Increased levels of glycerol-3-phosphate lead to a stimulation of flux into triacylglycerol synthesis after supplying glycerol to developing seeds of<Emphasis Type="Italic"> Brassica napus</Emphasis> L.<Emphasis Type="Italic"> in planta</Emphasis>

Glycerol-3-phosphate (glycerol-3P) is a primary substrate for triacylglycerol synthesis. In the present study, changes in the levels of glycerol-3P during rape (Brassica napus L.) seed development and the influence of manipulating glycerol-3P levels on triacylglycerol synthesis were investigated. (i) Glycerol-3P levels were high in young seeds and decreased during seed development at 30 and 40 days after flowering (DAF), when lipid accumulation was maximal. (ii) To manipulate glycerol-3P levels in planta, various concentrations of glycerol were injected directly into 30-DAF seeds, which remained otherwise intact within their siliques and attached to the plant. Injection of 0–10 nmol glycerol led to a progressive increase in seed glycerol-3P levels within 28 h. (iii). Increased levels of glycerol-3P were accompanied by an increase in the flux of injected [¹⁴C]sucrose into total lipids and triacylglycerol, whereas fluxes to organic acids, amino acids, starch, protein and cell walls were not affected. (iv) When [¹⁴C]acetate was injected into seeds, label incorporation into total lipids and triacylglycerol increased progressively with increasing glycerol-3P levels. (v) There was a strong correlation between the level of glycerol-3P and the incorporation of injected [¹⁴C]acetate and [¹⁴C]sucrose into triacylglycerol. (v) The results provide evidence that the prevailing levels of glycerol-3P co-limit triacylglycerol synthesis in developing rape seeds.Abbreviations DAF Days after flowering - DAG Diacylglycerol - G3PAT Glycerol-3-phosphate acyltransferase - Glycerol-3P Glycerol-3-phosphate - PA Phosphatidic acid - PC Phosphatidylcholine - TAG Triacylglycerol,     

Novel bacterial diversity recovered from the rhizosphere of oilseed rape (Brassica napus) determined by the analysis of 16S ribosomal DNA

Soil was sampled to a distance of 2.5 mm beneath a root mat of oilseed rape (Brassica napus) in a model rhizosphere system. DNA was extracted and the 16S rDNA amplified, cloned and sequenced. Phylogenetic analysis of these sequences with those held on-line, revealed that 37% of the clones fell within the Holophaga / Acidobacterium phylum, 17% were within the proteobacteria, 14% of the clones were close relatives of Bacillus megaterium and 5% were related to Verrucomicrobium spinosum. An additional eleven clones (21%) could not be assigned to any known phylum and may represent novel bacterial lineages. This study highlights the diverse nature of rhizosphere soils and reinforces the role that molecular approaches play in unravelling such diversity.     

抗草丁膦和抗草甘膦转基因油菜的抗性基因向野芥菜的流动

通过人工去雄授粉和田间隔行种植试验,研究了抗草丁膦和抗草甘膦转基因油菜(Brassica napus)中的bar基因和EPSPS基因向野芥菜(B. juncea var. gracilis)流动的可能性。结果表明在人工授粉的情况下,以野芥菜为母本,分别以两种转基因油菜为父本,亲和性指数都很高,达13以上,与野芥菜自交或开放授粉条件下的亲和性指数没有明显差异,说明两种转基因油菜和野芥菜的亲和性较好。经两次除草剂筛选,人工杂交获得的所有F₁对相应的除草剂都表现出了明显的抗性,且经PCR检测扩增出了各自的特异性条带,说明人工杂交获得的所有F₁都携带了相应的抗性基因。F₁的适合度研究表明,两种F₁种子萌发率和母本都没有明显差异,营养生长明显好于母本。但花粉活力和结实率明显下降,携带抗草丁膦基因F₁的花粉活力和每角果粒数分别是32.4%和0.59粒,携带抗草甘膦基因F₁的花粉活力和每角果粒数分别是35.1%和0.58粒。经两次除草剂筛选和PCR检测,表明野芥菜和抗草丁膦油菜或与抗草甘膦油菜田间隔行种植分别能产生0.02%和0.014%的携带抗性基因的F₁杂种。以上结果表明抗除草剂转基因油菜的抗性基因具有向野芥菜流动的可能性,且bar和EPSPS基因向野芥菜流动的可能性类似,但对其可能引起的环境后果需要做进一步地深入研究。     

Availability of different forms of sulphur fertilisers to wheat and oilseed rape

A pot experiment was conducted to compare the availability and efficiency of three sulphur (S) fertilisers to wheat in the first year and oilseed rape in the second year, using six agricultural soils. Four treatments were applied in the initial year: control (no S), two forms of elemental S (either micronised S° particles or a bentonite + S° mixture) and a sulphate fertiliser (ammonium sulphate). In the first year, the micronised S° was as effective as the sulphate fertiliser, both producing similar increases of wheat grain yield (on average 36%) and S uptake (on average 164%) over the control. In contrast, responses to the bentonite + S° form were minimal, indicating a limited S supply. In the second year the control treatment failed to produce seeds in most soils, whereas the micronised S° and sulphate treatments increased seed yields of oilseed rape to an average of 13.4 and 12.9 g pot^-1, respectively. The performance of the bentonite + S° varied between soils: two soils produced yields similar to those of the other S fertilisers, while the remaining soils had low yields. To test whether the poor performance of the bentonite clay + S° fertiliser was due to the lack of exposure of the prills to physical weathering in the glasshouse, the effect of freeze-thaw action on the fertilisers performance was assessed in a separate pot experiment. The responses in wheat yield and S uptake showed that freeze-thaw did not enhance the physical disruption of the prills or fertiliser effectiveness. These results suggest that the release of available S from the bentonite + S° mixture was too slow to meet the requirement of wheat and oilseed rape. This revised version was published online in June 2006 with corrections to the Cover Date.     

A- or C-chromosomes, does it matter for the transfer of transgenes from Brassica napus

Introgression of genes from allotetraploid Brassica napus into its diploid wild relative B. rapa is generally considered to be inevitable. As a means to minimize a potential ecological risk in environments where B. rapa is growing, the insertion of transgenes into chromosome regions of B. napus with a very low probability of transfer to backcross generations with B. rapa has been proposed. Recently, the progeny of four backcross generations between transgenic herbicide-tolerant B. napus and B. rapa was studied in selection experiments (Metz et al. 1997). The rapid decrease in the frequency of herbicide-tolerant plants was explained by selection against the C-chromosomes of B. napus in favor of the homeologous A-chromosomes. Obviously, such C-chromosomes could be potential candidates as safe integration sites for transgenes. We considered these safety aspects using a simple population genetic model. Theory and experiments, however, do not favor the chromosomes of B. napus as safe candidates with respect to the introgression of transgenes into wild populations of B. rapa. Received: 5 July 1999 / Accepted: 29 July 1999     

Assessment of interspecific hybridization between transgenic oilseed rape and wild radish under normal agronomic conditions

In order to assess the hybridization rate between oilseed rape and wild radish under normal agronomic conditions, three 1-ha field experiments were performed. In each case, wild radish plants were transplanted at different densities in the middle, the border, or the margin of the herbicide-tolerant oilseed rape field. Among the 189084 seedlings obtained from seeds harvested on wild radish plants, only one herbicide-tolerant interspecific hybrid (RrRrAC, 2n = 37) was characterized from seeds harvested on an isolated plant growing in the margin of the field. Thus, for the wild radish total harvest, with a 95% confidence limit, the frequency of interspecific hybrids was assessed to range from 10^–7 to 3.10^–5. Interspecific hybrids were detected in all cases among the smallest seeds with a diameter less than 1.6 mm harvested on oilseed rape, but the highest frequency was obtained from oilseed rape close to wild radish plants growing as clusters in the border or the margin of the field. Most hybrids had the expected triploid genomic structure (ACRr, 2n = 28) except for four amphidiploids (AACCRrRr, 2n = 56) and one hybrid from a wild radish unreduced gamete (ACRrRr, 2n = 37). Among the 73847 seedlings observed on the oilseed rape total harvest, the frequency of interspecific hybrids was assessed to range from 2.10^–5to 5.10^–4, with a 95% confidence limit. The results are discussed with regard to the type of oilseed rape variety used and the characteristics of the interspecific hybrids. Received: 5 October 1999 / Accepted: 11 November 1999     

Does the lack of vernalization requirement interfere with winter survival of oilseed rape plants?

Recent studies (Rapacz 1999) have shown that cultivars of spring-type oilseed rape are able to cold-acclimate to the level comparable with winter cultivars, but only after prehardening which results both in the increase of photosynthetic activity and in growth cessation. It is commonly known that under field conditions spring-type cultivars could not survive winter. Present studies were undertaken to explain the reasons for low winter hardiness of spring type rape plants. Six cultivars of spring and two of winter rape were sown in the open-air vegetation room at the end of August. The obtained results indicate that the degree of frost damage in spring-type plants increased in the course of winter and this increase was parallel to elongation of generative shoots observed after periods of warming. Each spring cultivar was completely killed by frost just after its generative shoot reached 15–20 cm, irrespective of its frost resistance level, determined previously under laboratory conditions. In the case of winter cultivars survival rate was consistent with laboratory-estimated frost resistance. It is suggested that spring rape could not survive winter because of its limited ability to prevent shoot elongation during winter at temperatures slightly above 0 °C. It was also found that less efficient photosynthetic electron transport in autumn was observed in these spring cultivars in which the elongation of generative shoots was observed already during the first warm break in winter.     

无融合生殖油菜AMR—1花托离体培养的研究

报道了不同激素浓度对无融合生殖没菜花托器官分化效果的研究,结果显示：（１）以ＭＳ为基本培养基,以带有子房和花柄的花托为外植体离体培养,花托、花柄切口部位直接芽诱导的最佳激素配比为４．０ｍｇ／Ｌ６－ＢＡ＋０．０１ｍｇ／Ｌ ＮＡＡ,频率为５８．８２％,花托、花柄部位先形成愈伤组织,继而分化出丛生芽的最佳激素配比为５．０ｍｇ／Ｌ ６－ＢＡ＋０．５ｍｇ／Ｌ ＮＡＡ,频率为８４．００％;（２）腋芽增殖的最佳     

转基因油菜的基因流及生态风险

综合评述了转基因油菜的基因流及其生态风险.油菜作为最早的转基因作物之一目前已在加拿大和澳大利亚大面积商业化应用.(常)异花授粉作物油菜的天然异交率可达30%左右,也易与其它芸苔属作物杂交,因此转基因油菜的生态风险已引起各国科学家的高度重视.转基因油菜主要通过与其野生近缘种的花粉交换和与非转基因油菜的花粉交换两种方式进行花粉的输出.基因可能逃逸到相关野生近缘种,但在大田环境下能够得到杂种的可能性很小;由于基因的漂流在油菜田块间确实存在,因此在种植转基因油菜的过程中必须考虑其间隔距离.     

Zinc induces distinct changes in the metabolism of reactive oxygen and nitrogen species (ROS and RNS) in the roots of two Brassica species with different sensitivity to zinc stress

Background and Aims Zinc (Zn) is an essential micronutrient naturally present in soils, but anthropogenic activities can lead to accumulation in the environment and resulting damage to plants. Heavy metals such as Zn can induce oxidative stress and the generation of reactive oxygen and nitrogen species (ROS and RNS), which can reduce growth and yield in crop plants. This study assesses the interplay of these two families of molecules in order to evaluate the responses in roots of two Brassica species under high concentrations of Zn.Methods Nine-day-old hydroponically grown Brassica juncea (Indian mustard) and B. napus (oilseed rape) seedlings were treated with ZnSO₄ (0, 50, 150 and 300 µm) for 7 d. Stress intensity was assessed through analyses of cell wall damage and cell viability. Biochemical and cellular techniques were used to measure key components of the metabolism of ROS and RNS including lipid peroxidation, enzymatic antioxidants, protein nitration and content of superoxide radical (O2·−), nitric oxide (NO) and peroxynitrite (ONOO⁻).Key Results Analysis of morphological root damage and alterations of microelement homeostasis indicate that B. juncea is more tolerant to Zn stress than B. napus. ROS and RNS parameters suggest that the oxidative components are predominant compared with the nitrosative components in the root system of both species.Conclusions The results indicate a clear relationship between ROS and RNS metabolism as a mechanism of response against stress caused by an excess of Zn. The oxidative stress components seem to be more dominant than the elements of the nitrosative stress in the root system of these two Brassica species.