Cytochalasins from Phoma exigua var. Heteromorpha

Three further cytochalasins fromPhoma exigua var. heteromorpha, grown on wheat, were isolated and characterized by spectroscopic methods and by chemical correlation with cytochalasin B. They were identified as cytochalasin T, a new 24-oxa[14]cytochalasan, cytochalasin F and 7-O-acetylcytochalasin B, both isolated for the first time from this fungus. Cytochalasin F showed significant activity in the brine shrimp assay and on tomato seedling growth.     

华重楼离体胚培养及植株再生初探

为探明华重楼离体胚培养及植株再生的基本体系,该文以华重楼离体幼胚为试验材料,以MS培养基为基本培养基,研究不同光照、不同浓度梯度组合的植物生长调节剂对华重楼离体幼胚萌发、成苗的影响。结果表明:培养到60 d时,暗培养条件下华重楼离体幼胚的生长率和萌发率分别比光培养条件下高45.25%、19.17%,故暗培养比光培养更有利于华重楼离体幼胚生长发育。当GA₃浓度相同时,离体幼胚萌发所需时间随IAA浓度增加而延长。不同浓度的GA₃都可促进离体幼胚萌发,促进作用由强到弱依次为5 mg·L^-1GA₃>1 mg·L^-1GA₃> 10 mg·L^-1GA₃。在黑暗条件下,优选得到最适华重楼离体幼胚生长发育配方为1/2 MS+30g·L^-1蔗糖+7 g·L^-1琼脂+0.5 g·L^-1活性炭+5 mg·L^-1GA₃     

两种广西特有报春苣苔属(苦苣苔科)植物传粉生物学研究

通过野外观察和室内试验,对两种广西特有的桂林小花苣苔和阳朔小花苣苔的传粉生物学进行比较研究。结果表明:两种报春苣苔属植物花期从7月底至8月初;单花花期内花粉具有较高的活性,最高可达92.6%和94.5%;柱头可授性最高时可达90%和95%;花粉/胚珠比率(P/O)分别为110.28±17.45和229.65±18.00;柱头与花药之间存在着空间隔离,可防止自花授粉;在单花花冠裂片张开后第3天,花药开始散粉,但雌蕊在花朵刚开始开放时已伸长,待第3天时柱头已伸长到位于花冠筒口部,高于花药,便于接受异花花粉;该两种植物均不存在无融合生殖现象;两种报春巨苔属植物均高度自交亲和,但很难发生自发的自花授粉,必须依靠外力,因此传粉媒介对于结实率有重要影响,自然条件下基本不发生自花授粉;在自然状态下结实率明显低于两种人工授粉的结实率;小蜂和淡脉隧蜂是目前已知仅见的两种传粉者。     

Putaminoxin, a phytotoxic nonenolide from Phoma putaminum

Phoma putaminum, the causal agent of leaf necrosis of Erigeron annuus, a common weed of field and pasture, produced toxic metabolites when grown in liquid culture. The main phytotoxin, named putaminoxin, was isolated and characterized using spectroscopic and chemical methods as (5S)5-hydroxy-9-propyl-6-nonen-9-olide, a new 10-macrolide. When assayed on leaves of host and non-host plants, putaminoxin showed a wide range of toxicity, with leaves of E. annuus being most sensitive.     

Plant colonization and environmental fate of the biocontrol fungus Phoma macrostoma

Several isolates of the fungus Phoma macrostoma demonstrated bioherbicidal activity against dandelion seedlings when applied to soil. Weed control ranged from 36 to 100% depending on the isolates and the doses applied. Using microbiological and molecular genetic techniques, the ability of these isolates to colonize target, and nontarget plants and to disperse and persist in soil were determined. PCR primers highly specific to the biocontrol isolates of P. macrostoma, were used to detect the isolates at rates of application between 4 and 1000 g/m². Based on the results from representative isolates tested, it was concluded that P. macrostoma colonized root tissues of both resistant and susceptible crop species and a susceptible weed species grown in treated soil, and the frequency of fungal isolation declined with time. It was occasionally detected on untreated plant tissues, which may have resulted from either natural occurrences on seed, or contamination of soil. The biocontrol fungus appeared to have limited mobility in the soil since it was not often detected away from the area where it was placed. It persisted in the soil at detectable levels for up to 4 months, but then its presence declined with time. One year post application, P. macrostoma was either not present or significantly reduced in both soil and plant samples depending on the year of sampling. The results suggested that the isolates of P. macrostoma used for biological weed control would have minimal environmental impact due to its ubiquitous nature, limited mobility, and weak persistence over seasons.     

Colletotrichum acutatum var. fioriniae (teleomorph: Glomerella acutata var. fioriniae var. nov.) infection of a scale insect

An epizootic has been reported in Fiorinia externa populations in New York, Connecticut, Pennsylvania and NewJersey. Infected insects have profuse sclerotial masses enclosing their bodies. The most commonly isolated microorganism from infected F. externa was Colletotrichum sp. A morphological and molecular characterization of this fungus indicated that it is closely related to phytopathogenic C. acutatum isolates. Isolates of Colletotrichum sp. from F. externa in areas of the epizootic were similar genetically and were named Colletotrichum acutatum var. fioriniae var. nov, based on our findings. In vitro and in planta mating observed between isolates of C. acutatum var. fioriniae could serve as a possible source of genetic variation and might give rise to new biotypes with a propensity to infect insects. Only one other strain, C. gloeosporioides f. sp. ortheziidae, has been reported to show entomopathogenic activity.     

Growth and isoflavonoid accumulation of Pueraria candollei var. candollei and P. candollei var. mirifica cell suspension cultures

We established cell suspension cultures derived from leaf, stem, and root calli of Pueraria candollei var. candollei and P. candollei var. mirifica using liquid Murashige and Skoog (MS) medium supplemented with 0.56 μM 6-benzyladenine (BA) and 4.52 μM 2,4-dichlorophenoxyacetic acid (2,4-D). Growth of the cell suspension cultures progressed to the stationary phase within 15–24 days. Methanolic extracts of cell suspension cultures of both varieties of P. candollei were analyzed using a validated HPLC protocol. All cell lines derived from leaf, stem, and root explants produced four major isoflavonoids: daidzein, daidzin, genistein, and genistin; these isoflavonoids were detected only in the roots of intact plants. Furthermore, the isoflavonoid contents of the cell suspension cultures were higher than those of intact plants. Thus, cell suspension culture of both varieties of P. candollei may be an effective tool for isoflavonoid production.     

Enhancement of taxane production in hairy root culture of Taxus x media var. Hicksii

This study assessed the effect of two precursors (l-phenylalanine and p-amino benzoic acid) used alone or in combination with methyl jasmonate, on the growth and accumulation of paclitaxel, baccatin III and 10-deacetylbaccatin III in hairy root cultures of Taxus x media var. Hicksii. The greatest increase in dry biomass was observed after 4 weeks of culturing hairy roots in medium supplemented with 1 μM of l-phenylalanine (6.2 g L⁻¹). Addition of 1 μM of l-phenylalanine to the medium also resulted in the greatest 10-deacetylbaccatin III accumulation (422.7 μg L⁻¹), which was not detected in the untreated control culture. Supplementation with 100 μM of l-phenylalanine together with 100 μM of methyl jasmonate resulted in the enhancement of paclitaxel production from 40.3 μg L⁻¹ (control untreated culture) to 568.2 μg L⁻¹, the highest paclitaxel content detected in the study. The effect of p-amino benzoic acid on taxane production was less pronounced, and the highest yield of paclitaxel (221.8 μg L⁻¹) was observed when the medium was supplemented with 100 μM of the precursor in combination with methyl jasmonate.Baccatin III was not detected under the conditions used in this experiment and the investigated taxanes were not excreted into the medium.     

The effects of Phoma macrostoma on nontarget plant and target weed species

Phoma macrostoma 94-44B was evaluated against 94 plant species in 34 botanical families, of economically important agricultural, horticultural and ornamental species, as well as target and nontarget weeds. Fifty-seven species from 28 families were found to be resistant to P. macrostoma, while 38 species from 12 families, six of which also contained resistant species, were found to be susceptible. Those families comprising both susceptible and resistant species included the Asteraceae, Brassicaceae, Fabaceae, Lamiaceae, Plantaginaceae and Rosaceae with the foremost three containing the largest numbers of susceptible species. P. macrostoma was pathogenic to many dicotyledonous plant species, but nonpathogenic to monocots. Commercial applications for weed management in turfgrass, agriculture, horticulture and forestry seem probable, while domestically management of weeds in lawns, transplanted ornamental and annual flowering species may provide alternative markets.     

Immunomodulating polysaccharides from the lichen Thamnolia vermicularis var. subuliformis

Three heteroglycans Ths-4, Ths-5 and thamnolan and a beta-glucan, Ths-2, isolated from the lichen Thamnolia vermicularis var. subuliformis were tested for in vitro immunomodulating activities and shown to have various influences on the immune system. All the polysaccharides except Ths-4 caused a stimulation of rat spleen cell proliferation. In contrast, Ths-4 caused cell death early in the culture, probably due to over-stimulation. Moreover, the galactofuranomannans, Ths-4, Ths-5 and the beta-glucan Ths-2, induced rat spleen cells to secrete IL-10 significantly above background levels. In addition, Ths-4 and Ths-5 stimulated significant TNF-alpha secretion by rat peritoneal macrophages. The galactofuranomannans Ths-4 and Ths-5 have similar structures apart from the molecular weight. Thus, it may be concluded that the molecular size might influence the potency but not the pattern of activity for Ths-4 and Ths-5. The galactofuranorhamnan thamnolan had less mitogenic effect than Ths-5 and Ths-2 and neither induced IL-10 secretion by rat spleen cells nor TNF-alpha secretion by peritoneal macrophages to significant levels. This shows that thamnolan with its unusual galactofuranorhamnan structure differs from the other Thamnolia polysaccharides in its immunomodulatory activity.     

Embryological Studies on Narcissus tazetta var. chinensis

Chinese narcissus (Narcissus tazetta var. chinensis Roem) blooms but has no seeds. Embryological studies on the species were conducted to discover the causes of its sterility. Its anther wall is composed of four layers of cells, and its tapetum is of the secretory type. The cytokinesis of microspore mother cells is of the successive type, and the tetrad is tetrahedral. During meiosis of microspore mother cells, some chromosomes lagged, and several micronuclei were found in tetrads. Only 27.7% of the pollen grains contained full cytoplasm, and 1.3% of them germinated in culture medium. No pollen grain, however, could germinate on the stigma. The ovary is trilocular with axile placenta, and the ovules are bitegmic, tenuinucellate, and anatropous. Its embryo sac is of the polygonum type. Most embryo sacs degenerated, and only about 4.5% of the ovules contained a normal embryo sac with an egg cell, two synergids, three antipodal, and a central cell containing two polar nuclei. One reason for the sterility of Chinese narcissus is the abnormality of microsporogenesis and megasporogenesis, in which only a few functional pollen grains and embryo sacs are produced. The other reason is that the pollen grains cannot germinate on the stigma. This paper was translated from Journal of Xiamen University (Natural Science), 2005, 44(1) (in Chinese)