The effects of Bacillus thuringiensis Cry6A on the survival, growth, reproduction, locomotion, and behavioral response of Caenorhabditis elegans

Several families of crystal proteins from Bacillus thuringiensis exhibit nematicidal activity. Cry5B protein, a pore-forming toxin, has been intensively studied yielding many insights into the mode of action of crystal protein at molecular level and pathogenesis of pore-forming toxins. However, little attention was paid to Cry6A, another representative nematicidal crystal protein. Cry6A shares very low homology with Cry5B at amino acid sequence and probably acts in a distinct pathway from Cry5B and even the other main commercial crystal proteins. In the current study, we comprehensively investigated the nematicidal properties of Cry6Aa2 against the free-living soil nematode Caenorhabditis elegans and examined the physical response of C. elegans to Cry6Aa2 attack. Our results indicate that Cry6Aa2 exhibits high lethal activity to C. elegans and could cause detrimental effects on C. elegans, including obviously suppressed growth, decreased brood size, and even abnormal motility. Meanwhile, our study additionally shows that C. elegans could defend against the Cry6Aa2 toxin harmful threat through behavioral defense responses, such as reduced oral uptake and physical avoidance. In general, this study suggests that Cry6Aa2 possesses diverse nematicidal properties, which strongly indicates that Cry6Aa2 is a promising potential candidate of nematicidal agent. Moreover, this study highlights the importance of behavioral responses in defense of C. elegans for survival and demonstrates the key role of crystal protein in the interaction of B. thuringiensis–C. elegans. These findings could shed light on understanding the interaction of C. elegans with B. thuringiensis and provide a perfect model to study the role of pathogenic factor in the interaction of pathogen–host.     

NMR studies on novel antitumor drug candidates, deoxoartemisinin and carboxypropyldeoxoartemisinin

Artemisinin and its derivatives, which have been known as antimalarial drugs, have also demonstrated their cytotoxicity against tumor cells. It has been proposed that antitumor activity depends on the lipophilicity of functional group on artemisinin derivatives. Solution structures of two artemisinin derivatives as antitumor drug candidates, deoxoartemisinin and carboxypropyldeoxoartemisinin, were determined by NMR spectroscopy to elucidate structure-activity relationship. According to biological assay, antitumor efficiencies are not dependent upon lipophilicity. Instead, these compounds demonstrated their distinctive structural features of boat/chair conformation and capability to interact with receptors, as they have different efficiencies on antitumor activity. Especially, carboxypropyl moiety or carbonyl moiety in artemisinin derivatives influences the conformation and stability of ring structure. Although the detailed mechanism of antitumor activity by artemisinin derivatives has not been addressed, we suggest that antitumor activity is not determined only with lipophilicity and that artemisinin derivatives have specific target proteins in each type of cancer.     

Non‐dormant Axillary Bud 1 regulates axillary bud outgrowth in sorghum

Tillering contributes to grain yield and plant architecture and therefore is an agronomically important trait in sorghum (Sorghum bicolor). Here, we identified and functionally characterized a mutant of the Non‐dormant Axillary Bud 1 (NAB1) gene from an ethyl methanesulfonate‐mutagenized sorghum population. The nab1 mutants have increased tillering and reduced plant height. Map‐based cloning revealed that NAB1 encodes a carotenoid‐cleavage dioxygenase 7 (CCD7) orthologous to rice (Oryza sativa) HIGH‐TILLERING DWARF1/DWARF17 and Arabidopsis thaliana MORE AXILLARY BRANCHING 3. NAB1 is primarily expressed in axillary nodes and tiller bases and NAB1 localizes to chloroplasts. The nab1 mutation causes outgrowth of basal axillary buds; removing these non‐dormant basal axillary buds restored the wild‐type phenotype. The tillering of nab1 plants was completely suppressed by exogenous application of the synthetic strigolactone analog GR24. Moreover, the nab1 plants had no detectable strigolactones and displayed stronger polar auxin transport than wild‐type plants. Finally, RNA‐seq showed that the expression of genes involved in multiple processes, including auxin‐related genes, was significantly altered in nab1. These results suggest that NAB1 functions in strigolactone biosynthesis and the regulation of shoot branching via an interaction with auxin transport.     

副产物途径的缺失对大肠杆菌合成D-1,2,4-丁三醇的影响

【目的】敲除副产物途径,提高重组大肠杆菌D-1,2,4-丁三醇(D-1,2,4-Butanetriol,BT)产量。【方法】利用Red重组技术敲除木糖途径xyl AB基因及2-酮-3-脱氧木糖酸代谢途径的yag E及yjh H基因,考察其对重组菌生长、BT生产及副产物积累的影响。【结果】敲除xyl AB基因后,重组菌生物量降低57%,BT产量降低20%,单位菌体产量提高84%,木糖酸积累量提高52%。yag E或yjh H基因单独缺失重组菌生物量分别提高10%和5%,BT产量提高36%和14%。基因共同缺失后重组菌生物量降低了21%,BT产量提高184%,达到2.44 g/L,单位菌体产量提高258%。而共同敲除两途径,生物量降低了72%,虽然单位菌体产量提高了约4倍,但BT产量仅提高43%。p H调控下,重组菌木糖酸积累量下降,BT产量进一步提高,最高达3.11 g/L。【结论】xyl AB基因缺失后,虽有利于提高BT途径的效率,但由于木糖无法进入PPP途径及木糖酸积累,造成生物量降低,不利于BT合成。单独敲除yag E或yjh H后BT产量略有提高,而共同敲除这两基因更为有效地调整碳流向BT合成偏转。两途径共同敲除利于BT的合成,但由于菌体量的减少,无法大量获得BT。     

人工湿地在生态城市建设中的作用

生态城市的建设依赖于科学利用有限资源。随着我国城市化进程加快,水体污染日益严重,加剧了水资源的短缺。人工湿地是利用生物自净功能,低投入、低运行费、低能耗的环保型的污水处理技术。不仅可进行水资源的循环利用,而且美化环境、保护生物多样性。本文分析提出,人工湿地是生态城市建设中水资源利用的最有效模式,应大力发挥人工湿地在我国生态城市建设中的作用。     

病毒衣壳结构亚单位的种类数与三角形剖分数关系的研究和探讨

本文报道了在正廿面体病毒衣壳中,当蛋白结构亚单位以“三聚体”的形式聚集在单位三角形(?)时,其亚单位的种类数应等于该病毒的三角形剖分数值。     

马尾松雌球果的发生和早期发育研究

采用常规石蜡制片技术对马尾松雌球果的发生和早期发育进行了研究。结果表明：雌球果原基发生时间为10月中旬,不同的树龄和着生部位,其发生时间不同。雌球果原基与营养茎端在外部形态及内部细胞组织学分区结构有明显差异。营养茎端外形扁平,内部顶端分生组织结构有顶端原始细胞区、中央母细胞区、形成层状过渡区、周围分生组织区及肋状分生组织区5个明显的分区;而雌球果原基外形呈圆锥状,内部结构只有套层和髓区。12月初,最初的苞片原基在雌球果原基的鳞片的叶腋处产生,之后其由基部向顶部连续发生。翌年1月初,在苞片原基的叶腋处,珠鳞原基发生,发生方向亦为向顶发育。2月底,苞片体积不再发生变化,珠鳞膨大端的基部的近轴面分化出2个倒生胚珠。从雌球果原基发生到胚珠分化历时4个多月。亚热带的冬季气候对马尾松雌球果的生长发育没有明显的抑制作用。     

社会竞争失败病因学的抑郁症树鼩模型

抑郁症是一种常见精神疾病,主要表现为持续两周以上的情绪低落。世界卫生组织预测在2030年抑郁症的疾病负担将高居所有疾病、伤残总负担的榜首。抑郁症面临三大难题:1)发病机理不完全清楚,因而缺乏有效的预测预防途径和生物学诊断;2)现有单胺类抗抑郁症药物起效慢,也可能导致患者自杀风险增加;3)缺乏副作用小的非单胺类快速起效抗抑郁症药物。针对这三大难题,长期以来,应用抑郁症啮齿类模型的众多研究并未取得实质性进展,至少部分因素归咎于啮齿类与人类大脑功能的极大种属差异。树鼩是灵长类近亲,具有更接近于人类的大脑功能。本文针对抑郁症发病机理假说、临床表象和抗抑郁症药物疗效等内容,综述了社会竞争失败病因学的抑郁症树鼩模型可能会具有更好的疾病同源性、表象一致性和药物预见性。这一被长期忽视的抑郁症树鼩模型尽管还需要进一步完善,但对其进一步深入研究可能为解决抑郁症的三大难题提供了一条新途径。     

籼型常规早稻穗分化期低温对颖花形成和籽粒充实的影响

以籼型常规早稻中嘉早17为材料,于盆栽条件下采用人工气候箱控温,在水稻穗分化一次枝梗原基分化期(Ⅱ)与花粉母细胞减数分裂期(Ⅵ)进行17和20 ℃的低温胁迫处理,研究不同低温对水稻枝梗、颖花分化与退化及籽粒充实的影响.结果表明： 与对照相比,不同低温处理均显著降低每穗枝梗及颖花分化数和现存数,颖花现存数降幅为7.2%～12.4%,同时增加了枝梗和颖花的退化数,影响了花粉活性、花药开裂等花器官发育,导致籽粒充实不良,以17 ℃低温胁迫效应更明显.穗分化Ⅵ期低温处理总枝梗和颖花分化数与现存数低于穗分化Ⅱ期,但二次枝梗和颖花退化数较多,颖花退化数较穗分化Ⅱ期高11.6%;穗分化Ⅱ期低温处理穗部籽粒结实率显著低于穗分化Ⅵ期,降幅达3.7%,主要与花粉粒活性、柱头花粉散落数、花药开裂系数和籽粒充实度受低温影响较大有关.另外,穗分化Ⅱ、Ⅵ两时期受17 ℃低温胁迫效应大于20 ℃.综合穗分化两时期低温胁迫效应的差异,生产中需加强相应栽培措施的调控.     

不同农田生态系统土壤碳库管理指数的研究

讨论不同农田生态系统的土壤活性碳库和碳库管理（ＣＰＭＩ）,结果表明,不同农田生态系统的土壤ＣＰＭＩ明显受施肥、气候、土壤利用方式,耕种年限等因素的影响。供试土壤的活性碳含量范围为０．４９～４．９９ｍｇ／ｇ,土壤ＣＰＭＩ为５１．６～１６５。不同施肥地红壤ＣＰＭＩ的影响顺序为绿肥（ＧＭ）〉概肥（ＦＹＭ）〉ＦＹＭ－ＮＰＤ〉参考（ＲＥＦ）〉ＮＰＫ〉对照（ＣＫ）,在水稻土中,共相应的影响顺序为,稻草（ＲＳＣ