Heterochromatic silencing and HP1 localization in Drosophila are dependent on the RNAi machinery

Genes normally resident in euchromatic domains are silenced when packaged into heterochromatin, as exemplified in Drosophila melanogaster by position effect variegation (PEV). Loss-of-function mutations resulting in suppression of PEV have identified critical components of heterochromatin, including proteins HP1, HP2, and histone H3 lysine 9 methyltransferase. Here, we demonstrate that this silencing is dependent on the RNA interference machinery, using tandem mini-white arrays and white transgenes in heterochromatin to show loss of silencing as a result of mutations in piwi, aubergine, or spindle-E (homeless), which encode RNAi components. These mutations result in reduction of H3 Lys9 methylation and delocalization of HP1 and HP2, most dramatically in spindle-E mutants.     

RNA干扰沉默Ghrelin基因对仔猪胃酸分泌的调节作用

[目的]研究生长素(Ghrelin)基因沉默对仔猪胃酸分泌的调节作用,为防治仔猪断奶后某些消化系统功能障碍或分泌异常研究提供新靶点,进而阐明Ghrelin对胃酸分泌的调节作用机制.[方法]采用脂质体将RNA干扰沉默的shGhrelin转染体外培养的猪胃黏膜上皮细胞,优化确立最佳转染条件,并通过荧光定量RT-PCR检测shGrelin转染对胃黏膜上皮细胞中Ghreli基因mRNA表达及H+-K+-ATPase(质子泵)活性的影响.[结果]质粒(shGhrelin)与脂质体(Lipofectamine 2000)的最佳转染比例为1:3,最佳转染时间24h.与正常对照组相比,以shGhrelin转染胃黏膜上皮细胞后,其Ghrelin基因mRNA的表达显著降低(P<0.05,下同),H+-K+-ATPase活性也显著下降.[结论]采用RNA干扰技术能沉默胃黏膜上皮细胞Ghrelin基因表达和抑制H+-K+-ATPase活性,表明Ghrelin对胃酸分泌具有重要的调节作用.     

大豆RACK1基因RNAi载体构建及植株转化

[目的]筛选大豆RACK1基因的RNAi突变体,为研究RACK1基因在大豆生长发育过程的调控作用提供依据.[方法]采用RT-PCR克隆大豆叶片RACK1基因核心保守序列片段,以植物表达载体pCAMBIA 1301为基本载体,构建抑制大豆RACK基因表达的RNAi载体.通过农杆菌介导转入大豆子叶节,经潮霉素筛选转基因植株,利用PCR、Southern blot及RT-qPCR进行转基因植株检测.[结果]克隆获得大豆RACK1基因核心保守序列片段432 bp;将该基因片段连接到pCAMBIA1301表达载体内含子两侧,通过酶切分析,RNAi载体构建正确.通过农杆菌介导,将该载体转入大豆中黄13号,获得23个转基因大豆株系;经PCR和Southern blot检测,确定大豆RACK1基因RNAi片段已融合到大豆基因组中.经定量RT-qPCR分析,不同转基因大豆株系RACK1基因mRNA的表达量具有明显差异,其在株系5的表达量最高,为对照的68.5%;株系7最低,降至对照的19.9%.[结论]成功构建了大豆RACK1 RNAi表达载体并导入大豆基因组中,获得23个农杆菌介导的RACK1 RNA干扰表达的大豆转基因植株,为研究RACK1基因在大豆生长发育过程中的功能和作用奠定了基础.     

Strawberry FaEtr2 gene RNAi expression vector construction and genetic transformation

The short hairpin RNA (shRNA) expression vector of the FaEtr2 gene was constructed by inserting the sense fragment into the constructed antisense vector of FaEtr2 (pBI121-Anti-Etr2) in sense orientation. The constructed RNA interference (RNAi) expression vector was transformed into Agrobacterium fumefeciens LBA4404 and used to infect strawberry leaves. Using in vitro plantlet leaves as explants, the transformation conditions of All-Star strawberry were studied systemically. The results showed that infecting the leaves with A. fumefeciens resuspension liquid of OD₆₀₀ = 1.0 by pre-culturing for 3 d, co-culturing for 3 d, infecting for 10 min, and adding acetosyringone (AS) 50–100 μmol·L⁻¹ was suitable for genetic transformation of All-Star strawberry. Seven lines of transgenic plants were preliminarily identified by PCR and β-glucurondiase (GUS) histochemical staining.     

A similarity between viral defense and gene silencing in plants

Gene silencing in plants, in which an endogenous gene is suppressed by introduction of a related transgene, has been used for crop improvement. Observations that viruses are potentially both initiators and targets of gene silencing suggested that this phenomenon may be related to natural defense against viruses. Supporting this idea, it was found that nepovirus infection of nontransgenic plants induces a resistance mechanism that is similar to transgene-induced gene silencing.     

油棕病毒诱导的基因沉默体系的建立及优化

为开展油棕油脂代谢调控相关基因鉴定研究,以油棕八氢番茄红素脱氢酶基因（phytoene desaturase gene,PDS）作为报告基因,探索以病毒载体TRV为载体在油棕胚状体上应用病毒诱导基因沉默（virus-induced gene silencing,VIGS）的可能性,并对油棕胚状体VIGS体系的相关参数进行优化。结果显示：以EHA105为菌种、侵染菌液OD600=0.5、侵染时间5 min、乙酰丁香酮（AS）质量浓度20 mg/L、共培养48 h、侵染后培养时间为12 d能取得最佳的基因沉默效果。在此基础上,利用优化后的VIGS体系对油棕二酰甘油酰基转移酶基因（diacylglycerol acyltransferase gene,DGAT）进行沉默,取得了预期的基因沉默效果。     

重组RNA干扰表达载体的构建与鉴定

干扰(RNA interference,RNAi)是指在进化过程中高度保守的、由双链RNA诱发的、同源mRNA高效特异性降解的现象。本研究以稻纵卷叶螟可溶型海藻糖酶基因(Cm Tre1)为靶标,设计RNAi靶位点并将其命名为Cm Tre1*,在其两端分别添加Bam H I与Spe I酶切位点并进行人工合成,然后经双酶切后与p1301植物表达载体连接,构建重组表达载体p1301-Cm Tre1*。PCR、双酶切和测序鉴定结果证明重组表达载体p1301-Cm Tre1*构建成功,并将其成功转入农杆菌LBA4404,构建基因工程菌。用含有p1301-Cm Tre1*质粒的农杆菌LBA4404浸染中花11号水稻的愈伤组织,经过愈伤组织的抗性筛选、分化和植株再生,获得26株阳性转基因植株。用取食非转基因水稻的稻纵卷叶螟作为对照,用实时荧光定量PCR方法分株测定取食转基因水稻稻纵卷叶螟体内Cm Tre1基因的mRNA表达水平,并检测其体内海藻糖酶活性变化。结果显示,相较于对照组,取食转基因水稻稻纵卷叶螟体内Cm Tre1基因表达量下降了44.79%,海藻糖酶活力平均下降了14.94%。研究结果表明转基因水稻的RNA干扰效应相当明显,能对取食其叶片的稻纵卷叶螟Cm Tre1基因起到明显的沉默作用。     

番茄脯氨酸脱氢酶基因的克隆与RNAi植物表达载体的构建

[目的]克隆了脯氨酸脱氢酶ProDH基因的全长cDNA,构建了ProDH基因的RNA干扰植物表达载体,并转化到农杆菌.[方法]以“耐运2000番茄”幼苗为试材,根据GenBan中公布的番茄脯氨酸脱氢酶ProDH基因的序列信息设计了一对特异性引物,克隆了该基因的全长cDNA,分析基因序列选择正反向片段并扩增,并通过酶切、连接的方法构建了ProDH基因的RNA干扰植物表达载体PBI121-PDHi利用冻融法将表达载体转化到农杆菌EHA105中.[结果]所克隆到的ProDH基因片段长2 001 bp,其中CDS为1 491 bp,编码380个氨基酸.测序结果与公布序列同源性100％,因此可以用来构建干扰载体;通过酶切与测序鉴定,证明表达载体构建成功.[结论]经特异性引物扩增检测,证明表达载体已转入农杆菌,为进一步的研究该基因奠定了基础.     

甘蓝脯氨酸脱氢酶基因克隆与RNAi表达载体构建

通过RT-PCR、同源克隆和RACE等方法由甘蓝总RNA扩增得到了甘蓝脯氨酸脱氢酶基因cDNA全长(1 719 bp),其中包含了一个1 497 bp的完整开放阅读框,编码498个氨基酸,与已发表的十字花科植物ProDH基因均具有85%以上的同源性。在此基础上设计并克隆干扰片段,利用酶切连接的方法将该基因干扰片段正反向插入到载体pFGC-1008的GUS内含子两侧,经限制性内切酶酶切和测序鉴定,证明植物表达载体pFGC-gPDH已构建成功,为进一步研究该基因的功能创造了条件。     

家蚕UDP葡萄糖基转移酶Bmugt2基因的克隆与RNA干涉

糖基化在大多体内复合物的失活和排出过程中起重要的作用.报道家蚕一UDP葡萄糖基转移酶基因Bmugt2的特征和可能的功能.该基因编码序列长1 578 bp(登录号:FJ237534),翻译525个氨基酸,推定的氨基酸与UGT家族的其它氨基酸有约30%的一致性.RT-PCR检测该基因主要在家蚕丝腺中表达,应用体外转录合成的基因dsRNA干涉家蚕后,丝腺中基因的表达明显降低,但对家蚕茧色无明显的可见影响.     

miRNA-mediated gene silencing by translational repression followed by mRNA deadenylation and decay

microRNAs (miRNAs) regulate gene expression through translational repression and/or messenger RNA (mRNA) deadenylation and decay. Because translation, deadenylation, and decay are closely linked processes, it is important to establish their ordering and thus to define the molecular mechanism of silencing. We have investigated the kinetics of these events in miRNA-mediated gene silencing by using a Drosophila S2 cell-based controllable expression system and show that mRNAs with both natural and engineered 3' untranslated regions with miRNA target sites are first subject to translational inhibition, followed by effects on deadenylation and decay. We next used a natural translational elongation stall to show that miRNA-mediated silencing inhibits translation at an early step, potentially translation initiation.     

野生罂粟BBE基因克隆及RNAi载体构建

以野生罂粟(Papaver somniferum)试管苗幼叶为材料,用Trizol试剂盆提取总RNA,通过RT-PCR法获得BBE基因的cDNA片段,序列分析表明,所获得的cDNA序列全长1 608 bp,具有完整的开放阅读框(ORF),编码536个氨基酸,经blast检索该片段与GenBank中的小檗碱桥酶基因BBE(AF025430)同源性为94.84%.以中间载体pHANNIBAL和植物表达载体pART27为基础,构建了CaMV-35S启动子驱动的含小檗碱桥酶基因片段反向重复序列的RNAi双元表达载体pARB,为培育低吗啡,高蒂巴因的罂粟新品系奠定了基础.     

苎麻CCoAOMT基因干扰表达载体构建及对烟草的转化

根据已克隆的苎麻CCoAOMT(咖啡酰辅酶-A-氧甲基转移酶)基因cDNA序列,以其编码纤维素合成酶底物结合和催化合成结构域的 cDNA 序列为目标,采用PCR扩增方法引入克隆的酶切位点,分别将其正、反方向克隆到植物RNA干扰表达质粒PFGC5941 T-DNA上CHSA内含子两侧,构建了植物表达苎麻CCoAOMT基因的干扰重组Ti载体.将该载体转入根癌农杆菌LBA4404后,采用农杆菌介导法对木质素研究的模式烟草WS38进行了遗传转化,抗性筛选和分子检测表明,成功获得了转基因植株.转基因植株生长延缓,表明可能存在基因表达干扰现象.     

红鳍东方鲀去乙酰化酶SIRT3基因的克隆及原核表达

从红鳍东方鲀(Takifugu rubripes)肝脏组织中提取总RNA,通过RT–PCR扩增,获得SIRT3基因的编码阅读框(ORF),用原核表达载体p ET32a(+)构建p ET32a/SIRT3重组质粒,用异丙基–β–D–硫代半乳糖苷(IPTG)将重组质粒p ET32a/STRT3在大肠杆菌Rosetta(DE3)进行诱导表达,并用镍柱纯化融合表达蛋白。结果显示,红鳍东方鲀SIRT3基因(tr SIRT3)ORF区大小为1 263 bp大小,编码420个氨基酸。经IPTG诱导表达后,获得1个带组氨酸(His)标签的融合蛋白,目的蛋白主要存在于上清溶液中,为可溶性表达。用镍离子亲和层析柱对重组蛋白进行纯化,获得了相对分子质量约66 000的重组蛋白。