激素信号调节果树花芽发端假说的概述

概述了Lavee和Bangerth两个激素信号调节花芽发端假说的内容和证据,并分析了这两个假说的优缺点。认为旺盛营养生长的梢尖或正在发育果实的种子产生的极性运输的生长素（IAA）可能是抑制果树花芽发端的信号。尚不能确定来自正在发育果实种子的赤霉素（GA）自身是抑制花芽发端的信号,还是参与调节花芽发端信号的产生。营养芽中高水平的细胞分裂素（CTK）促进花芽发端,可能与较弱的IAA信号有关。同时指出,激素信号调节花芽发端的机理还有待完善。     

果树花芽孕育的研究概况

果树花芽孕育是一个成花因素积累的过程 ,也是芽顶端花原基形成前所必要的活动。随着研究手段的改进和水平的提高 ,近年来人们逐渐弄清了果树花芽孕育的概念、花芽孕育期间的重要生理生化变化以及外界因素调控花芽孕育的可能方式 ,而对果树花芽孕育调控基因的研究处于起步阶段。     

果树花芽孕育的研究概况

果树花芽孕育是一个成花因素积累的过程,也是芽顶端花原基形成前所必要的活动。随着研究手段的改进和水平的提高,近年来人们逐渐弄清了果树花芽孕育的概念、花芽孕育期间的重要生理生化变化以及外界因素调控花芽孕育的可能方式,而对果树花芽孕育调控基因的研究处于起步阶段。     

大岩桐花瓣切块离体培养高频率花芽再生

该文报道了大岩桐花瓣切块离体培养再生花现象,花瓣切块再生花有两种方式：一种是仅再生花芽（命名为BF）;另一种是既再生花芽也再生营养芽（命名为BF＋V）。花芽再生的能力与光照、花芽大小及培养基中赤霉素和细胞分裂素浓度紧密相关。当培养基中含有1.0 mg/L GA3时,BA的添加会显著增加总花芽（BF＋BF＋V）的形成率,添加0.5 mg/L BA时,总花芽形成率达100%。在暗中培养时,BF达93.4%。不同大小花芽的花瓣再生花的能力不同,7 mm直径花芽的BF最高,达86.7%。同时,对花芽再生过程中花瓣切块的组织结构形态变化也进行了观察。     

牡丹冬季室内催花过程中内源激素含量的变化

牡丹品种朱砂垒(PaeoniasuffruticosaAndr.cv.Zhushalei)在冬季室内催花过程中7种内源激素含量变化不同。玉米素核苷(Z ZR)、生长素(IAA)和赤霉素(GA3)的含量在花生长发育过程中处于较高水平;而脱落酸(ABA)、异戊烯基腺苷(IP IPA)、二氢玉米素核苷(DHZ DHZR)、赤霉素(GA4)的含量低于上述3种内源激素。激素平衡方面,GAs/ABA、CTKs/ABA、IAA/ABA处于较高水平,变化幅度较大。在催花过程中,内源激素以及其平衡影响牡丹花的生长发育。本研究结果对牡丹花期调控提供理论依据。     

外源激素对诱导风信子同一花被外植体不同部位细胞分化花芽的影响

本文研究了不同外源激素组合对诱导同一花被不同部位细胞分化花芽的影响,测定了花被上部、中部、下部切块离体培养前后的内部ＩＡＡ和Ｚ＋ＺＲ含量。结果表明,风信子同一花被不同部位细胞均能分化花芽,当ＭＳ培养基中附加２．０ｍｇ／Ｌ的ｚｅａｔｉｎ或６－ＢＡＰ时,随着外源ＩＡＡ浓度从０升高到１０．０ｍｇ／Ｌ,花芽分化部位由花被下部向上部移动。     

外源激素对风信子再生花芽发育的控制

外源激素在诱导再生花芽花器官发生和控制它们的数目中的关键作用被进一步证实。首先通过２ｍｇ／Ｌ ６－ＢＡ和０．１ｍｇ／Ｌ ２,４－Ｄ的激素组合诱导风信子Ｈｙａｃｉｎｔｈｕｓ ｏｒｉｅｎｔａｌｉｓ Ｌ．ｃｖ．Ｗｈｉｔｅ ｐｅａｒｌ）花芽从花被外植体发生,然后保持这种激素浓度,成功地控制了１００多片花被片的连续发生（自然情况下一个风信子花芽仅有６片花被片）。改变激素浓度（２ｍｇ／Ｌ ６－ＢＡ和０～０．０     

生长素和细胞分裂素在调节豌豆根系缺铁反应中的作用

在水培条件下研究了生长素和细胞分裂素对两种基因型豌豆根系铁还原力的影响。结果表明,去顶,顶端涂抹ＮＡＡ和茎基部涂抹ＣＭＥ都不影响豌豆根系铁还原力。茎尖,茎基部和根系的ＩＡＡ、Ｚ／ＺＲ含量与根系铁还原力之间没有明显的相关性。     

丛枝菌根真菌对玉米和棉花内源激素的影响*

在温室盆栽条件下研究了丛枝菌根（Ａｒｂｕｓｃｕｌａｒ　ｍｙｃｏｒｒｈｉｚａｓ,ＡＭ）真菌：ＧｉｇａｓｐｏｒａｒｏｓｅａＮｉｃｏｌ．＆Ｓｃｈｅｎｃｋ、Ｇｌｏｍｕｓ　ｍｏｓｓｅａｅ（Ｎｉｃｏｌ．＆　Ｇｅｒｄ．）Ｇｅｒｄｅｍａｎｎ　＆Ｔｒａｐｐｅ和Ｇｌｏｍｕｓ　ｖｅｒｓｉｆｏｒｍｅ　（Ｋａｒｓｔｅｎ）Ｂｅｒｅｈ对玉米和棉花植株内源激素的影响。结果表明,ＡＭ真菌在正常供水和干旱条件下均能显著提高玉米和棉花植株叶片和根内玉米素、生长素和赤霉素的含量,并降低脱落酸的含量。在植物体内含磷量、生长量及其生长发育阶段等一致、仅存在接种与不接种唯一差异条件下,供试ＡＭ真菌同样能改变玉米和棉花植株内源激素的平衡状况。接种处理植株的脱落酸含量与气孔阻力呈正相关关系。表明玉米和棉花植株抗旱性和生长状况的改善与ＡＭ真菌改变内源激素的平衡状况有关。接种ＡＭ真菌的植株表现较强的抗旱性;其生长量也显著大于不接种的对照。ＧＩ．ｖｅｒｓｉｆｏｒｍｅ的效应最大。     

Hormonal Regulation of Tomato Fruit Development: A Molecular Perspective

Fruit development is a complex yet tightly regulated process. The developing fruit undergoes phases of cell division and expansion followed by numerous metabolic changes leading to ripening. Plant hormones are known to affect many aspects of fruit growth and development. In addition to the five classic hormones (auxins, gibberellins, cytokinins, abscisic acid and ethylene) a few other growth regulators that play roles in fruit development are now gaining recognition. Exogenous application of various hormones to different stages of developing fruits and endogenous quantifications have highlighted their importance during fruit development. Information acquired through biochemical, genetic and molecular studies is now beginning to reveal the possible mode of hormonal regulation of fruit development at molecular levels. In the present article, we have reviewed studies revealing hormonal control of fruit development using tomato as a model system with emphasis on molecular genetics.     

One for All and All for One: Cross-Talk of Multiple Signals Controlling the Plant Phenotype

The plant hormone ethylene plays a pivotal role in steering various processes by regulating the biosynthesis, distribution, or signal transduction of other hormones. Ethylene also mediates the effects of other hormones. Similarly, hormones control the ethylene synthesis and signalling pathway. Eventually, integration of this network of signals leads to an appropriate morphological or biochemical response. Consequently, this cross-talk results in the characteristic plasticity associated with plant development. Here, the interplay of ethylene with other hormones is described for germination and seedling growth, stomatal control, and tissue elongation. The mechanisms by which this occurs are discussed in more detail.     

Hormone Profiling by LC-QToF-MS/MS in Dormant <Emphasis Type="Italic">Macadamia integrifolia</Emphasis>: Correlations with Abnormal Vertical Growth

A method for analyzing multiple plant hormone groups in small samples with a complex matrix was developed to initiate a study of the physiology of abnormal vertical growth (AVG) in Macadamia integrifolia (cv. HAES344). Cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), and auxins were detected in xylem sap and apical and lateral buds using high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QToF-MS/MS). The extraction method separated compounds with high sensitivity in positive (CKs) and negative (ABA, auxins, GAs) modes of QToF-MS/MS. CK profiles differed in xylem sap and apical and lateral buds irrespective of AVG symptoms. Trans-zeatin riboside (t-ZR) was dominant in sap of normal and AVG trees (∼4 and 6 pmol g⁻¹ FW, respectively). In apical buds isopentenyl adenine (iP) (∼30 pmol g⁻¹ FW) was the most abundant CK, and in lateral buds trans-zeatin (t-Z) (22–24 pmol g⁻¹ FW) and iP (24–30 pmol g⁻¹ FW) were the most abundant. t-Z levels of AVG trees were higher in apical buds (13.88 vs. 6.6 pmol g⁻¹ FW, p < 0.05) and lower in sap (0.16 vs. 0.51 pmol ml⁻¹, p < 0.005) compared to normal trees. ABA in lateral buds was 1.9 times higher (p < 0.001) in AVG. IAA was below quantification, whereas indole-3-butyric acid (IBA) was consistently present. GA₇ was the dominant GA in apical and lateral buds of all trees (100–150 pmol g⁻¹ FW). GA_{3, 4, & 9} were consistently present at low concentrations (<12 pmol g⁻¹ FW) in buds. GAs_{1, 3, & 9} were detected in xylem sap at low concentrations (<0.5 pmol g⁻¹ FW). Differences in sap amino acids (AA) were also assessed. In sap from AVG trees, asparagine and glutamine increased significantly (p < 0.05) in their contribution to total AA. Potential AVG hormone correlations are discussed.     

Parasitism of seed of Douglas fir (<Emphasis Type="Italic">Pseudotsuga menziesii</Emphasis>) by the seed chalcid, <Emphasis Type="Italic">Megastigmus spermotrophus</Emphasis>, and its influence on seed hormone physiology

Parasitism of Douglas fir (Pseudotsuga menziesii) megagametophytes by the seed chalcid, Megastigmus spermotrophus Wachtl, occurs naturally after pollination but before fertilization. In the absence of fertilization, the presence of insect larvae within the megagametophyte prevents abortion and the storage tissue continues to develop as if the seed had been fertilized. We investigated the effect of parasitism on the metabolism of abscisic acid (ABA), auxins, cytokinins, and gibberellins during early development of Douglas fir seeds. Hormones and hormone metabolites of infested and uninfested megagametophytes with or without pollination were analyzed by HPLC–ESI/MS/MS. At 1 week after Megastigmus introduction, the insect’s presence stimulated ABA accumulation in unpollinated megagametophytes compared to unpollinated, unparasitized megagametophytes. In pollinated material, parasitism did not stimulate ABA accumulation compared to levels present in unparasitized megagametophytes. In all four treatments, the metabolism of ABA occurred primarily through conjugation to the ABA glucose ester (ABAGE), while the 7′-, 8′- and, 9′-hydroxylation pathways were only minor. ABAGE levels declined with time in all treatments and this occurred to a greater extent in pollinated, parasitized megagametophytes, suggesting that the insect’s presence induced the dramatic decrease in ABAGE. Although there were temporal variations in the auxin, cytokinin, and gibberellin profiles of parasitized megagametophytes, the profiles were generally similar to those of unparasitized megagametophytes. Our results suggest that failure of parasitized megagametophytes to abort may be due to the insect inducing similar hormone profiles to those present during normal development of Douglas fir seed.     

The role of oxidative stress induced by growth regulators in the regeneration process of wheat

As part of work to optimize the regeneration processes of winter wheat callus culture the effects of two auxins (2,4-D, IAA), two cytokinins (kinetin, zeatin), and the fungal mycotoxin zearalenone, were tested individually in vitro using embryo-, and inflorescence-derived callus. To determine the role of oxidative stress in cell regeneration, changes in the basic antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs) were investigated. In general, zearalenone (ZEN) was found to be more effective than cytokinin treatments for inducing shoot production, whereas auxins suppressed the regeneration process. Regenerating callus showed higher induction of these antioxidant enzymes in comparison with non-regenerating callus. SOD, CAT and POD activities were higher in callus derived from inflorescence than in callus derived from immature embryo. Activities of SOD, CAT and POD in culture derived from immature embryos were depending on type of growth regulator in medium. The highest enzyme activities were observed in non-regenerating tissues after auxins treatment and in regenerating tissues after cytokinins treatment. The effect of ZEN was similar to that of cytokinins. One MnSOD band and two Cu/ZnSOD bands were detected in all cultures. Changes in SOD izoform patterns occurred in callus culture on media with auxins and ZEN, but not on media with cytokinins. Our results suggest that callus regeneration is associated with reactive oxygen species production induced by specific growth regulators. Reactive oxygen species under the control of cellular antioxidant machinery can mediate signalling pathways between exogenously applied growth regulators and the induction and/or creation of the direction of morphogenesis.     

Nuclear Localization Signals in p170, the Large Subunit of Translation Initiation Factor 3

Apart from their role in translation, eukaryotic translation factors or their individual subunits may perform other functions, in particular, regulating nuclear processes. Primary structure analysis revealed four potential nuclear localization signals (NLS) in the human eIF3 large subunit, p170. NLS were tested for ability to direct p170 into the nucleus. For this purpose, cDNAs coding for p170 fragments fused with the green fluorescent protein were expressed in CV-1 and Cos-1 cultured monkey cells. The location of the expression product was studied by fluorescence microscopy. At least two of the four putative bipartite NLS proved to direct the corresponding p170 fragments into the nucleus. Larger p170 fragments with the same NLS were retained in the cytoplasm. It was assumed that, with the help of some specific factors or after limited proteolysis, p170 enters the nucleus and participates in regulating genome expression. Alternatively, the cytoplasmic function of p170 might be regulated via a reversible binding of integrins to NLS.     

Molecular Mechanisms of Translation Initiation in Mammals Studied by in vitroReconstruction of Initiation Complexes

Papers on the mechanisms of translation initiation in mammals studied by reconstruction of initiation complexes from individual components are reviewed. The author points to the constraints of this approach and to the pitfalls ignoring which one might come to erroneous conclusions and even artifacts. In addition, some methods employed in the field as well as some technical problems are discussed in the paper, together with the means of obviating them. The review could be a guidebook for newcomers into this quite labor-consuming field.     

逆转录-聚合酶链式反应检测果树RNA病毒

为调查主要果树携带苹果褪绿叶斑病毒(ACLSV)、苹果茎沟病毒(ASGV)、苹果茎痘病毒(ASPV)和李属坏死环斑病毒(PNRSV)的情况,以指示植物为试材,优化了四种病毒的逆转录-聚合酶链式反应(RT-PCR)检测体系.使用该优化体系检测了苹果树、樱桃树、桃树中携带上述四种病毒的情况.结果:建立了特异性强、灵敏度高、成本低的RT-PCR检测体系;同时又证明主要果树被这几种病毒单独感染和复合感染的程度均较高.     

降低mRNA翻译起始区的稳定性原核非融合表达HAb18GEF

为在大肠杆菌中非融合表达肝癌相关抗原HAb18G胞外区片段（HAb18GEF）,将HAb18GEF基因的cDNA插入原核表达载体pET21a+。通过计算机辅助设计,对重组的HAb18GEF/pET21a+的mRNA翻译起始区（TIR）的二级结构和密码子偏性同时进行预测。结果发现其存在稳定的茎环结构和许多稀有密码子。通过优化二级结构和优化密码子偏性二种策略分别来降低HAb18GEF/pET21a+的mRNA翻译起始区（TIR）的稳定性。在不改变氨基酸序列的前提下,利用密码子的简并性,通过非连续定点突变实现这两种优化。将突变前后的重组子经酶切鉴定和测序验证后,转化感受态JM109DE3宿主菌后,随机挑菌37℃下用IPTG诱导表达。SDSPAGE、间接ELISA、Western blot 和细胞分级分离法分析这些重组子的诱导表达情况。RNA dot blot对比分析优化前后目的基因mRNA的量。结果证明,成功地构建了HAb18GEF/pET21a+及其二种优化突变体。仅优化TIR区二级结构或仅优化TIR区密码子偏性均能实现HAb18GEF蛋白的非融合表达,而未优化的重组子不表达任何HAb18GEF。非融合表达产物在大肠杆菌中主要以包涵体形式存在,高达293%。由于过表达和细胞渗漏,培养基和周质腔中也可检测到少许的HAb18GEF。优化二级结构和优化密码子偏性二种策略的HAb18GEF的非融合表达量基本相同。优化前后HAb18GEF转录的mRNA量没有差别。这些结果表明,降低mRNA翻译起始区的稳定性可实现肝癌相关抗原HAb18G胞外区片段在大肠杆菌中的非融合表达。