Elicitor‐induced changes of wall‐bound and secreted peroxidase activities in suspension‐cultured spruce (Picea abies) cells are attenuated by auxins

In ectomycorrhizae auxins are proposed to attenuate elicitor-induced defence reactions in the host plant. To examine this hypothesis we compared the elicitor-induced accumulation of peroxidase isoforms between suspension-cultured spruce (Picea abies[L.] Karst.) cells incubated in media with and without auxins. In spruce cells changes in ionically and covalently wall-bound as well as symplasmic peroxidase (EC 1.11.1.7) activities were observed when elicitors from the following fungal species were applied: (1) Hebeloma crustuliniforme, an ectomycorrhizal partner of spruce; (2) Suillus variegatus, an ectomycorrhizal fungus incompatible with spruce; (3) Heterobasidion annosum, a spruce pathogen. Activity staining after SDS-PAGE and western blotting showed an accumulation of an ionically wall-bound 38-kDa peroxidase isoform. In addition, two covalently wall-bound isoforms (34 and 53 kDa) that could be released from spruce cell walls by cellulase and pectinase treatment were also induced by elicitors from these fungi. Moreover, in cells cultured without auxins all the elicitors triggered a rapid and transient accumulation of ionically wall-bound peroxidases, which reached a maximum activity 48 h after elicitor application. This early and transient peroxidase accumulation was diminished and delayed in cells cultured in the presence of auxins. In contrast, activity of peroxidases released into the culture medium of spruce cells or into the medium of protoplasts was suppressed by the elicitors of Hebeloma crustuliniforme. However, this suppression was attenuated by the action of auxins. It is suggested that under natural conditions, in infected spruce roots, the elicitors of the compatible fungus cause both suppression of the peroxidase (which is secreted to the free space of the roots), and induction of wall-bound and symplasmic peroxidases. On the other hand, auxins synthesized by the fungus could weaken these different elicitor-mediated effects.     

Increase of embryogenic callus formation in cucumber by initial culture on high concentration of 2,4-dichlorophenoxyacetic acid

Cucumber (Cucumis sativus L.) leaf explants were cultured either continuously on standard medium containing 4.5 µM 2,4- dichlorophenoxyacetic acid (2,4-d) and 4.4 µM benzylaminopurine, or first cultured for various periods at different levels of 2,4-d, picloram or naphthaleneacetic acid (NAA), and then transferred to standard medium. When cultured continuously on standard medium, less than 10% of the explants formed embryogenic callus. Initial culture on picloram or NAA, or on 2,4-d at a low concentration (1.4 µM) did not result in any embryogenic callus formation. Embryogenic callus formation increased to 40% if during the initial phase of the culture (10 days), the 2,4-d concentration was raised to 14 µM. Prolonged culture on 14 µM 2,4-d resulted in less embryogenic callus formation.Abbreviations BA benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid     

Effect of morphactin on certain plant growth substances in bean roots

The effect of morphactin (methyl-2-chloro-9-hydroxyfluorene-9-carboxylate) on the content of several plant growth substances in bean roots was determined. Beans (Phaseolus vulgaris L. cv. Spartan) were soaked in aqueous solutions of morphactin, 1 x 10^-4, 1 x 10^-5, and 1 x 10^-6M and grown in moist vermiculite. As controls were used beans grown in water-moistened vermiculite either intact or having the root tips removed (decapped). The roots, morphactin-treated, controls, and the decapped ones were analyzed for indol-3-yl acetic acid (IAA), indol-3-yl acrylic acid (IAcA), indol-3-yl pyruvic acid (IPyA), indol-3-yl lactic acid (1LA), abscisic acid (ABA), gibberellins GA₁, GA₃, GA₄, and GA₉ using gas-liquid chromatographic methods. Morphactin, while affecting the geotropical responses, changed also the growth substance content of roots. IAA, ABA, GA₁, and GA₉ contents decreased, IPyA, IAeA, GA₃, and GA₄ contents were not affected and ILA content increased slightly with increasing dosages of morphactin. Growth substance pattern of decapped roots resembled that of the roots treated with the highest dose, 1 x 10^-4M, of morphactin.     

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.     

激素信号在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。     

Growth stimulation in bean (Phaseolus vulgaris L.) by Trichoderma

Trichoderma species are commonly used as biological control agents against phytopathogenic fungi and some strains are able to produce metabolites that enhance plant growth. In the current study we evaluated the production of potential growth-promoting metabolites, rhizosphere competence and endophytism for 101 isolates of Trichoderma from Colombia, and assessed the relationship of these factors to the enhancement of early stages of growth on bean seedlings. Twenty percent of these Trichoderma strains were able to produce soluble forms of phosphate from phosphoric rock. Only 8% of the assessed strains showed consistent ability to produce siderophores to convert ferric iron to soluble forms by chelation. Sixty percent of isolates produced indole-3-acetic acid (IAA) or auxin analogues. The production of any of these metabolites was a characteristic of specific strains, as the ability to produce these metabolites varied greatly within species. Moreover, the production of these substances did not correlate with enhanced growth on bean seedlings, measured as the combined increase in length of roots and aerial parts in the V3 stage of growth. Seven Trichoderma isolates significantly improved the growth of bean seedlings. However, metabolite production varied widely in these seven strains, and some isolates did not produce any of the assessed growth-promoting metabolites. Results indicated that growth was enhanced in the presence of rhizosphere competent and endophytic strains of Trichoderma, and these characteristics were strain-specific and not characteristic for species.     

Measurement of the extent of somaclonal variation in begonia plants regenerated under various conditions. Comparison of three assays

Begonia plants were regenerated from leaf explants treated with increasing concentrations of the chemical mutagen nitrosomethylurea (NMU). In these plants, we evaluated three methods to assess the extent of variation: a qualitative, phenotypic assay (the percentage of aberrant plants), a molecular assay (changes in RAPD patterns) and a quantitative, phenotypic assay (variation in a quantitative trait). The qualitative, phenotypic assay required a large number of plants per treatment (approx. 100) and careful, skilled judgement. It was sensitive to physiological variation. The RAPD assay was not sufficiently sensitive: even at the highest NMU concentration there were no changes in RAPD patterns. The quantitative, phenotypic assay gave the best results: it was simple, objective and sensitive, and required few plants per treatment (approx. 30). Plants were also regenerated from different types of intermediate callus, and their variation was assessed. The performance of the three assays was essentially the same as with plants obtained after mutagenesis with NMU. An intermediate nodular- or non-nodular-callus phase resulted in slightly or strongly increased variation, respectively. In contrast to NMU-induced variation, callus-related variation, as determined in the quantitative, phenotypic assay, appeared to be to a large extent transient since it decreased strongly after a second direct-regeneration step. An intermediate callus phase resulted in 2.5% juvenile plants. This aberration, which might be related with changes in the methylation status of DNA, was not observed in NMU-treated plants. Received: 30 January 2000 / Accepted: 14 April 2000     

Hormone-like effect of vascular tissue on starch accumulation in stem explants of kale, Brassica oleracea

Explants of stem pith of kale ( Brassica oleracea L. var. medullosa cv. Krasa), cultured for several days on agar medium containing sucrose, accumulate starch. Application of streptomycin, 5-fluorouracil and other inhibitors indicates that starch accumulation depends on protein synthesis on 80 S ribosomes. If explants derived from plants grown under natural long-day conditions contained vascular tissue, including cambium, in addition to pith parenchyma, the amount of starch formed in the pith tissue increased up to seven fold when compared with explants without vascular tissue. Similar increase of starch content as caused by vascular tissue was achieved by the addition of kinetin or trans -zeatin (10 μ) in the presence of 5 μ indole-3-acetic acid or 1-naphthaleneacetic acid. A further three-fold increase in starch accumulation could be achieved by application of cytokinin and auxin to explants containing vascular tissue. When explants were derived from plants grown under natural short-day conditions cytokinins and auxins had little or no effect, but vascular tissue enhanced starch formation significantly. The spreading of starch inducing stimulus from vascular tissue (probably from its meristematic region) to the pith parenchyma up to a distance of at least 20 mm was demonstrated. It was concluded that a hormone-like factor other than cytokinin and auxin was involved in the stimulatory action of vascular tissue. The effects of this factor on protein accumulation and growth in the explants and its possible production by meristematic tissues in vivo are discussed.     

The influence of auxins on transformation of wheat and tritordeum and analysis of transgene integration patterns in transformants

 Although it is possible to transform wheat, broad application of the technology is limited because of the low overall efficiency and the lack of reliability of the technique. In addition there is little published data on transgene integration patterns and inheritance in wheat. We have generated a population of transgenic wheat and tritordeum lines under different auxin regimes and show that, under the conditions described, the presence of picloram results in higher transformation efficiencies than the presence of 2,4-D. Molecular analysis shows low-copy numbers and simple integration patterns to be prevalent in the transgenic lines. Mendelian inheritance of transgenes in T ₁ progeny was observed for the majority of lines. Received: 2 December 1997 / Accepted: 12 March 1998     

一种新的生根测定方法

研究生长素类的生根现象和筛选生根促进物质,一直沿用幼苗茎切段的生根试法。但是这些测定方法操作比较复杂,试验误差也较大,而且经常出现不规律的结果,因此不适于生根现象的研究和众多样品的筛选工作。我们在工作中找到了一种以离体黄瓜子叶为试验材料的良好生根测定方法,国内外尚未见报道。我们曾利用这一方法研究了某些植物生长调节活性物质的生根作用,并在筛选生根促进物质中得到了较好的结果。本文报道这一新的生根测定方法。