小麦叶绿体基因组定点整合表达载体的构建

从小麦中分别克隆了包括rbcL基因3′端部分和完整的psaI、ycf4基因的DNA片段.利用克隆到的DNA片段作为同源重组片段、烟草叶绿体16S rRNA基因的启动子Prrn和PsbA基因的终止子PsbA3′控制筛选标记基因aadA和报告基因gfp的转录,构建了小麦叶绿体基因组定点整合表达载体pRAGY. 用该载体转化大肠杆菌,在激光扫描共聚焦显微镜下,检测到了gfp基因成功表达的产物被激发出的强烈的绿色荧光.     

发酵麸皮多糖酶辅助提取工艺优化及其生物活性研究

通过响应面法优化提取发酵麸皮多糖的工艺,并评价其体外益生和抗氧化活性。以发酵麸皮多糖的得率为响应值,采用纤维素酶酶解与水浴浸提相结合的方法提取发酵麸皮多糖,以纤维素酶添加量、料液比、水浴浸提温度、水浴浸提时间为试验因素建立数学模型,筛选最佳提取工艺条件。通过测定还原力、DPPH和·OH自由基的清除能力对比发酵和未发酵麸皮多糖的体外抗氧化活性,并通过测定嗜酸乳杆菌、植物乳杆菌、两歧双歧杆菌的生长对比发酵和未发酵麸皮多糖的体外益生活性。结果表明,发酵麸皮多糖最佳提取工艺为:料液比1∶16(w/v),酶添加量1 000 U/g,水浴浸提温度90℃,水浴浸提时间60 min,在此条件下发酵麸皮多糖的得率实测值为73. 35%。发酵麸皮多糖具有较强的DPPH和·OH自由基的清除能力,可促进嗜酸乳杆菌、植物乳杆菌和两歧双歧杆菌的生长。     

耐盐性不同的小麦根和根茎结合部的拒Na~ 作用

NaCl处理引起小麦幼苗干重下降 ,盐敏感品种比耐盐品种下降幅度要大。盐敏感品种的拒Na 能力为 35 %左右 ,耐盐品种的拒Na 能力为 5 0 %～ 6 0 %左右 ,这表明耐盐品种的拒Na 能力远远大于盐敏感品种。不同耐盐性小麦的拒Na 部位不同 ,盐敏感品种的拒Na 部位主要在根茎结合部 ,而耐盐品种的拒Na 部位主要在根部     

小麦耐盐种质的筛选鉴定和耐盐基因的标记

通过对 40 0份材料的芽期、苗期鉴定 ,筛选出 11份耐盐性较强的普通小麦 (TriticumaestivumL .)、小麦和黑麦 (SecalecerealeL .)、小麦和延安赖草 (Leymuschinensis (Trin .)Tzvel.)杂交后代材料 ,其中耐盐性突出的材料有 :普通小麦品种“红蚂蚱”、“科遗 2 6”、“希望”(Hope) ;小麦与黑麦杂交后代材料 98_46、98_113、98_131;小麦与延安赖草杂交后代材料 98_16 0、98_16 1、98_16 3。耐盐性表现最突出的材料是 98_113和 98_16 0。细胞学鉴定和原位杂交及醇溶蛋白酸性聚丙烯酰胺凝胶电泳 (A_PAGE)分析和低分子量谷蛋白SDS_PAGE分析 ,证明 98_113是稳定的小麦 黑麦二体附加系 ,但具体附加的是黑麦的哪条染色体还不清楚 ;98_131是小麦 黑麦 1B/ 1R易位系。结合其他 1B/ 1R材料的耐盐表现 ,提出了黑麦 1R染色体短臂上存在耐盐基因的可能性。对 (98_16 0×BanacakaMska)F2 代分离群体苗期抗盐鉴定分析 ,表明在这一杂交组合中的耐盐性状可能由一个主效基因控制。应用SSR标记技术 ,筛选到了与 98_16 0耐盐性状连锁的SSR标记WMS6 7和WMS2 13,它们与耐盐基因的遗传距离分别为 13.9cM (centMorgan)和 31.0cM。结合小麦SSR图谱分析 ,将该主效抗性基因定位在 5BL上。     

Testing the responses of four wheat crop models to heat stress at anthesis and grain filling

Higher temperatures caused by future climate change will bring more frequent heat stress events and pose an increasing risk to global wheat production. Crop models have been widely used to simulate future crop productivity but are rarely tested with observed heat stress experimental datasets. Four wheat models (DSSAT‐CERES‐Wheat, DSSAT‐Nwheat, APSIM‐Wheat, and WheatGrow) were evaluated with 4 years of environment‐controlled phytotron experimental datasets with two wheat cultivars under heat stress at anthesis and grain filling stages. Heat stress at anthesis reduced observed grain numbers per unit area and individual grain size, while heat stress during grain filling mainly decreased the size of the individual grains. The observed impact of heat stress on grain filling duration, total aboveground biomass, grain yield, and grain protein concentration (GPC) varied depending on cultivar and accumulated heat stress. For every unit increase of heat degree days (HDD, degree days over 30 °C), grain filling duration was reduced by 0.30–0.60%, total aboveground biomass was reduced by 0.37–0.43%, and grain yield was reduced by 1.0–1.6%, but GPC was increased by 0.50% for cv Yangmai16 and 0.80% for cv Xumai30. The tested crop simulation models could reproduce some of the observed reductions in grain filling duration, final total aboveground biomass, and grain yield, as well as the observed increase in GPC due to heat stress. Most of the crop models tended to reproduce heat stress impacts better during grain filling than at anthesis. Some of the tested models require improvements in the response to heat stress during grain filling, but all models need improvements in simulating heat stress effects on grain set during anthesis. The observed significant genetic variability in the response of wheat to heat stress needs to be considered through cultivar parameters in future simulation studies.     

The activity and stability of wheat nitrate reductase in vitro

The activity and decay characteristics of nitrate reductase from wheat (Triticum aestivum) were studied in crude, partially-purified and highly-purified preparations. The decay of nitrate reductase activity in crude extracts was due to spontaneous dissociation of the enzyme and to the effects of two decay factors, one present in the 0–30% and the other in the 50–70% saturated (NH₄)₂SO₄ fraction of a crude extract. Low rates of factor-mediated NR decay in vitro were associated with high levels of NR activity in vivo.     

Settlement of the diazotrophic,phytoeffective bacterial strain Pantoea agglomerans on and within winter wheat: An investigation using ELISA and transmission electron microscopy

The aim of this study was to investigate the ability of Pantoea agglomerans, a plant growth-promoting bacterium, to colonize various regions and tissues of the wheat plant (Triticum aestivum L.) by using different inoculation methods and inoculum concentrations. In addition, the enzyme-linked immunosorbent assay (ELISA) and transmission electron microscopy (TEM) were used to determine: (a) the ability of the bacterial cells to grow and survive both on the surface and within internal tissue of the plant and (b) the response of the plant to bacterial infection. After inoculation, cells of the diazotrophic bacterial strain P. agglomerans were found to be located in roots, stems and leaves. Colony development of bacterial cells was only detected within intercellular spaces of the root and on the root surface. However, single bacterial cells were observed in leaves and stems on the surface of the epidermis, in the vicinity to stomatal cells, within intercellular spaces of the mesophyll and within xylem vessels. Inoculated bacterial cells were found to be able to enter host tissues, to multiply in the plant and to maintain a delicate relationship between endophyte and host. The density of bacterial settlement in the plant in all experiments was about 10⁶ to 10⁷ cells per mL root or shoot sap. Establishment was confirmed by a low coefficient of variation of ELISA means at these concentrations.     

The effects of endogenous cytokinin content on benzyladenineenhanced nitrate reductase induction

Foliar application of benzyladenine (BA) has been shown to enhance nitrate-dependent induction of nitrate reductase (NR; EC 1.6.6.1) in etiolated wheat ( Triticum aestivum L.) seedlings. Whether similar enhancement occurs in light-grown plants, or whether endogenous cytokinin content affects this enhancement is unknown. Since the cytokinin content of etiolated plants probably differs from that of light-grown seedlings, the NR response of each to exogenous root- or shoot-applied BA in wheat (cv. Red Bob) was examined. Endogenous cytokinins present in untreated control tissues prior to BA application and changes that occurred after a 22 h (12 h dark followed by 10 h of light) period were determined using a combined HPLC-immunoassay method. Shoot application of BA enhanced the induction of NR in etiolated seedlings in a concentration-dependent manner but failed to enhance NR induction in light-grown plants. Root-applied BA enhanced NR induction in both etiolated and light-grown seedlings. Endogenous root cytokinin levels were similar in both etiolated and light-grown plants. In contrast, shoots of 6 day-old light-grown seedlings contained at least 20 times the amount of total cytokinins measured in shoots from etiolated plants of the same age. Total cytokinin content of the light-grown plants diminished after the 22-h period while that measured in etiolated seedlings increased. The responsiveness of seedlings to BA was correlated with endogenous cytokinin levels in that enhancement of NR induction by exogenous BA was low in tissues which contained high concentrations of cytokinin at the time of BA application. These results may prove useful in interpretation of gene responses to exogenous plant growth regulators.     

小麦幼苗根系镉螯合素

从经Cd~(2+)处理的小麦幼苗根系中分离得到一种镉结合复合物(Cd-BC)。通过SephadexG75,DEAE-52柱层析纯化,鉴定了此复合物性质:(1)紫外吸收光谱在255～265 tim间有一个“肩”,A_(250)/A_(280)>1;(2)在Sephadex G75柱层析上的表观分子量约为10kD,但在SDS-聚丙烯酰胺凝胶电泳上呈现的条带紧接着前沿,分子量非常小;(3)氨基酸组分分析,约90％的氨基酸残基为Glu/Gln,Cys和Gly,三者比例约为4:4:1。结果说明小麦幼苗根系Cd-BC是寡聚肽,是植物镉螯合素(Cd-PCs)的聚合体。     

Interaction of drought and high temperature on photosynthesis and grain-filling of wheat

Drought and high temperature often occur simultaneously, but their effects on crops are usually investigated individually. Our objective was to compare effects of drought, high temperature, and their interactions on photosynthesis and grain-growth of wheat (Triticum aestivum L.). Plants (cv. Len) were grown uniformly in well-watered soil at 25/20 ± 2 °C day/night until anthesis, when they were subjected to regimes of no drought (soil at field capacity) and drought (plant water potential of –.0 to –2.4 MPa) at 15/10, 25/20, and 35/30 °C in controlled environments until physiological maturity. Drought decreased photosynthesis, stomatal conductance, viable leaf area, shoot and grain mass, and weight and soluble sugar content of kernels but increased plant water-use efficiency. High temperature hastened the decline in photosynthesis and leaf area, decreased shoot and grain mass as well as weight and sugar content of kernels, and reduced water-use efficiency. Interactions between the two stresses were pronounced, and consequences of drought on all physiological parameters were more severe at high temperature than low temperature. The synergistic interactions indicated that productivity of wheat is reduced considerably more by the combined stresses than by either stress alone, and that much of the effect is on photosynthetic processes.