2014.07.23【英译中】SCI 连载之十

小妮丫头 (流火) 路人甲
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发表于:2014-07-23 16:03 [只看楼主] [划词开启]

2014.07.23【英译中】SCI 连载之十


The concept based on bacterial ribosome engineering, as described above, has been applied to fungi to produce secondary metabolites. For example, introduction of gentamicin resistance into the marine-derived fungal strain Penicillium purpurogenum G59 effectively activated silent gene clusters for secondary metabolites (Chai et al.2012). Although gentamicin did not inhibit this strain G59 during routine testing, treatment of G59 spores with high concentrations of gentamicin, in combination with dimethyl sulfoxide, inhibited strain growth, allowing the development of gentamicin-resistant colonies on agar plate. This method produced four antitumor secondary metabolites not found in the secondary metabolites of other P. purpurogenum strains. In addition, hygromycin B-resistant mutants of Monascus pilosus NBRC 4520 that exhibited enhanced production of secondary metabolites could be isolated using the general method used to obtain drug-resistant mutants in bacteria (Hosaka and Mizukami, unpublished data), because hygromycin B is an aminoglycoside antibiotic that potently inhibits protein synthesis in both prokaryotic and eukaryotic cells (Gonzalez et al. 1978). These findings indicate that modulation of ribosomal function may be applicable to a variety of fungi to elicit their potential secondary metabolism.

就如上面所说,细菌核糖体工程的观念已经用在真菌上来生产次级代谢物。例如,在海源性真菌Penicillium purpurogenum G59中导入庆大抗性基因能够有效激活次级代谢基因簇。虽然庆大霉素不会抑制G59菌株的常规试验,但对G59孢子进行高浓度庆大霉素处理,同时还有DMSO,则会抑制菌株的生长,最后耐庆大霉素的克隆子就会在琼脂糖平板上生长。这种方法发现了在其他P. purpurogenum菌中没有发现的4个具有抗肿瘤活性的次级代谢物。除此之外,Monascus pilosus NBRC 4520hygromycin B突变子表现出增强次级代谢物产生的能力,因此可以通过常规获得细菌耐药突变的方法分离得到,因为hygromycin B是一种氨基糖苷抗生素,不管是在原核还是在真核细胞当中,都具有潜在抑制蛋白合成的能力。这些发现说明,核糖体功能的调整可能适用于多种真菌来挖掘它们潜在的次级代谢机制。

 

A new insight into the silent gene activation in the eukaryotic microorganisms is also coming from the ectopic ppGpp expression. The bacterial alarmone ppGpp, produced by RelA-SpoT homologue (RelA or RSH) on the ribosome in response to nutrient limitation, is a key signal factor to initiate the onset of bacterial secondary metabolism (Bibb2005;Ochi 2007). Although relA and RSH, the genes encoding ppGpp synthetase, are distributed widely in bacteria and plants (Givens et al. 2004; Takahashi et al. 2004; Tozawa and Nomura2011; vanderBiezenetal.2000), neither of these genes, nor ppGpp itself, has yet been identified in animals or eukaryotic microorganisms. Despite the essential lack of a relA-spoT homologue and ppGpp in the yeast S. cerevisiae, its heterologous expression of a relA-spoT homologue (SjRSH) isolated from the halophilic plant Suaeda japonica resulted in the accumulation of ppGpp, accompanied by the enhancement of tolerance against various stressors, including osmotic stress, ethanol, and freezing (Ochi et al.2012; Yamada et al.2003). Low levels of ppGpp [10–20 pmol (mg dry weight) −1 ] were sufficient for cellular stress tolerance without affecting growth rate (Ochi et al.2012). These results raise an intriguing possibility that the ppGpp system can be applicable to the silent gene activation in such eukaryotic microorganisms as fungi.

原核微生物中沉默基因的激活的一种新视角来自于异位ppGpp的表达。细菌的信号子ppGpp,由核糖体上RelA-SpoT类似物产生负责应答营养限制,是细菌次级代谢机制起点开始的关键信号因子。虽然负责编码ppGpp合成酶的relARSH基因在细菌和植物当中分布的十分广泛,不管是这些基因还是ppGpp自身,到目前为止还没有在动物或者真核微生物中分离得到。不管本质上是由于酵母菌S. cerevisiae中缺少relA-spoT类似物和ppGpp,通过一定程度对多种应激因子(包括渗透应力、乙醇、冰冻)的耐受能力的加强,它在嗜盐植物Suaeda japonica中进行了relA-spoT类似物的异源表达并得到一定浓度的ppGpp。低水平的ppGpp [10–20 pmol (mg 干重) −1 ]能在不影响生长速度的情况下满足细胞应激耐受力。这些结果都导向一种吸引人的可能性,ppGpp系统能够适用于真核微生物如真菌中沉默基因的激活。

分类: 英语

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