不同温度、光照对曼陀罗黑斑病菌孢子萌发率的影响

从曼陀罗黑斑病叶片上分离得到的病原菌[Alternaria daturicola],对其生物学特性进行了研究。采用凹玻片法,通过不同温度和光照处理条件对曼陀罗黑斑病的链格孢菌的孢子萌发率进行研究。结果表明：该病原菌孢子萌发的温度范围为5℃~40℃,最适温度为25℃~30℃;光照对孢子萌发无明显的影响。     

Characterization and Role of Glucose-6-phosphate Dehydrogenase of Populus suaveolens in Induction of Freezing Resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTTred) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTTred, indicating that the purified enzyme probably presented in cytosol of P suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P.suaveolens cuttings were also studied. The results show that G6PDH is characterized by Km value of 360/amol.L^-1 for G6P and 16μmol.L^-1 for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol‘L i except for NADPH and NADH)to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgC12, CaC12 and KC1 (all 1.0 mmol.L^-1) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl2 (1.0 mmol.L-1) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LTs0) of P. suaveolens cuttings during freezing acclimation at -20℃ were investigated. The results reveal that freezing acclimation decreases LTs0 of cuttings, and increases the activity of cytosolic G6PDH compared with control ones,while 2 d of de-acclimation at 25 ~C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT50. Furthermore,the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings.     

Comparison of G6PDH Activity and LT50 Between P.tomentosa and P.suaveolens During Freezing Acclimation

The differences of glucose-6P dehydrogenase(G6PDH) activity and freezing resistance induced by freezing acclima-tion between cuttings of freezing-sensitive P.tomentosa and freezing-resistant P.suaveolens were compared for exploring the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation.After 5d of freezing acclimation at -3℃ ,the LT50 of P.tomentosa has deereased from -6.2℃ incontrol cuttings to -14.3℃ in freezing acclimated ones,and the increase of LT50 of P.tomentosa has decreased from -6.2℃ in control cutting to -14.3℃ in freezing acclimated ones,and the increase of G6PDH activity was observed in freezing acclimated cuttings as compared with control ones.Whereas,when P.suaveolens was freezing acclimated at -20℃ for 5d,the LT50 has decreased from -27.1℃ in control cuttings to -43.5℃ in freezing acclimated ones,and the activity of G6PDH increased considerably.In addition,the increase of LT50 and the decrease of G6PDH activity resulting from 2d of deacclimation at 25℃ were found in two kinds of freezing acclimated cuttings.It is concluded that the increase in the activity of G6PDH may associate with the inherited freezing resistance of species and the enhancemen of freezing resistance of cuttings,and may play an important role in the antifreeze process under freezing temperature,which would provide the basis for the study on the molecular mechanism of freezing resistance in P.suaveolens and the cloning of gene associated with freezing resistance.     

曼陀罗及其变种紫花曼陀罗的形态性状比较研究

对曼陀罗与其变种紫花曼陀罗的生长特性进行了比较观察,结果表明：曼陀罗花白色,叶柄较长,叶片较宽,叶边缘齿数较多,叶面积较大,单株结实少,花丝着生位置偏花冠下部,而紫花曼陀罗叶柄较短、叶宽度小,叶长宽比大,叶边缘锯齿数少,茎粗,单株结实数多,果大,花长,花丝着丝点位置在花冠较高位,且抗逆性整体优于曼陀罗,这些形态差异特征可以作为曼陀罗与紫花曼陀罗的辅助分类依据。     

低温胁迫响应的甜杨miR475靶基因的预测及表达

MicroRNAs（miRNAs）通过使靶mRNA降解或翻译参与生物体的转录后调控,并在植物对生物与非生物胁迫的应答过程中发挥重要作用。本研究基于相关数据库,利用生物信息学方法,通过搜索预测及实验验证得到甜杨（Populus suaveolens）低温响应miR475的12条潜在靶基因,并对其降解位点进行分析;同时,以低温（0℃）处理不同时间甜杨幼苗为试材,利用荧光定量PCR对miR475及其靶基因的表达谱进行检测分析,结果发现,随着低温诱导时间的延长,miR475表达量呈下调趋势,而其靶mRNA的表达量则呈现相反趋势,表明甜杨miR475可能以降解靶mRNA的方式在抵御低温中发挥作用。本文研究结果可为甜杨抗冻机制的后续深入研究提供科学依据。     

High Level Expression of Glucose-6-phosphate Dehydrogenase Gene PsG6PDH from Populus suaveolens in E. coli

In order to investigate the functions of the gene PsG6PDH and the mechanisms underlying freezing tolerance of Populus suaveolens, the recombinant expression vector pET-G (pET30a-G6PDH), which contained full encoding region of PsG6PDH gene, was established. The recombinant was identified by lawn-PCR and double enzyme digestion and then transformed into expression host XA90 and induced by isopropyl-a-D-thiogalactoside (IPTG) to express 100 kD polypeptide of G6PDH fusion protein. The results showed that the expressed amount of the fusion protein culminated after 1 mmol·L–1 IPTG treatment for 4 h and that pET-G product was predominately soluble and not extra-cellular secreting.     

白花曼陀罗提取液对春尺蠖等昆虫的活性测定

以乙醇 水(1∶1)作为溶剂,采用微波辅助提取、浸泡提取等方法,从白花曼陀罗种子中得到提取液,用此液对春尺蠖等昆虫进行了活性测定。结果表明,白花曼陀罗种子提取液对杨毛臀萤叶甲东方亚种成虫、春尺蠖和荨麻蛱蝶幼虫具有较强的拒食活性,对蚜虫具有较强的触杀活性。其中,白花曼陀罗种子微波辅助提取液的拒食活性和触杀活性很强,24 h的拒食率达到了81.48%以上,处理48 h后对蚜虫的触杀活性高达88.7%。同样的拒食活性物质对幼虫的拒食率要比成虫高。相同溶剂的微波辅助提取液和直接浸提液的活性比较说明,利用微波辅助提取有利于生物活性物质的溶出。     

High level expression of glucose-6-phosphate dehydrogenase gene <Emphasis Type="Italic">PsG6PDH</Emphasis> from <Emphasis Type="Italic">Populus suaveolens</Emphasis> in <Emphasis Type="Italic">E. coli</Emphasis>

In order to investigate the functions of the gene PsG6PDH and the mechanisms underlying freezing tolerance of Populus suaveolens, the recombinant expression vector pET-G (pET30a-G6PDH), which contained full encoding region of PsG6PDH gene, was established. The recombinant was identified by lawn-PCR and double enzyme digestion and then transformed into expression host XA90 and induced by isopropyl-â-D-thiogalactoside (IPTG) to express 100 kD polypeptide of G6PDH fusion protein. The results showed that the expressed amount of the fusion protein culminated after 1 mmol&#8226;L^–1 IPTG treatment for 4 h and that pET-G product was predominately soluble and not extra-cellular secreting.     

几种药用植物对家蚕的药杀效果研究

取当年生新鲜有毒植物白花曼陀罗、狼毒大戟和白屈菜,用沸水浸提法分别制成药液,采用涂抹、浸泡、添食几种方法对家蚕进行毒杀试验。结果表明,白花曼陀罗对家蚕无触杀作用,但麻醉作用明显;狼毒大戟对家蚕具有明显的触杀和胃杀作用;白屈菜对家蚕的毒性作用较小。     

The relationship between soil inoculum density and plant infection as a basis for a quantitative bioassay of Verticillium dahliae

Using potato, eggplant and thorn apple as test plants, the relationship between soil inoculum density and plant infection was studied as a basis for the development of a quantitative bioassay of Verticillium dahliae. A linear relationship was demonstrated (P < 0.05) between soil inoculum density and population density on roots for all three test plants and for soil inoculum density and population density in sap extracted from stems for eggplant. Correlation coefficients were higher with densities on or in roots (R² varying from 0.45 to 0.99) than with densities in stems (R² varying from 0.04 to 0.26). With eggplant, population densities on/in root and in sap extracted from stems were significantly correlated at 20 and 25°C with Pearson's correlation coefficients of 0.41 and 0.53, respectively. For potato, root colonization was higher at 15 than at 20°C, whereas the reverse applied to eggplant. Stems of potato were less colonized than stems of eggplant. The pathozone sensu Gilligan (1985) was calculated to be <300 µm, indicating that infection was caused by microsclerotia which were located close to the roots. To assess the density of V. dahliae in plant tissue pipetting infested plant sap on solidified ethanol agar medium without salts yielded higher densities than using pectate medium or mixing sap with molten agar. A bioassay for determining effects of (a)biotic factors on development of V. dahliae in the plant is recommended with eggplants as a test plant, grown in soil infested with 300 single, viable microsclerotia g^-1 soil at a matric potential of –6.2 kPa, and incubated at 20°C for 8 weeks.