Small bending,big curvature

<正>The classical "Cholodny-Went theory" predicted that directional stimuli trigger the redistribution of auxin, which governs the differential growth of plant organs through potent effects on cell expansion, thereby establishing an"auxin-then-growth" paradigm; this theory has been validated for both gravitropism and phototropism in plants(reviewed in Muthert et al., 2020).     

Selective pericentromeric heterochromatin dismantling caused by TP53 activation during senescence

Cellular senescence triggers various types of heterochromatin remodeling that contribute to aging. However, the age-related mechanisms that lead to these epigenetic alterations remain elusive. Here, we asked how two key aging hallmarks, telomere shortening and constitutive heterochromatin loss, are mechanistically connected during senescence. We show that, at the onset of senescence, pericentromeric heterochromatin is specifically dismantled consisting of chromatin decondensation, accumulation of DNA breakages, illegitimate recombination and loss of DNA. This process is caused by telomere shortening or genotoxic stress by a sequence of events starting from TP53-dependent downregulation of the telomere protective protein TRF2. The resulting loss of TRF2 at pericentromeres triggers DNA breaks activating ATM, which in turn leads to heterochromatin decondensation by releasing KAP1 and Lamin B1, recombination and satellite DNA excision found in the cytosol associated with cGAS. This TP53–TRF2 axis activates the interferon response and the formation of chromosome rearrangements when the cells escape the senescent growth arrest. Overall, these results reveal the role of TP53 as pericentromeric disassembler and define the basic principles of how a TP53-dependent senescence inducer hierarchically leads to selective pericentromeric dismantling through the downregulation of TRF2.     

发酵液内氨甲酰妥布拉霉素的定量测定

报道了应用一种以测量图象面积为指标的Ｚｙ－３００Ａ多功能抑菌圈测量仪,能够精确、稳定、快速地测定发酵液经薄层层析生物显迹后单组分氨甲酰妥布拉霉素的抑菌斑面积,然后从绘制的标准曲线中直接读取氨甲酸妥布拉霉素在发酵液中的含量,从而排除了其他组分对测定的干扰。试验证明,用Ｚｙ－３００Ａ多功能抑菌圈测量仪测定抗生素薄层层析生物显迹的抑菌斑,具有线性宽、精密度高、重复性强、操作简单方便等优点．本方法的建立为抗生素的纯品检定和多组分抗生素发酵、分离和纯化提供了准确的定量数据．     

烷化剂NTG诱变虾青素产生菌红法夫酵母的研究

虾青素是一种很有效的生物抗氧化剂和某些生物的天然着色剂,应用前景广阔。红法夫酵母是 生产虾青素的一个来源,优点颇多。天然菌株虾青素产量较少,缺少实用价值。实验采用烷化剂ＮＴＧ 诱变红法夫酵母,筛选出类胡萝卜素产量高的诱变株。用薄层层析对红法夫酵母产生的色素及其皂 化产物进行分析,并对各个成分的扫描光谱进行了比较。认为红法夫酵母产生的类胡萝卜素成分主 要是虾青素及虾青素二酯,还有一部分β－胡萝卜素。同时,还对虾青素产生的时相和ＢＨＴ对虾青素 光分解的保护作用进行了初步研究。     

嗜热细菌Clostridium thermocellum阿魏酸酯酶基因的克隆、异源表达及酶学特性分析

【目的】阐明嗜热细菌Clostridium thermocellum Xyn Z蛋白的阿魏酸酯酶催化域的酶学特性,为其在生物质能源及其它发酵工业中的应用奠定基础。【方法】分别构建了C.thermocellum Xyn Z的阿魏酸酯酶催化域(FAE)及该阿魏酸酯酶催化域和碳水化合物结合域(FAE-CBM6)编码基因的原核表达载体,并在大肠杆菌菌株BL21(DE3)中异源表达,在此基础上分析比较了温度、pH、底物、金属离子及CBM6结合域对阿魏酸酯酶活性的影响。【结果】重组FAE酶及FAE-CBM6酶发挥催化活性的适宜pH值为5.0-9.0,适宜温度为50-70°C,它们对不同金属离子的响应有差异。【结论】在同一反应条件下,FAE-CBM6酶的酶活均比FAE高,说明CBM6结合域的存在对于阿魏酸酯酶活性有促进作用。