D-泛解酸内酯水解酶的定向进化

易错PCR结合DNA改组方法向D-泛解酸内酯水解酶基因中引入突变,并构建突变体库。利用酶的催化特点和产物特性建立了基于平板初筛和高效液相复筛的两步法D-泛解酸内酯水解酶活性筛选系统。用该筛选系统以酶活力和pH稳定性为指标对突变体库进行筛选,最终获得一株酶活力高且在低pH条件下稳定性好的突变体Mut E-861。该突变体的酶活力是野生型酶的5.5倍。对突变体和野生型酶在pH 6.0和pH 5.0条件下的残余酶活进行对比,在这两种pH条件下,突变体酶的酶活残留分别为75%和50%,而野生型酶只能保持原来的40%和20%。通过软件对突变体Mut E-861酶基因和野生型酶基因进行分析对比,发现突变体Mut E-861酶基因发生了三处点突变,其中突变使两处氨基酸取代,另一处为沉默突变,未引起氨基酸的变化。     

细茎石斛的化学成分

从兰科植物细茎石斛(Dendrobiummoniliforme(L.)Sw.)中分得一个新的联苄类化合物(moniliformine),以及6个已知化合物(a-dihydropicrotoxinin、对羟基顺式肉桂酸三十烷基酯、反式阿魏酸二十八烷基酯、b-谷甾醇、胡萝卜苷和二十九烷烃),经光谱解析(UV、IR、MS、1H-NMR、13C-NMR、DEPT、HMQC和COLOC),新化合物的结构被确定为3,4-二羟基-5,4'-二甲氧基联苄(3,4-dihydroxy-5,4'-dimethoxybibenzyl)。a-dihydropicrotoxinin为首次从自然界分离得到。     

A New Stromatolitic Mat Builder Discovered from Late Precambrian in Northern China

Abundant and preserved chain algal microfossils have been discovered in cherty stromatolitic mats from the second member of Gaoyuzhuang Formation (about 1,500 Ma old), Ling-qiu county of Shanxi province, China. They are described as Veteronostocale moniliforme Xu et Gao sp. nov.. The small diametral trichomes resemble the Family Nostocaceae in possessing specilized cells resembling the classic heterocysts and akinetes. This paper gives emphasis to the following remark: (1) The Gaoyuzhuang stromatolitic mats were products of microbial (Veteronostocale moniliforme) activity and the plant Nostocaceae was one of the main stromatolitic builders as both modern and Precambrian stromatolite-forming microorganisms; (2) Based on the fact that the chain fossils are preserved perpendicularly to the laminations the rates of sedimentation and algal growth were probably equal and each small sedimentary rhythm could be completed in about one or two months; (3) According to the environment and habits of living Nostoc Precambrian hydrosphere might be of a fresh water type.     

圆柏大痣小蜂雌成虫触角、下颚须及产卵器感器超微结构观察

圆柏大痣小蜂Megastigmus sabinae Xu et He是危害祁连圆柏球果种仁的寡食性害虫,其幼虫在球果内蛀食胚乳,并随球果同步发育,致使种子成熟后有果无仁,严重影响祁连圆柏种子生产。观察和分析圆柏大痣小蜂雌成虫触角、下颚须及产卵器感受器形态特征,旨在为圆柏大痣小蜂进化和行为策略研究提供基础。运用扫描电镜技术对圆柏大痣小蜂雌成虫的触角、下颚须及产卵器上的感受器进行观察,并对各感受器的形态特征进行分析。圆柏大痣小蜂触角为膝状,由支角突、柄节、梗节、环节、索节(7节)和棒节(3节)共14亚节组成,触角总长1 797.56±24.29μm,表面有B?hm氏鬃毛、板形感受器、毛形感受器、刺形感受器、锥形乳头状感器5种感器;下颚须由5节组成,第1节粗长,其余4节较细,表面有毛形感受器、刺形感受器、锥形感受器和栓锥形感受器4种感器;外产卵器由产卵鞘和产卵针组成,有毛形感受器、栓锥形感受器、半球形感受器和腔锥形感受器,产卵鞘长3.17±0.22 mm,表面具2类毛形感器,产卵针长5.01±0.41 mm,产卵针从基部开始,分为3个产卵瓣,外侧端部具"八"字形缺刻及2个腔锥形感器。圆柏大痣小蜂雌成虫触角、下颚须、产卵器上的感受器类型多样,形态变化丰富。不同感受器类型间存在一定差异,是圆柏大痣小蜂为适应生存而进化产生的适应性形态,不同感器形态与圆柏大痣小蜂寄主选择、产卵及交配策略具有一定的内在联系。本文首次对圆柏大痣小蜂的触角、下颚须、产卵器的感受器形态进行研究报道,为理解圆柏大痣小蜂的形态特征、进化和行为策略研究提供理了理论依据。     

中国贵州忍冬属一新变种

报道了贵州省忍冬属1个新变种——心叶皱叶忍冬(Lonicera reticulata Champ.var.cordifolia W.B.Xu),该变种与原变种皱叶忍冬(Lonicera reticulata Champ.var.reticulata)的主要区别在于苞片长1~1.5cm,远长于萼筒,叶片卵形至心形,宽可达10cm,基部明显心形。作者指定了模式标本,并对新变种生境中的伴生物种进行了描述。     

浙北几种园林观赏植物白粉菌及其两个新种

本文列出几种浙江省未报道过的园林观赏植物白粉菌,其中包括两个新种,即寄生于云实科紫荆的紫荆白粉菌Erysiphe cercidis T.Xu sp.nov.以及寄生于八角枫科瓜木的八角枫钩丝壳Uncinula alangii T.xu sp.nov.。新种有汉文及拉丁文描述。     

我国樟科楠木属上锈菌新变种——紫楠锈菌

本文报道我国天目山锈菌的一个新变种,即紫楠锈菌[Kernella lauricola (Thirum.) Thirum. var. phoebae Ge et T. Xu var. nov.],由于其寄主,冬孢子柱长度,冬孢子壁色泽、厚度等与印度报道的木姜子锈菌[Kernella lauricola(Thirum)Thirum]显然不同,故建立为新变种,新变种有汉文和拉丁文描述。     

稻恶苗菌异核体三种核型核DNA的RAPD分析

利用RAPD技术,对稻恶苗菌TJ47-26异核体的紫、红、白三种核型(同核体)核DNA进行比较,用80种10bp长的随机引物进行DNA扩增,共检测了基因组中近400个位点,未发现三种核型的基因组间有明显差异,表明紫、红、白三种核型的DNA碱基序列高度相似。由此推测TJ47-26异核体的三种不同核型是来自同一个核的变异体。     

Effects of fumonisin B1 on growth and metabolism of larvae of the yellow mealworm, Tenebrio molitor

The chronic and acute toxicity of fumonisin B₁ (FB₁), a mycotoxin from Fusarium moniliforme, to the larvae of the yellow mealworm, Tenebrio molitor, was assessed. The toxin was administered via the diet or injected directly into the larvae. Young T. molitor larvae fed on a diet containing 450 µg FB₁ per g diet exhibited reduced growth performance but only after consuming the fumonisin-contaminated diet for several weeks. FB₁-contaminated diet also reduced the rate of carbon dioxide production, food consumption and protein metabolism. The concentrations of FB₁ in the diet did not increase mortality, even when tested at the highest dose of 450 µg FB₁ per g of diet. Injection of 25 ng FB₁ per larva decreased the CO₂ production, but became significant only 11 days after the injection and was reversible with time. A parallel analysis of the retention of FB₁ by the larvae indicated that about 40% of the ingested FB₁ was excreted in the faeces.     

Nitrogen repression of fumonisin B1 biosynthesis in Gibberella fujikuroi

Fumonisins are a group of structurally related mycotoxins produced by Gibberella fujikuroi. The fungus produced fumonisin B1 (FB1) as early as 18 hour in a defined medium containing 1.25 mM or 2.5 mM ammonium phosphate, whereas fumonisin B1 production was repressed for 75 hour and 125 hour when mycelia were resuspended in media containing ammonium phosphate at 10 mM or 20 mM, respectively. Although total fumonisin B1 production was greater in resuspension cultures grown in higher concentrations of ammonium phosphate, the accumulation was independent of the inoculum size and carbon/nitrogen ratio. The addition of ammonium phosphate to cracked corn cultures also repressed fumonisin B1 production by 97%, and persisted for at least three weeks. Thus, biosynthesis of fumonisin B1 is regulated by a mechanism involving nitrogen metabolite repression, suggesting that control strategies that target the regulatory elements of nitrogen metabolism may be effective at reducing the risk of fumonisin contamination in food.