass spectrometry, with identification by full scan mass spectra. Metabolites identified were [17,17-²H₂]-gibberellin A₂₀, [17,17-²H₂]-gibberellin A₁ and [17,17-²H₂]-gibberellin A₃. Also, in the Azospirillum cultures fed at the beginning of the growth curve, gibberellin A₅ and gibberellin A₂₀ were characterized as endogenous by mass spectrometry/full spectrum. These results support the concept that the growth promotion in plants that is induced by Azospirillum infection may occur by a combination of both gibberellin production and gibberellin-glucoside/glucosyl ester deconjugation by the bacterium.     

Thermoperiodic control of stem elongation and endogenous gibberellins in Campanula isophylla

The effect of day/night temperature regimes on stem elongation and on the content of endogenous gibberellins (GAs) in vegetatively propagated plants of Campanula isophylla cv. Hvit have been studied. Compared with a constant temperature regime at 18°C (18/18°C), stem and internode elongation was enhanced significantly by a combination of high day/low night temperature (21/15°C) and inhibited by an opposite regime (15/21°C). Gibberellins A₁, A₁₉, A₄₄, A₅₃, and A₉₇ were identified as endogenous components in Campanula. (GA₉₇ was earlier referred to as 2-OH-GA₅₃.) Quantitative analysis of the endogenous GAs indicates that temperature regimes that stimulate elongation growth are accompanied by an increase in the level of GA₁, GA₁₉, and GA₄₄. On the other hand, in plants grown under conditions that reduced stem elongation growth, there was an increased level of GA₉₇.Abbreviations DIF difference between day temperature and night temperature - GA gibberellin - HPLC high performance liquid chromatography - GC-MS gas chromatography-mass chromatography - SPE solid phase extraction - TMS trimethylsilyl - MSTFA N-methyl-N-TMS-trifluoroacetamide - KRI Kovats retention index - SIM selected ion monitoring - D2 deuterated     

异戊二烯类植物激素赤霉素和脱落酸的代谢调控

赤霉素和脱落酸在植物生理过程中具有重要的调控作用,其生物合成途径迄今已基本阐明。赤霉素与类胡萝卜素的生物合成途径具有共同前体牻牛儿基牻牛儿基二磷酸,而脱落酸则直接来自于类胡萝卜素。参与这两种植物激素和类胡萝卜素代谢过程的大多数酶基因已经从不同植物中获得克隆;各种调控方式也随着分子生物学的研究工作而得到鉴定。本文就近年来对赤霉素和脱落酸等代谢调控机制及其与植物类胡萝卜素代谢之间关系的研究工作做简要回顾。