Lectins from seeds of Crotalaria pallida (smooth rattlebox)

A lectin from the seeds of Crotalaria pallida (CPL), with an apparent molecular mass of 30 kDa, determined by SDS-polyacrylamide gel electrophoresis, showed human type A and B erythrocytes agglutination activity, which is inhibited by raffinose and galactose. The lectin requirement for divalent cation was demonstrated with EDTA/EGTA blocking hemagglutination activity. Although the N-terminal amino acid sequence of CPL is identical to another lectin from Crotalaria striata, which is taxonomically synonymous to Crotalaria pallida, these lectins differ in amino acid composition and hemagglutination properties.     

Utilisation of soil organic P by agroforestry and crop species in the field,western Kenya

A field experiment in western Kenya assessed whether the agroforestry species Tithonia diversifolia (Hemsley) A. Gray, Tephrosia vogelii Hook f., Crotalaria grahamiana Wight & Arn. and Sesbania sesban (L) Merill. had access to forms of soil P unavailable to maize, and the consequences of this for sustainable management of biomass transfer. The species were grown in rows at high planting density to ensure the soil under rows was thoroughly permeated by roots. Soil samples taken from beneath rows were compared to controls, which included a bulk soil monolith enclosed by iron sheets within the tithonia plot, continuous maize, and bare fallow plots. Three separate plant biomass samples and soil samples were taken at 6-month intervals, over a period of 18 months. The agroforestry species produced mainly leaf biomass in the first 6 months but stem growth dominated thereafter. Consequently, litterfall was greatest early in the experiment (0–6 months) and declined with continued growth. Soil pH increased by up to 1 unit (from pH 4.85) and available P increased by up to 38% (1 g P g^–1) in agroforestry plots where biomass was conserved on the field. In contrast, in plots where biomass was removed, P availability decreased by up to 15%. Coincident with the declines in litterfall, pH decreased by up to 0.26 pH units, plant available P decreased by between 0.27 and 0.72 g g^–1 and P_o concentration decreased by between 8 and 35 g g^–1 in the agroforestry plots. Declines in P_o were related to phosphatase activity (R²=0.65, P<0.05), which was greater under agroforestry species (0.40–0.50 nmol MUB s^–1 g^–1) than maize (0.28 nmol MUB s^–1 g^–1) or the bare fallow (0.25 nmol MUB s^–1 g^–1). Management of tithonia for biomass transfer, decreased available soil P by 0.70 g g^–1 and P_o by 22.82 g g^–1. In this study, tithonia acquired P_o that was unavailable to maize. However, it is apparent that continuous cutting and removal of biomass would lead to rapid depletion of P stored in organic forms.     

人血小板生成素全长分子在酵母系统中的分泌表达及活性分析

外源基因可通过整合型载体被整合到毕赤酵母（Ｐｉｃｈｉａｐａｓｔｏｒｉｓ）染色体上,获得遗传性稳定分泌表达株．利用酵母信号肽ＭＦα,对该信号肽蛋白酶识别位点的相关序列进行重新设计,使天然人ＴＰＯ成熟肽在毕赤酵母系统中分泌表达成功．表达产物经Ｗｅｓｔｅｒｎ－ｂｌｏｔ进行分析,分子量约为６６ｋＤ处蛋白条带可被ＴＰＯ抗体识别;表达量约为０．１ｇ／Ｌ;Ｎ端氨基酸序列分析结果与设计的一致;表达产物对小鼠骨髓细胞形成巨核细胞集落形成单位（ｍｅｇａｋａｒｙ－ｏｃｙｔｅｃｏｌｏｎｙｆｏｒｍｉｎｇｕｎｉｔ,ＣＦＵ－Ｍｅｇ）具有明显的刺激作用．     

人肝金属硫蛋白-I_A基因在鱼腥藻中的克隆与表达

将人工合成的人肝金属硫蛋白（ｍｅｔａｌｏｔｈｉｏｎｅｉｎ,简称ＭＴ）－ＩＡ基因插入至中间载体ｐＲＬ－４３９上强启动子ｐｓｂＡ后,再将其与穿梭载体ｐＫＴ－２１０相连,得到大肠杆菌－蓝藻穿梭表达载体ｐＫＴ－ＭＴ,用三亲接合转移法将ｐＫＴ－ＭＴ转入丝状体蓝藻－鱼腥藻７１２０,经链霉素筛选,得到了稳定的转人肝ＭＴ－ＩＡ基因鱼腥藻．纯化单藻落,液体扩大培养．从鱼腥藻中提取的质粒经Ｓｏｕｔｈｅｒｎ印迹分析,确定人肝ＭＴ－ＩＡ基因已转入鱼腥藻７１２０中,Ｗｅｓｔｅｒｎ印迹分析表明,金属硫蛋白在转人肝ＭＴ－ＩＡ基因鱼腥藻中得到了表达．经原子吸收光谱法测定表达量约为７００μｇＭＴ／ｇ鲜藻,重金属耐受性实验表明,得到了能耐受重金属－镉的转人肝ＭＴ－ＩＡ基因鱼腥藻,它将在清除水域中重金属污染和医药研究方面发挥重要作用．     

Penetration of Crotalaria juncea,Dolichos lablab,and Sesamum indicum Roots by Meloidogyne javanica

Penetration of Crotalaria juncea (PI 207657 and cv. Tropic Sun) Dolichos lablab cv. Highworth, and Sesamum indicum by juveniles (J2) of Meloidogyne javanica was assessed to investigate the mechanism by which these plants may reduce nematode numbers in the field. Growth chamber experiments were conducted at 25 C, with vials containing 90 g sand infested with 450 J2; tomato (UC 204 C) was included as a susceptible host. Fifteen days after inoculation, roots were stained and the nematodes within stained roots were counted. Both C. juncea lines were highly resistant to penetration, as they contained significantly fewer nematodes per cm of root and per root system than the other plants. Although containing more nematodes per cm of root than C. juncea, S. indicum and D. lablab had significantly fewer nematodes per root system and per cm of root than tomato. Roots were significantly longer in the plants with the lowest nematode penetration. Although C. juncea, D. lablab, and S. indicum may have potential utility as cover or rotation crops in soil infested with M. javanica, further quantitative information on the reproduction of M. javanica and other nematodes in these plants is needed.     

High-resolution time series of vessel density in Kenyan mangrove trees reveal a link with climate

Tropical trees are often excluded from dendrochronological investigations because of a lack of distinct growth ring boundaries, causing a gap in paleoclimate reconstructions from tropical regions. The potential use of time series of vessel features (density, diameter, surface area and hydraulic conductivity) combined with spectral analysis as a proxy for environmental conditions in the mangrove Rhizophora mucronata was investigated. Intra-annual differences in the vessel features revealed a trade-off between hydraulic efficiency (large vessels) during the rainy season and hydraulic safety (small, more numerous vessels) during the dry season. In addition to the earlywood-latewood variations, a semiannual signal was discovered in the vessel density and diameters after Fourier transformation. The similarity in the Fourier spectra of the vessel features and the climate data, in particular mean relative humidity and precipitation, provides strong evidence for a climatic driving force for the intra-annual variability of the vessel features. The high-resolution approach used in this study, in combination with spectral analysis, may have great potential for the study of climate variability in tropical regions.     

Ultrastructural Study of Secondary Wall Formation in the Stem Fiber of Phyllostachys pubescens

Ultrastructural changes in secondary wall formation of Phyllostachys pubescens Mazel fiber were investigated with transmission electron microscopy. Fiber developed initially with the elongation of cells containing ribosomes, mitochondria and Golgi bodies in the dense cytoplasm. During the wall thickening, the number of rough endoplasmic reticulum and Golgi bodies increased apparently. There were two kinds of Golgi vesicles, together with the ones from endoplasmic reticulum formed transport vesicles. Many microtubules were arranged parallel to the long axis of the cell adjacent to the plasmalemma. Along with the further development of fiber, polylamellate structure of the secondary wall appeared, with concurrent agglutination of chromatin in the nucleus, swelling and disintegration of organelles, while cortical microtubules were still arranged neatly against the inner side of plasmalemma. Lomasomes could be observed between the wall and plasmalemma. The results indicated that the organelles, such as Golgi bodies together with small vesicles, rough endoplasmic reticulum and lomasomes, played the key role in the thickening and lignification of the secondary wall of bamboo fiber, though cortical microtubules were correlative with the process as well.