反义RNA介导的大肠杆菌非必需基因rpsF的基因沉默

【目的】探讨反义RNA技术介导的大肠杆菌非必需基因rpsF基因沉默导致菌体生长受抑制的原因。【方法】将rpsF基因5'端41-230 bp的片段反向插入带有末端配对结构的反义表达载体pHN678,获得重组质粒,导入大肠杆菌宿主获得反义RNA菌株Escherichia.coli/pHNF,并用诱导剂IPTG诱导反义RNA表达,通过与对照菌E.coli/pHN678的液体生长状态差异判断菌体生长表型;采用Real time RT-PCR方法跟踪分析转录水平。【结果】构建了针对rpsF的反义RNA菌株,且其生长受抑制程度与IPTG浓度呈正相关。IPTG浓度为100μmol/L时,菌体生长未受抑制,但靶基因rpsF的mRNA量降低了36%,而rpsR是位于同一操纵子下游的必需基因,其转录水平却未受影响;IPTG浓度为200μmol/L时,菌体生长明显受抑制,经分析发现rpsR转录水平降低了12%。【结论】反义RNA菌株E.coli/pHNF生长受抑制的原因是由于此反义RNA引起了同一操纵子下另一必需基因rpsR的转录水平降低。     

水稻胚胎形成期间蛋白质和RNA合成活力的变化

用~3H-亮氨酸和~3H-尿苷标记不同发育时期的稻胚,发现蛋白质合成活力呈四阶段变化;各种RNA的合成与胚胎各发育阶段密切有关。α-鹅膏蕈碱(1.0μg/ml)对稻胚RNA合成的抑制作用在开花后7、15和18天较强,13天时很弱。在水稻胚胎形成期间,胚细胞蛋白质合成活力高峰先后出现于胚分化后期(开花后11天)和成熟中期(18天);mRNA的合成在分化初期(7天)和成熟中期(15～18天)较强;而rRNA和/或tRNA的合成高峰则出现在胚胎器官原基分化已经完成时(13天)。     

Induction of defence gene expression by oligogalacturonic acid requires increases in both cytosolic calcium and hydrogen peroxide in Arabidopsis thaliana

Responses to oligogalacturonic acid (OGA) were determined in transgenic Arabidopsis thaliana seedlings express-ing the calcium reporter protein aequorin. OGA stimulated a rapid, substantial and transient increase in the concentration of cytosolic calcium ([Ca^2 ]cyt) that peaked after ca. 15 s. This increase was dose-dependent, saturating at ca. 50 μg Gal equiv/ml of OGA. OGA also stimulated a rapid generation of H202. A small, rapid increase in H2O2 content was followed by a much larger oxidative burst, with H2O2 content peaking after ca. 60 min and declining thereafter. Induction of the oxidative burst by OGA was also dose-dependent, with a maximum response again being achieved at ca. 50 μg Gal equiv/mL. Inhibitors of calcium fluxes inhibited both increases in [Ca^2 ]cyt and [H2O2], whereas inhibitors of NADPH oxidase blocked only the oxidative burst. OGA increased strongly the expression of the defence-related genes CHS,GST, PAL and PR-1. This induction was suppressed by inhibitors of calcium flux or NADPH oxidase, indicating that increases in both cytosolic calcium and H2O2 are required for OGA-induced gene expression.     

The C termini of Arabidopsis cryptochromes mediate a constitutive light response

Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair. However, cryptochromes lack photolyase activity and are characterized by distinguishing C-terminal domains. Here we show that the signaling mechanism of Arabidopsis cryptochrome is mediated through the C terminus. On fusion with beta-glucuronidase (GUS), both the Arabidopsis CRY1 C-terminal domain (CCT1) and the CRY2 C-terminal domain (CCT2) mediate a constitutive light response. This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles. We propose that the C-terminal domain of Arabidopsis cryptochrome is maintained in an inactive state in the dark. Irradiation with blue light relieves this repression, presumably through an intra- or intermolecular redox reaction mediated through the flavin bound to the N-terminal photolyase-like domain.     

水貂GH基因SNP_S与皮张长度的相关性研究

以水貂生长激素(GH)基因作为控制水貂皮张长度性状主基因的候选基因,以大兴安岭水貂养殖基地养殖的水貂群为试验材料,通过PCR-SSCP方法对GH基因进行多态性检测。在该基因内含子1中发现1处碱基突变:C→A,并检测到3种基因型(AA、AB、BB),BB基因型个体与AA基因型个体皮张长度有一定的差异(P0.05)。在外显子2中发现2处碱基突变:T→A、C→G,并由此检测到了3种基因型,分别命名CC、CD、DD,但3种基因型对水貂皮长的影响没有显著的差异(P0.05)。统计各基因型之间的组合给水貂皮长带来的影响时,发现多数组合基因型对所检测的水貂皮长有显著影响(P0.05)。     

五唇兰雌配子体发育和胚胎发生的研究

五唇兰的胚珠倒生型,具薄珠心,两层珠被。胚囊发育为双孢子葱型,成熟胚囊８核。从传粉到受精约５０ｄ,正常双受精。胚具５－６细胞的胚柄,种子成熟时胚柄及胚乳核消失,成熟种子只具单层细胞的种皮和一个未分化的珠珠形胚。     

波罗的海希瓦氏菌AI-2/LuxS对生物被膜和致腐的调控

【目的】波罗的海希瓦氏菌(Shewanella baltica)是冷藏海产鱼类的特定腐败菌。研究群体感应信号AI-2/Lux S对鱼源S.baltica生物被膜和致腐的调控作用。【方法】扩增SB11分离株的lux S基因,用自杀性质粒构建lux S基因缺失株,通过结晶紫染色、珠涡流法、显微镜观察和HPLC,比较分析野生株与缺失株△lux S在4°C和28°C下生物被膜形成、粘附能力、泳动性和致腐产物的差异。【结果】S.baltica SB11中扩增获得lux S基因,生物信息学分析显示Lux S蛋白由169个氨基酸构成,含有保守的His-Thr-Leu-Glu-His(HTLEH)模体和关键氨基酸位点,蛋白三维空间结构与其他细菌相似。与野生株相比,△lux S缺失株上清荧光信号散失,但不影响生长,生物被膜形成期和成熟期的含量显著低于野生株,在4°C培养96 h和28°C培养24 h被膜分别减少20.1%和27.9%。缺失株在不锈钢片的粘附能力明显减弱,其中在4°C培养72 h和28°C培养24 h后的粘附量比野生株分别减少6.48%和6.57%。荧光显微镜观察发现,野生株能快速粘附于玻璃片,聚集形成大量生物被膜,而△lux S仅形成平坦稀疏的被膜,粘附细菌降低,CLSM证实野生株和△lux S的成熟被膜厚度分别为68.95μm和36.44μm。并且,△lux S株在4°C和28°C下泳动性均显著强于野生株。然而,野生株和△lux S株三甲胺和腐胺积累无差异。【结论】鱼源S.baltica中Lux S蛋白保守,AI-2/Lux S参与被膜、粘附能力及泳动性等多种生物被膜形成相关的调控作用,然而不是该菌致腐能力的功能性群体感应信号。     

CO2浓度升高对不同品种水稻镉吸收和根形态的影响

为了探讨CO2浓度升高下不同水稻品种荣优398 (RY)和粤杂889(YZ)吸收重金属Cd差异性的原因,利用水培试验研究了不同浓度Cd处理下两种水稻吸收Cd的差异及根形态的变化特征.结果表明:低Cd处理(5、10、20 μmol·L-1)显著增加水稻生物量;当Cd浓度高于50 μmol·L-1时,Cd胁迫效果开始显现,水稻生物量减少.CO2浓度升高显著增加了水稻的生物量,增加了YZ茎Cd含量而降低了RY茎Cd含量.在5～200 μmol·L-1的Cd浓度下,CO2浓度升高增加了YZ活性根在总根长中的比例,降低了RY活性根的比例.CO2浓度升高下不同水稻品种根形态的变化是导致其对Cd吸收差异性的原因之一.