Wheat germ agglutinin (WGA) gene expression and ABA accumulation in the developing embryos of wheat (Triticum aestivum) in response to drought

Expression of wheat germ agglutinin (WGA) gene inthe developing embryos of wheat (Triticumaestivum L. cv. C-306) was studied in relation toabscisic acid (ABA) accumulation under water stressconditions. Imposition of water stress resulted inelevated ABA levels in the embryos at threedevelopmental stages (18, 24 and 30 DPA). On thecontrary, the effect of drought stress on WGAaccumulation was stage dependent with significantincrease in WGA content being observed at only 24 DPA. Our results suggest that apart from ABA, otherfactors which are temporally expressed, are alsoinvolved in regulation of WGA gene expression.     

Episodic seedling growth in Allosyncarpia ternata,a lignotuberous,monsoon rainforest tree in northern Australia

On the western Arnhem Land Plateau, Northern Territory, Australia, seedlings of the canopy tree Allosyncarpia ternata S.T. Blake typically spend many years (perhaps decades) as small (<1 m), multistemmed plants on the forest floor. In this establishment phase, long periods of apparent inactivity are interrupted by episodes of rapid growth. This paper describes a 5‐year field‐monitoring program to examine the pattern of seedling growth and survival in allosyncarpia forest, and field and shadehouse measurements of lignotuber size. Individual seedlings may produce, each wet season, a number of fast‐growing stems, which then die back in the following dry season. As a result, mean annual above‐ground growth during this life stage is negligible. With each wet season, however, the seedling extends its below ground parts – a large lignotuber and a deep root system. After a number of years, when the lignotuber has grown large enough to sustain massive shoot growth, when a suitable light gap becomes available, and presumably when roots reach reliable dry‐season water supplies, the seedling grows rapidly. Thus, the shortage of saplings in allosyncarpia forest is due to the short time that individual plants spend at that particular growth‐stage, rather than to any dysfunction in recruitment.     

The development of the region between the preexisting and nascent membranes during the first cleavage of Rana amurensis eggs

The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, branched and randomly distributed protrusionswhich are derived largely from the preexistingmembrane,and a lower part,a band with microvilli.During 4-and 8-cel1 stages,the strip is almost vanishedand microvilli in the band is shortened.The nascentmembrane is smooth at the 180°stage,then a rough areaappears below the smooth region and quickly expands.Wheat germ agglutinin which can bind to preexistingmembrane interrupts the development of the regionbetween the preexisting and nascent membranes.Detergent,Brij,having the property to increase the areaof nascent membrane,does not interrupt the developmentof the region between the preexisting and nascentmembranes.     

E. coli sabotages the in vivo production of O-linked β-N-acetylglucosamine-modified proteins

The O-linked β-N-acetylglucosamine (O-GlcNAc) post-translational modification is an important, regulatory modification of cytosolic and nuclear enzymes. To date, no 3-dimensional structures of O-GlcNAc-modified proteins exist due to difficulties in producing sufficient quantities with either in vitro or in vivo techniques. Recombinant co-expression of substrate protein and O-GlcNAc transferase in Escherichia coli was used to produce O-GlcNAc-modified domains of human cAMP responsive element-binding protein (CREB1) and Abelson tyrosine-kinase 2 (ABL2). Recombinant expression in E. coli is an advantageous approach, but only small quantities of insoluble O-GlcNAc-modified protein were produced. Adding β-N-acetylglucosaminidase inhibitor, O-(2-acetamido-2-dexoy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), to the culture media provided the first evidence that an E. coli enzyme cleaves O-GlcNAc from proteins in vivo. With the inhibitor present, the yields of O-GlcNAc-modified protein increased. The E. coli β-N-acetylglucosaminidase was isolated and shown to cleave O-GlcNAc from a synthetic O-GlcNAc-peptide in vitro. The identity of the interfering β-N-acetylglucosaminidase was confirmed by testing a nagZ knockout strain. In E. coli, NagZ natively cleaves the GlcNAc-β1,4-N-acetylmuramic acid linkage to recycle peptidoglycan in the cytoplasm and cleaves the GlcNAc-β-O-linkage of foreign O-GlcNAc-modified proteins in vivo, sabotaging the recombinant co-expression system.     

Magnetic beads-assisted mild enrichment procedure for weak-binding lectins

Investigating unidentified weak-acting lectins is important for understanding glycan-related phenomena. We have developed an improved screening method for weak-acting lectins using glycan-conjugated magnetic beads (or glycobeads) involving a partial washing method and named it the mild enrichment procedure. Weak-acting lectins exist in equilibrium between bound lectin and free lectin produced by dissociation, whereas most tight-binding lectin exists in a bound state. The conventional washing step, in which the solution phase is replaced, may remove dissociated lectin from around the glycobeads; therefore, we attempted to leave a buffer space around the glycobeads to maintain the association–dissociation equilibrium of weak-acting lectins. Our results revealed that our mild enrichment procedure for screening for weak interactions, such as maltose–concanavalin A (K_a ∼ 10⁴ M⁻¹) and lactose–peanut agglutinin (K_a ∼ 10³ M⁻¹) interactions, was more effective than conventional batch methods.     

High mannose-specific lectin (KAA-2) from the red alga Kappaphycus alvarezii potently inhibits influenza virus infection in a strain-independent manner

The carbohydrate binding profile of the red algal lectin KAA-2 from Kappaphycus alvarezii was evaluated by a centrifugal ultrafiltration–HPLC method using pyridylaminated oligosaccharides. KAA-2 bound exclusively to high mannose type N-glycans, but not to other glycans such as complex type, hybrid type, or the pentasaccharide core of N-glycans. This lectin exhibited a preference for an exposed α1–3 Man on a D2 arm in a similar manner to Eucheuma serra agglutinin (ESA-2), which shows various biological activities, such as anti-HIV and anti-carcinogenic activity. We tested the anti-influenza virus activity of KAA-2 against various strains including the recent pandemic H1N1-2009 influenza virus. KAA-2 inhibited infection of various influenza strains with EC₅₀s of low nanomolar levels. Immunofluorescence microscopy using an anti-influenza antibody demonstrated that the antiviral activity of KAA-2 was exerted by interference with virus entry into host cells. This mechanism was further confirmed by the evidence of direct binding of KAA-2 to a viral envelope protein, hemagglutinin (HA), using an ELISA assay. These results indicate that this lectin would be useful as a novel antiviral reagent for the prevention of infection.     

Effects of purified soybean agglutinin on growth and immune function in rats

Abstract

The objective of this study was to investigate the effect of purified soybean agglutinin on growth and immune function in rats. Thirty male Sprague-Dawley rats (77.8 ± 2.6 g) were individually fed casein-cornstarch based diets containing 0, 0.05, 0.10, 0.15 or 0.20% soybean agglutinin (w/w) during a 20-day experiment. Growth declined linearly with increasing the concentration of soybean agglutinin (p < 0.05). The proliferation of lymphocytes in spleen, lymph nodes and blood decreased with an increase in dietary soybean agglutinin (p < 0.05). The concentrations of interleukin-2, interferon-γ and tumor necrosis factor- in plasma, spleen, and mesenteric lymph nodes as well as plasma concentrations of IgA, IgG and IgM also declined with increasing dose of soybean agglutinin (p < 0.05). The results show that dietary soybean agglutinin has negative effects on growth as well as both cell-mediated and humoral immune function of rats and appears to function in a dose-dependent manner.     

腐植酸对高温胁迫下掌叶半夏生长生理特性及块茎次生代谢的影响

采用不同浓度(0、20、40、60、80、100mg/L)腐植酸(HA)叶面喷施处理,通过盆栽实验分析了HA对高温胁迫下掌叶半夏幼苗生长生理指标及次生代谢的调控效应。结果显示:(1)各浓度HA处理均可不同程度地促进高温胁迫下掌叶半夏的生长发育,且以80mg/L HA处理下其块茎鲜重(6.990 5g/株)、叶柄鲜重(1.755 4g/株)及总叶绿素含量(19.961 3mg/g)最高,较对照分别显著提高21.25%、118.5%和37.19%。(2)当HA处理浓度为60mg/L时,掌叶半夏幼苗叶片中可溶性糖、可溶性蛋白含量均最高,分别比对照显著提高66.67%、40.91%;叶片抗氧化酶(SOD、POD)活性达到最大值,MDA含量降至最低,SOD、POD活性分别比对照显著提高818.98%和48.2%,MDA含量较对照显著降低62.08%;且块茎中鸟苷含量较高,比对照显著提高52.94%。(3)当叶面喷施80mg/L HA时,掌叶半夏幼苗叶片中游离脯氨酸含量和块茎中总生物碱、总有机酸、腺苷的含量均最高,分别比对照显著提高169.63%、27.19%、42.32%、96.23%。研究表明,适宜浓度HA处理可显著提高高温胁迫下掌叶半夏幼苗叶片内抗氧化酶(SOD、POD)的活性及渗透调节物质(可溶性糖、可溶性蛋白、游离脯氨酸)含量,以及块茎中次生代谢产物(总生物碱、总有机酸、鸟苷和腺苷)的含量,有效减轻夏季高温对掌叶半夏幼苗叶片的伤害、延缓衰老、提高其幼苗抗热性,促进生长、延长生长期。