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1. chinaXiv:201905.00051 [pdf]

谷氨酸棒状杆菌异源合成萜类化合物的研究进展

徐硕; 卢文玉
Subjects: Biology >> Bioengineering

萜类化合物具有可观的商业价值,但生产过程复杂,产量低,利用微生物异源合成萜类化合物已成为热点。谷氨酸棒状杆菌内含合成萜类色素的途径,具有异源合成萜类化合物的天然优势和研究前景。首次对谷氨酸棒状杆菌合成萜类化合物进行了综述,从萜类合成途径、关键酶和全局调控机制三个方面进行了途经介绍。概述了谷氨酸棒状杆菌中单萜、倍半萜、四萜类化合物的异源合成,并对利用谷氨酸棒状杆菌高效合成萜类化合物所需解决的问题进行讨论,为谷氨酸棒状杆菌高效合成萜类化合物提供建议。

submitted time 2019-05-06 Hits1331Downloads9 Comment 0

2. chinaXiv:201904.00094 [pdf]

6-羟基烟酸3-单加氧酶(NicC)催化反应机理研究

王菲; 胡春辉; 于浩
Subjects: Biology >> Bioengineering

恶臭假单胞菌(Pseudomonas putida)KT2440中的6-羟基烟酸(6HNA)3-单加氧酶(NicC)是烟酸代谢过程中的关键酶。NicC通过在吡啶环上加羟基对吡啶环进行了活化,从而使得吡啶环可在双加氧酶催化下开环最终被完全降解。本研究通过去除NicC的N端稀有密码子增加了NicC的表达量,进一步利用Ni-Sepharose重力柱对NicC进行了纯化。通过实验发现,NicC的最适反应温度为30℃-40℃,最适反应pH为8.0。Cd2+离子对于NicC的酶活有明显的抑制作用。当NADH的浓度为0.25 mM的时候,底物6HNA所对应的NicC的最大酶活为14.1 U/mg,Km值为51.8 μM;当6HNA的浓度为0.25 mM的时候,底物NADH所对应的NicC的最大酶活为10.79 U/mg,Km值为15.0 μM。通过HPLC和LC-MS分析表明,NicC可以在NADH和氧气的参与下催化6HNA转化生成2,5-二羟基吡啶(2,5-DHP)和甲酸,另外可以将对羟基苯甲酸转化生成对苯二酚。同位素标记实验表明产物2,5-DHP中的氧原子来源于参与反应的氧气。该研究为研究吡啶类化合物微生物代谢提供了理论基础。

submitted time 2019-04-21 From cooperative journals:《中国生物工程杂志》 Hits1232Downloads49 Comment 0

3. chinaXiv:201904.00073 [pdf]

阻止文化驱动的入侵生物扩散

李雄; Supriyo Basak; 周睿; 张卫哲; 付瑶; 周新茂; 施超; 郗厚诚; 杨永平
Subjects: Biology >> Ecology

地区文化(如宗教、饮食或旅游文化)有时会驱动入侵生物的扩散,我们必须采取措施来阻止入侵生物融入大众文化。

submitted time 2019-03-30 Hits1434Downloads81 Comment 0

4. chinaXiv:201903.00232 [pdf]

Conversion of cropland into agroforestry land versus naturally-restored grassland alters soil macro-faunal diversity and trophic structure in the semi-arid agro-pasture zone of northern China

LIU Rentao
Subjects: Biology >> Ecology

Restoration of cropland (termed 'Farm') after abandonment including shrubs (termed 'Shrub'), trees (termed 'Tree') and natural grassland (termed 'Grass') has become a routine process aimed to improve land productivity and control desertification. During this restoration process, soil macro-faunal diversity, and trophic structure were investigated at four types of sites (Farm, Shrub, Tree, and Grass) during growing season in the semi-arid agro-pasture zone of northern China. Results indicated that the Staphylinidae family was found to dominate at the Grass, Shrub, and Tree sites, whiles larval Pyralidae individuals were found at the Grass site only. The density of the omnivores (i.e., Formicidae family) was significantly (P<0.05) greater at the Grass site than at the Tree and Farm sites. The total density and richness of predator and phytophages were found to be markedly (P<0.05) greater at the Grass site than at the Farm site. Meanwhile, we found the taxon richness of predators was significantly (P<0.05) higher at the Shrub site than at the Farm and Tree sites. Compared with the Farm and afforested Shrub/Tree sites, the Grass site had greater density, taxon richness, and Shannon index (P<0.05). In conclusion, natural restoration of abandoned croplands toward grassland was an effective strategy relative to artificial afforestation for improvement of soil biological diversity. Moreover, planting shrub is a preferable measure in abandoned croplands for land development in the semi-arid agro-pasture zone of northern China.

submitted time 2019-03-28 From cooperative journals:《Journal of Arid Land》 Hits3890Downloads2304 Comment 0

5. chinaXiv:201903.00233 [pdf]

Exogenously applied glycinebetaine induced alteration in some key physio-biochemical attributes and plant anatomical features in water stressed oat (Avena sativa L.) plants

Anum SHEHZADI
Subjects: Biology >> Physiology

Although exogenous application of glycinebetaine (GB) is widely reported to regulate a myriad of physio-biochemical attributes in plants under stressful environments including drought stress, there is little information available in the literature on how and up to what extent GB can induce changes in anatomical features in water starved plants. Thus, the present research work was conducted to assess the GB-induced changes in growth, physio-biochemical, and anatomical characteristics in two cultivars (CK-1 and F-411) of oat (Avena sativa L.) under limited water supply. After exposure to water stress, a considerable reduction was observed in plant growth in terms of lengths and weights of shoot and roots, leaf mesophyll thickness, leaf midrib thickness, root cortex thickness, root diameter, stem diameter, stem phloem area, and stem vascular bundle area in both oat cultivars. However, water stress resulted in a significant increase in leaf total phenolics, hydrogen peroxide (H2O2), ascorbic acid (AsA), GB contents, activities of enzymes (CAT, SOD and POD), total soluble proteins, leaf epidermis (abaxial and adaxial) thickness, bulliform cell area, sclerenchyma thickness, root endodermis and epidermis thickness, root metaxylem area, stem metaxylem area and stem sclerenchyma thickness in both oat cultivars. Foliar-applied 100 mM GB suppressed H2O2 contents, while improved growth attributes, free proline and GB contents, activity of SOD enzyme, leaf abaxial epidermis thickness, leaf bulliform cell area, leaf midrib thickness, leaf sclerenchyma thickness, root cortex thickness, root endodermis, epidermis thickness, root stele diameter, stem diameter, stem epidermis thickness, stem metaxylem area, and stem phloem and vascular bundle area in both oat cultivars. For both oat cultivars, CK-1 was superior to F-411 in leaf abaxial epidermis thickness, leaf mesophyll, leaf sclerenchyma, root metaxylem area, stem diameter, stem epidermis, sclerenchyma thickness, stem metaxylem area, and stem vascular bundle area. Overall, both oat cultivars showed inconsistent behavior to water stress and foliar-applied GB in terms of different physio-biochemical attributes, however, CK-1 was superior to F-411 in a number of anatomical features of leaf, root, and stem.

submitted time 2019-03-28 From cooperative journals:《Journal of Arid Land》 Hits1174Downloads134 Comment 0

6. chinaXiv:201903.00235 [pdf]

Impact of air drought on photosynthesis efficiency of the Siberian crabapple (Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia, Russia

Alexandr RUDIKOVSKII
Subjects: Biology >> Botany

The adaption of photosynthesis, being a key metabolic process, plays an important role in plant resistance to air drought. In this study, the Siberian crabapple (Malus baccata L. Borkh.) in the forest-steppe zone of Transbaikalia region, Russia, was subjected to air drought stress and its photosynthesis characteristics were analyzed. The results show that air drought and sufficient soil moisture supply lead to the decrease in the total chlorophyll (Chl) content, while the ratio of Chls to carotenoids is constant in the Siberian crabapple tree. The function of photosystem II (PS-II) in the crabapple trees is characterized by a decrease in the fraction of absorbed light energy spent on the photochemical work and an increase in the proportion of non-photosynthetic thermal quenching. These changes indicate the photosynthetic down-regulation that acts as a universal photoprotective mechanism. During the midday hours, the combination of high air temperature and low air humidity leads to the decrease in the maximum photochemical quantum yield of photosystem II (Fv/Fm) and the efficiency of photosynthesis (PABS). The parameters of leaf gas exchange show the significant differences in these values between the control and experimental variants. During the morning hours, the Siberian crabapple, growing in the Irkutsk City, assimilates carbon dioxide more intensively. Due to the higher air humidity, the stomata are kept open and the necessary amount of carbon dioxide entries the sites of carboxylation. The low air humidity combined with wind in the experimental variants leads to the unreasonably high water loss in the crabapple leaves by more than 27% as compared to the control variant (Irkutsk City). However, water use efficiency in the morning hours increases during plant photosynthetic processes, i.e., 42% higher than that of control. This, apparently, is a reflection of the adaptation processes of the Siberian crabapple to the air drought and parching wind.

submitted time 2019-03-28 From cooperative journals:《Journal of Arid Land》 Hits1141Downloads148 Comment 0

7. chinaXiv:201903.00192 [pdf]

持续激活型CIPK9 在花粉管生长过程中的生物学功能及亚细胞定位分析

周利明; 房玮
Subjects: Biology >> Botany >> Applied botany

植物的花粉管生长是一个多因素参与的生理学过程,需要多种信号传导系统来引导植物细胞完成。钙离子作为第二信使,可以通过钙传感器CBLs 激活下游的蛋白激酶CIPKs而参与调控细胞的极性发育过程。该研究中CIPK9 被确定为候选基因,其C 端与绿色荧光蛋白(GFP)相融合,通过基因枪技术在烟草花粉中进行瞬时表达,观察对应的亚细胞定位及花粉管中诱导的表型。结果显示GFP 标记的CIPK9 定位于花粉管中高速运动的颗粒状细胞器,并可随胞质环流进行规律的运动。为进一步探究CIPK9 的生物学功能,该研究构建了持续激活型CIPK9(CACIPK9)。与全长CIPK9 相比较,CACIPK9 缺少C 末端的调控区域,并在激酶区域的激活环中进行了点突变,从而表现出不受调控的持续高活性。实验结果显示缺少C 端调控区的CACIPK9 表现出非特异性的亚细胞定位,即与GFP 对照相同的胞内弥散定位,说明CIPK9 的C 末端调控区对于其在花粉管中的正确定位发挥重要的调控作用。另外,CACIPK9 过表达可以引起花粉管的去极化生长表型。综上所述,CIPK9 作为钙信号下游家族的一员参与了花粉管极性生长的相关过程,并对花粉管的生长具有一定的调控作用。

submitted time 2019-03-14 From cooperative journals:《广西植物》 Hits2969Downloads218 Comment 0

8. chinaXiv:201903.00196 [pdf]

马尾松细胞分裂素羟化酶基因PmCYP735A 克隆与表达分析

徐梦璇; 吴玲; 类彦东; 徐立安; 胥猛
Subjects: Biology >> Botany >> Applied botany

细胞分裂素是一类促进细胞分裂与分化的腺嘌呤衍生物,广泛参与植物器官形态建成及胁迫响应。细胞分裂素羟化酶CYP735A 属于细胞色素P450 单加氧酶家族成员,它通过羟基化作用调控植物体内异戊烯基腺嘌呤与反式玉米素的含量水平, 在植物生长发育过程中发挥重要作用。在林木树种中鲜有细胞分裂素羟化酶基因克隆和鉴定的相关报道,该文首次在针叶树种马尾松(Pinus massoniana Lamb.)中采用cDNA 末端快速克隆(RACE)技术克隆并鉴定出1 个CYP735A基因。马尾松CYP735A 基因(PmCYP735A)cDNA 全长为1 744 bp,包括1 647 bp 的开放阅读框,44 bp 的5’端非翻译区和53 bp 的3’端非翻译区。该基因编码蛋白由548 个氨基酸残基组成,其二级结构含有丰富的α-螺旋和无规则卷曲。该基因编码蛋白不含跨膜区域,且无信号肽酶切位点,在第399-406 和475-484 个氨基酸残基存在P450 超家族保守特征序列ETLRLYP(ExxRxxP)和血红素结合区域(Heme-binding region)FSFGPRKCVG(FxxGxRxCxG)。系统进化树分析表明,马尾松PmCYP735A 与水稻、玉米、拟南芥CYP735A 蛋白归属于同一小的进化枝,而可可、毛果杨、麻风树和橡胶树等的CYP735A 同源蛋白相对集中的定位于另一进化分支。实时定量PCR检测发现,PmCYP735A 基因在马尾松根和茎中的表达量显著高于叶,该基因响应外源生长素NAA诱导表达,随着诱导时间呈现出先上升再下降的表达趋势。该研究结果有助于深入探究CYP735A基因家族的生物学功能及其在物种间的表达调控异同,为进一步挖掘马尾松优异基因资源奠定基础。

submitted time 2019-03-14 From cooperative journals:《广西植物》 Hits3367Downloads366 Comment 0

9. chinaXiv:201903.00193 [pdf]

中国橙衣属和果衣属地衣的新记录种

王春晓; 孙美洁; 赵遵田
Subjects: Biology >> Botany >> Applied botany

通过对采自云南省景东彝族自治县无量山地衣标本的研究,发现了橙衣属的一个中国新纪录Caloplaca indica(三室类型孢子)和果衣属的一个中国新纪录Ramboldia haematites。在对实验室标本的整理过程中,发现Ramboldia haematites 在福建省和广西省同样存在。该文详细描述了其形态学、解剖学和化学方面的特征,并且提供了显微结构照片。本研究丰富了云南省、福建省和广西省地衣的物种多样性,为橙衣属和果衣属地衣分类学研究提供基础数据和可靠资料。所用标本存放在山东师范大学植物标本室(SDNU)。

submitted time 2019-03-14 From cooperative journals:《广西植物》 Hits3107Downloads125 Comment 0

10. chinaXiv:201903.00198 [pdf]

土壤镉胁迫对田七体内镉分布及富集特性影响

李素霞; 陈玉萍; 韦司棋; 林俊良; 何晓诗; 农叶弯; 齐媛; 覃莉晨
Subjects: Biology >> Botany >> Applied botany

田七( Panax notoginseng (Burk.) F. H. Chen)是我国一种传统珍贵草本药用植物,其重金属污染问题已引起广泛关注,相关研究表明一定浓度的镉对田七生长会产生抑制,镉胁迫会降低田七主要药效成分皂苷的积累,影响田七药材质量。田七中镉的健康风险评价后认为其危害商数( HQ) 大于1,说明田七药材中的镉对服用者有非致癌风险。为了揭示田七不同部位对镉毒害的响应,明确不同浓度镉污染对田七体内镉分布的基本特征以及不同部位的富集特性,揭示镉胁迫对田七不同部位的影响机制及富集转移特性。在“田七之乡”广西靖西市田七园以三年生田七为试验材料,土培条件下,以不施镉处理为空白对照,设置6个镉浓度梯度(5、10、20、30、40、50 mg·kg-1),分析了在不同浓度镉胁迫下田七不同部位镉积累特征以及转移特性。研究表明:在不同器官(叶、茎、剪口、须根、主根)随着镉浓度的增加各器官镉的积累量均显著(P < 0.05)增加,呈正相关关系。田七不同部位镉含量的分布特征表现为:空白对照下田七各器官镉累积分布为:须根>剪口>主根>茎>叶,当镉浓度为5、10、20、30、40、50 mg·kg-1 时,田七镉分布表现为:剪口>主根>须根>茎>叶;地下部镉含量显著高于地上部镉含量,随着镉浓度的增加,无论地下部生物富集系数还是地上部生物富集系数均成逐渐降低的趋势。

submitted time 2019-03-14 From cooperative journals:《广西植物》 Hits2950Downloads130 Comment 0

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