膜下滴灌对水稻根系形态及生理性状的影响

为探明水稻在膜下滴灌灌溉方式下根系生长发生的变化,设置小区试验与传统淹灌进行对比,以粳稻品种“T-04”和“T-43”为材料,研究了膜下滴灌灌溉方式对水稻根系形态、根系氧化力和硝酸还原酶的影响.结果表明:土表下20 cm深度,膜下滴灌水稻的根系长度、表面积、体积和平均直径都高于传统淹灌,并且差异具有统计学意义.土表下40 cm,膜下滴灌对水稻根系形态影响不具有统计学意义;水稻根系氧化力都是呈先增大,后减小的趋势,水稻根系氧化力最大期因品种而异.分蘖期膜下滴灌对水稻根系氧化力的影响因品种而异,但在拔节孕穗期、齐穗期和乳熟期,膜下滴灌水稻根系氧化力高于传统淹灌,并且差异具有统计学意义,膜下滴灌水稻后期根系具有较强的抗衰老能力;膜下滴灌水稻根系硝酸还原酶活性高于传统淹灌,但在分蘖期和乳熟期的差异不具有统计学意义,在拔节孕穗期和齐穗期差异具有统计学意义.     

Identification of a 4-Deoxy-l-erythro-5-hexoseulose Uronic Acid Reductase,FlRed, in an Alginolytic Bacterium Flavobacterium sp. Strain UMI-01

In alginate-assimilating bacteria, alginate is depolymerized to unsaturated monosaccharide by the actions of endolytic and exolytic alginate lyases (EC 4.2.2.3 and EC 4.2.2.11). The monosaccharide is non-enzymatically converted to 4-deoxy-l-erythro-5-hexoseulose uronic acid (DEH), then reduced to 2-keto-3-deoxy-d-gluconate (KDG) by a specific reductase, and metabolized through the Entner–Doudoroff pathway. Recently, the NADPH-dependent reductase A1-R that belongs to short-chain dehydrogenases/reductases (SDR) superfamily was identified as the DEH-reductase in Sphingomonas sp. A1. We have subsequently noticed that an SDR-like enzyme gene, flred, occurred in the genome of an alginolytic bacterium Flavobacterium sp. strain UMI-01. In the present study, we report on the deduced amino-acid sequence of flred and DEH-reducing activity of recombinant FlRed. The deduced amino-acid sequence of flred comprised 254 residues and showed 34% amino-acid identities to that of A1-R from Sphingomonas sp. A1 and 80%–88% to those of SDR-like enzymes from several alginolytic bacteria. Common sequence motifs of SDR-superfamily enzymes, e.g., the catalytic tetrad Asn-Lys-Tyr-Ser and the cofactor-binding sequence Thr-Gly-x-x-x-Gly-x-Gly in Rossmann fold, were completely conserved in FlRed. On the other hand, an Arg residue that determined the NADPH-specificity of Sphingomonas A1-R was replaced by Glu in FlRed. Thus, we investigated cofactor-preference of FlRed using a recombinant enzyme. As a result, the recombinant FlRed (recFlRed) was found to show high specificity to NADH. recFlRed exhibited practically no activity toward variety of aldehyde, ketone, keto ester, keto acid and aldose substrates except for DEH. On the basis of these results, we conclude that FlRed is the NADH-dependent DEH-specific SDR of Flavobacterium sp. strain UMI-01.     

冷藏大黄鱼SSO希瓦氏菌致腐能力差异机制初探

为探讨特定腐败菌(SSO)希瓦氏菌(Shewanella)致腐能力的差异机制,采用生化和16S rDNA鉴定冷藏大黄鱼货架期终点的产H2S菌,在灭菌鱼汁和无菌鱼块筛选4株致腐差异的希瓦氏菌,扩增氧化三甲胺(TMAO)还原酶基因及分析其表达量,并预测其蛋白质的理化性质。结果显示,22株产H2S菌均为希瓦氏菌属,其中 S.baltica占54.5%,为S. putrefaciens占40.9%,S. hafniensis占4.5%。希瓦氏菌在灭菌鱼汁中致腐能力存在显著差异,其中S. balticaXH2和XH8的缺点评分和TVB-N最高,S. putrefaciensXH14和XH17菌最低。接种无菌鱼块的4株希瓦氏菌中XH2的样品在72h出现腐败气味,48h细菌高于107cfu/g,产生较高的TMA、TVB-N、尸胺和腐胺和,XH8菌次之,XH14和XH17菌最慢。四株希瓦氏菌都扩增出2490bp的torA基因,且torA基因的表达量与致腐能力密切相关,S.balticaXH2最高。预测的TorA蛋白中S.balticaXH2的分子量和不稳定指数最大,理论等电点和总平均疏水性最小。可见,S. baltica XH2为冷藏大黄鱼的SSO,其强致腐能力与torA基因高表达量和TorA蛋白理化性质有关。研究为阐明希瓦氏菌致腐机制奠定了良好的基础。     

草莓FaMDHAR和FaGR的克隆与表达分析

为了探讨草莓中单脱氢抗坏血酸还原酶（Monodehydroascorbate reductase,MDHAR）和谷胱甘肽还原酶（Glutathione reductase,GR）基因的功能,采用同源克隆的方法从‘丰香’草莓中克隆得到cDNA全长序列,并采用实时定量PCR方法对其在不同组织和不同发育阶段果实中的表达模式进行分析。结果表明：草莓MDHAR基因cDNA（FaMDHAR,GenBank登录号：KP025946）全长1 305 bp,编码434个氨基酸,分子量约为47 kD,含有保守的FAD结合结构域,定位于细胞质中。GR基因cDNA（FaGR,GenBank登录号：JQ339738）开放阅读框全长1 491 bp,编码496个氨基酸,分子量为53 kD,定位于细胞质中。FaMDHAR在各组织中均有表达,在成熟果实中表达量最高,叶和花次之,根中最低;在果实发育过程中FaMDHAR在绿果期有相对较高的表达,随后急剧增加,到白熟期最高,之后下降并维持在相对稳定水平。FaGR在叶和花中表达较高,在成熟果实中较低;在果实发育过程中,表达量从小绿期呈现增加趋势,至转红果期达最高,随后逐渐下降,在成熟果实中较低。果实发育过程中酶活性变化呈现出与各自基因表达量相似的变化规律。经过4 ℃低温处理24 h后的草莓叶片中,FaMDHAR相对表达量较对照显著增加,而FaGR无显著变化。草莓中FaMDHAR和FaGR表达存在时空差异,并对低温逆境响应存在差异。     

Overproduction of reactive oxygen species involved in the pathogenicity of Fusarium in potato tubers

Differences in virulence between Fusarium sulphureum and Fusarium sambucinum were compared. Changes in reactive oxygen species production and metabolism in inoculated slices of potato tubers were also compared. The result showed that Fusarium infection induced significant production of ROS, lipid peroxidation and loss of cell membrane integrity, but low activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX). Compared to F. sambucinum, F. sulphureum led larger lesion diameters on potato tubers and slices. It resulted in more superoxide anion ($O_2^{-}$) and earlier peak of hydrogen peroxide (H₂O₂), but lower activity of catalase (CAT) and APX, and accompanied with higher malondialdehyde (MDA) content and lower cell membrane integrity. These findings suggested that overproduction of ROS involved in the pathogenicity of Fusarium in potato tubers.     

古侧柏组织培养研究

以陕西省黄陵县轩辕庙院内千年树龄黄帝手植柏（古侧柏）嫩枝为外植体进行茎段组织培养试验研究。经过初代培养和继代增殖培养,研究了不同植物生长调节剂种类及浓度、活性炭在组培各阶段的作用,并测定不同年龄段侧柏组织培养前后的硝酸还原酶活性。结果表明:最适启动培养基为1/2MS+6-BA 0.2 mg/L+NAA 0.1 mg/L+椰乳100 mL/L,适宜的继代培养基为1/2或1/4MS+ 6-BA 0.4 mg/L+NAA 0.1 mg/L+椰乳100 mL/L;活性炭对增殖无显著作用;古侧柏组织培养后硝酸还原酶活性可达到幼嫩水平。     

Temporal shifts in diversity and quantity of nirS and nirK in a rice paddy field soil

Denitrification is an important part of the nitrogen cycle in the environment, and diverse bacteria, archaea, and fungi are known to have denitrifying ability. Rice paddy field soils have been known to have strong denitrifying activity, but the microbes responsible for denitrification in rice paddy field soils are not well known. Present study analyzed the diversity and quantity of the nitrite reductase genes (nirS and nirK) in a rice paddy field soil, sampled four times in one rice-growing season. Clone library analyses suggested that the denitrifier community composition varied over sampling time. Although many clones were distantly related to the known NirS or NirK, some clones were related to the NirS from Burkholderiales and Rhodocyclales bacteria, and some were related to the NirK from Rhizobiales bacteria. These denitrifiers may play an important role in denitrification in the rice paddy field soil. The quantitative PCR results showed that nirK was more abundant than nirS in all soil samples, but the nirK/nirS ratio decreased after water logging. These results suggest that both diversity and quantity changed over time in the rice paddy field soil, in response to the soil condition.     

马尾松肉桂酰辅酶A还原酶基因(CCR)克隆及分析

对马尾松肉桂酰辅酶A还原酶基因(CCR)进行扩增、克隆和测序(GenBank登录号:EU753854).应用MEGA4.0.2软件对不同树种CCR基因的核苷酸和氨基酸序列进行比对,结果表明:马尾松CCR基因的外显子和内含子数目与火炬松、杨树、银合欢、光皮桦、冈尼桉、柳桉、蓝桉的外显子和内含子数目相同,都有5个外显子和4个内含子.马尾松CCR基因编码区975 bp,编码324个氨基酸.马尾松外显子Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ分别为133,155,186,353,148 bp,而内含子Ⅰ,Ⅱ,Ⅲ,Ⅳ分别为1 450,216,737,941 bp.马尾松CCR外显子和内含子连接处序列除内含子Ⅱ/外显子Ⅲ出现CTPuCG/外显子Ⅲ,其余遵循外显子/GTPuAG/外显子组成规律.马尾松外显子Ⅱ,Ⅲ,Ⅳ核苷酸数目与桉属、杨属、桦木属和松属树种相同,但外显子Ⅰ和外显子Ⅴ不尽相同.比对的树种间在该基因编码区核苷酸序列和氨基酸序列上相对保守,也存在一定差异.马尾松与火炬松、光皮桦、银合欢、杨树、冈尼桉、柳桉、蓝桉各物种间编码区核苷酸序列相似性大小分别为99.2%,67.8%,68.0%,68.9%,69.5%,69.3%,69.9%,而相应的氨基酸序列间相似性大小分别为99.1%,73.5%,72.5%,74.4%,75.0%,74.4%,75.0%.马尾松与其他13个树种CCR序列构建的系统进化树表明:3个针叶树种形成1个独立分支,而且最早进化.     

亚硝酸还原酶高产菌株的筛选及发酵条件优化

通过紫外线对巨大芽孢杆菌MPF-906进行了诱变处理,提高了产酶能力,变异株Z85酶活达到28.76 U/mL。进一步对其发酵条件进行研究,优化了培养基和培养条件。优化的培养基为：葡萄糖1.5%,牛肉膏0.2%,硫酸铵0.1%,K₂HPO₄ 0.135%,KH₂PO₄ 0.07%,NaCl 0.1%;无机盐溶液10 mL/L（即MgSO₄·7H₂O 0.04%、MnSO₄·H₂O 0.001%、CaCl₂·2H₂O 0.002%）。发酵条件为：摇床转速160 rpm,接种量4%,初始pH 6.5,30 ℃发酵20 h。在此最优化条件下,亚硝酸还原酶的酶活达到45.94 U/mL。     

昆嵛山醛糖还原酶抑制剂原料植物资源调查

对昆嵛山醛糖还原酶抑制剂原料植物资源进行了调查。结果表明,醛糖还原酶抑制剂主要分布在该区菊科、豆科和葡萄科等植物中,其中以葡萄科和豆科含醛糖还原酶抑制剂的植物种类最多。