成熟香蕉果实活性氧与乙烯形成酶活性的关系

香蕉果实成熟过程,随着活性氧产生速率从低水平→迅速跃升→高峰→下降的变化,其乙烯形成酶活性及乙烯产生也经厅了基本同步的过程。显示了三者之间具有某种内在联系。外源超氧阴离子自由基能使乙烯形成酶活性及乙烯产生出现跃升和高峰的时间明显提前;超氧歧化酶则使ＥＦＥ活性及乙烯产率明显下降。进一步说明了在香蕉果实成熟过程中,Ｏ２可能是引起ＥＦＥ活性及乙烯产生迅速上升的原因之一,而过氧化氢则被证明与ＥＦＥ活性及乙     

苹果果实香气产生过程中氨基酸和脂肪酸含量及一些相关酶活性的变化

研究了苹果果实成熟期间香气和乙烯的产生动态,以及游离氨基酸、游离脂肪酸含量和脂氧合酶(LOX)、醇-酰基转移酶(AAT)活性的变化.结果表明,果实香气物质是随着乙烯释放的增加而产生和增加的.在此过程中,异亮氨酸大量积累.游离脂肪酸在果实香气很少时呈增加趋势;随着香气产生的增多而迅速下降;乙烯高峰过后又有增加.脂氧合酶活性随着果实成熟而提高,其活性在乙烯释放达到高峰时达到最大值,之后迅速下降.醇-酰基转移酶活性在果实开始产生香气时迅速增加,之后保持较高活性.     

乙烯促进线粒体呼吸过程中活性氧的作用

外源乙烯能促使绿豆（PhaseolusradiatusL．）黄化幼苗下胚轴线粒体呼吸高峰提前出现及峰值的提高,它对抗氰途径的促进作用比对细胞色素途径的更加显著．外源乙烯作用下绿豆线粒体的超氧阴离子自由基产生速率迅速提高,同时外源的加入使线粒体呼吸高峰的出现明显提前,这从一个侧面表明乙烯对线粒体呼吸的促进作用可能是通过提高线粒体的产生速率而实现的．SOD活性随乙烯处理时间延长而下降,但乙烯作用下的产生并非仅由SOD的活性所决定．     

香蕉一个Ⅲ类酸性几丁质酶基因与果实成熟关系的研究

为了解Ⅲ类酸性几丁质酶基因(MaCHⅢ)与香蕉果实采后成熟过程的相互关系,对经乙烯和1-甲基环丙烯(1-MCP)处理的巴西香蕉果实采后乙烯释放量、Ⅲ类酸性几丁质酶基因(MaCHⅢ)表达以及几丁质酶活性进行了测定.结果显示:(1)乙烯催熟处理的香蕉果实,乙烯释放量比对照处理的果实提前15 d达到高峰;1-MCP处理的香蕉果实,乙烯生物合成和果实成熟明显受到了抑制.(2)外源乙烯加速了MaCHⅢ基因的下调表达和Ⅲ类酸性几丁质酶活性的下降,MaCHⅢ表达量和Ⅲ类酸性几丁质酶活性分别在采后第3天和第4天下降到最小值.(3)1-MCP处理使MaCHⅢ基因呈现上调表达,Ⅲ类酸性几丁质酶活性上升,MaCHⅢ基因表达量和Ⅲ类酸性几丁质酶活性分别在采后18 d和25 d达到高峰.研究表明,MaCHⅢ基因可能与香蕉果实采后成熟呈负相关.     

香蕉ASR的特征和采后表达分析

从香蕉cDNA文库中获得香蕉ASR全长cDNA序列,命名为MaASR。构建遗传进化树发现MaASR与单子叶植物中的芭蕉科植物的亲缘关系较近。对正常成熟和乙烯处理的香蕉果实各时期内源ABA的含量进行测定,结果表明,在正常成熟的香蕉果实中,成熟早期(0-2 d),内源ABA含量相对较低,第8天ABA含量达到最大,随后迅速下降。在乙烯处理的香蕉果实中,ABA含量急剧上升,第3天ABA含量达到高峰,随后逐渐下降。利用荧光定量RT-PCR对MaASR在正常成熟和乙烯处理后的果实中的表达情况进行分析,在自然成熟的果实中,MaASR在采后2 d达到高峰,而后迅速下降,在6-16 d时一直保持较低水平。在经外源乙烯诱导的果实中,MaASR表达水平没有表现出剧烈变化的趋势,整体表达量较低。表明MaASR对乙烯信号有应答,但应答强度较低,其表达趋势与ABA的含量或者信号强度呈负相关。     

1—MCP处理对油桃果实硬度、呼吸及乙烯合成的影响

研究了1-MCP处理对“秦光”油桃果实硬度,呼吸,乙烯,EFE活性的影响。结果表明：1-MCP处理可抑制油桃果实乙烯的合成,显著地降低了乙烯峰值,仅为对照的一半,推迟了乙烯峰和呼吸峰的出现,但提高了呼吸峰值,延缓了果实硬度的下降,介对EFE活性无明显影响。     

香蕉果实成熟软化时果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性的变化

阿拉伯糖是果实软化过程中变化最明显的细胞壁糖残基之一,α-L-阿拉伯呋喃糖苷酶是导致细胞壁多糖中阿拉伯糖残基降解的主要糖苷酶。为阐明该酶在香蕉果实成熟软化中的作用,实验对香蕉贮藏过程中果皮和果肉中该酶活性以及果实硬度、呼吸强度和乙烯释放量的变化进行了研究。结果表明:α-L-阿拉伯呋喃糖苷酶在果实初期的变化很小,到果实硬度开始急剧下降时达到最大,增加量达10倍以上,且果肉中的酶活性大于果皮中;乙烯吸收剂处理延缓了香蕉果实呼吸和乙烯高峰的出现时间,降低了果实硬度、果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性变化的速度和幅度。以上结果表明α-L-阿拉伯呋喃糖苷酶起诱导香蕉果实成熟的作用,在果实的软化中起着十分重要的作用,且其活性受乙烯的调节。     

PRO－LONG涂膜处理对后熟香蕉果实乙烯形成以及其它有关生理变化的影响

香蕉（ＭｕｓａａｃｕｍｉｎａｔａＣｏｌｌａｃｖ．ＤｗａｒｆＣａｖｅｎｄｉｓｈ）果实采后以商业上推荐使用的１．５％Ｐｒｏ－ｌｏｎｇ溶液处理,贮藏于２０℃和７５％相对湿度下,分别测定果实的ＡＣＣ含量、ＭＡＣＣ含量、ＥＦＥ酶活性、乙烯释放、叶绿素含量的变化和果实的硬度变化．结果表明,ＰＲＯ－ＬＯＮＧ处理延缓了香蕉果实果皮的叶绿素降解、硬度的下降以及乙烯释放的增加．在后熟过程中,处理果实的ＡＣＣ含量发生积累．ＡＣＣ含量的高峰在乙烯释放高峰和ＥＦＥ酶活性高峰之前出现．与对照比较,处理果实的ＡＣＣ含量和ＥＦＥ酶活性的高峰延迟了５ｄ出现．在后熟过程中,以Ｐｒｏ－ｌｏｎｇ处理果肉四片,其ＥＦＥ酶活性受部分抑制（抑制率为１９．４５％至４０．５１％）．果实ＭＡＣＣ含量在贮藏起初处于一个较显著水平,随着后熟的发展而逐步增加,但与ＡＣＣ含量的明显增加相比变化是微小的．我们的研究进一步阐明了ＰＲＯ－ＬＯＮＧ涂膜对香蕉果实后熟的影响主要是通过减少氧的供给,部分地抑制了ＥＦＥ酶活性,延缓了乙烯的形成和释放,从而延长了后熟过程．     

硬肉桃果实成熟前后几种与果实软化相关的生理指标的变化

比较桃品种'川中岛白桃'(一般常规桃)和'双久红'(硬肉桃)成熟前后20 d内果肉硬度、乙烯释放量和活性氧代谢有关指标的变化结果表明:两品种桃成熟前后20 d内O2产生速率、H2O2含量、丙二醛(MDA)含量和脂氧合酶(LOX)活性均持续上升,'双久红'果实明显低于'川中岛白桃';在成熟前20 d内两者的超氧化物歧化酶(SOD)和过氧化物~(POD)活性均呈下降趋势,果实成熟后20 d内SOD活性先上升后下降,而POD活性则持续上升;过氧化氢酶(CAT)活性在成熟前20～10 d内上升.以后呈下降趋势.果实成熟后'双久红'的SOD、POD和CAT活性均明显的高于'川中岛白桃'.     

钙对香蕉采后乙烯释放的抑制

本实验用CaCl_2溶液对香蕉(Musa acuminata cf. 'Dwarf Davendish')组织进行真空浸透处理,研究Ca~(2 )对香蕉采后乙烯释放、EFE活性、ACC水平以及ACC/MACC比值的影响。结果表明,Ca~(2 )处理可抑制香蕉果皮和果肉组织乙烯生成,对抑制果皮的乙烯生成尤为明显。Ca~(2 )处理还可降低内源ACC水平,抑制EFE活性。结果还显示,Ca~(2 )处理对组织中ACC/MACC比值有一定影响。     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

鸡传染性法氏囊病病毒研究进展

传染性法氏囊病(Infection bursal disease, IBD)是由鸡传染性法氏囊病毒(Infectious bursal disease virus, IBDV)引起的鸡和火鸡的一种高度接触性传染病,给世界各国的禽养殖业带来了巨大损失.自IBDV发现至今新的变异株不断出现,分子结构的改变导致病毒致病力的改变及宿主对疫苗应答的改变,使得传统的疫苗已不能控制其流行,因此各国学者对其基因组结构和功能进行了广泛深入的研究,并积极研制新型有效的疫苗以达到防治的目的.     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).