Milk-clotting activity of cucumisin,a plant serine protease from melon fruit

Cucumisin (EC 3.4.21.25) isolated from prince melon fruit is a plant serine protease. Its milk-clotting activity was compared with plant cysteine proteases such as papain (EC 3.4.22.2) and ficain (EC 3.4.22.3). Cucumisin was more stable than papain under the condition of pH 7.1, 37‡C for 24 h. The milk-clotting activity of cucumisin was the same to that of papain and was half value of that of ficain.     

Relation between phytohormone level and vascular bridge differentiation in graft union of explanted internode autografting

Development of the graft union of explanted internode autografting of cucumber (Cucumis sativus Linn.) culturedin vitro is regulated by plant hormones exogenously added to the media. The levels of auxin (indole-3-acetic acid, IAA) and zeatin plus zeatin riboside (Z + ZR) in graft unions and in 4 parts of the graft union have been analyzed by ELSA assay. Results show that vascular bundle regeneration in the graft union is co-regulated by IAA and Z + ZR. Differentiation of vascular bridge across the graft interface requires higher level of IAA and IAA/ (Z + ZR) ratio than that of anastomosing bundle, indicating that plant hormones are limiting and controlling factors for the development of graft union.     

激光照射对白兰瓜种子萌发期淀粉酶活性的影响

用532.0 nm、632.8 nm、650.0 nm3种不同波长的激光照射白兰瓜种子,发现632.8 nm的激光处理可以极大的提高淀粉酶的含量和活力,并在48小时处淀粉酶同工酶有新的酶带出现,说明632.8 nm波长的激光能有效的激活白兰瓜种子萌发期的淀粉酶,加速物质和能量的代谢,提高种子的萌发活力.     

甜瓜下胚轴极性生根机理的研究Ⅲ腐胺对甜瓜下胚轴生根的效应

将甜瓜下胚轴接种在1/4MS固体培养基上能诱导其下端形成不定根.在生根过程中,内源腐胺含量增加了.腐胺合成抑制剂D-精氨酸抑制下胚轴中腐胺的合成,也抑制生根.在外加D-精氨酸的同时再添加腐胺提高下胚轴的生根率和根长到对照水平.以上结果表明,腐胺与甜瓜下胚轴生根密切有关.     

外源激素诱导甜瓜下胚轴愈伤组织的效应

在1/2MS的基本培养基中附加2,4-D1.0毫克/升、6-BA2.0毫克/升或2,4-D 0.1毫克/升和6-BA1.0毫克/升,都能诱导甜瓜下胚轴发生意伤组织。但是,不同激素作用下,甜瓜下胚轴愈伤组织的起源不同。2,4-D诱导维管束中薄壁细胞和紧靠维管束的一圈皮层细胞启动。6-BA诱导维管束中发生形成层以及诱导皮层细胞启动。不仅如此,2,4-D和6-BA对甜瓜下胚轴中可溶性蛋白的含量以及过氧化物酶活性影响也明显不同。在过氧化物同工酶谱的分析中发现附加6-BA时,形成的愈伤组织存在着特有的酶带。     

甜瓜果实特异性表达黄瓜素基因启动子区的克隆和序列分析

黄瓜素(cucum is in)是甜瓜类枯草杆菌丝氨酸蛋白酶,其表达具有果实特异性.应用PCR方法从甜瓜基因组DNA中扩增出该基因自转录起始位点至上游一段长310 bp片段,并将其克隆到pUC 19载体中,序列分析表明该序列与已报道的相应序列完全相同,且具有TATA-box、CAAT-box、G-box、I-box-like和增强子元件TGTCACA等功能域,具有典型的果实特异性启动子特征.成功获得甜瓜果实特异性表达基因的启动子,为下一步实现外源基因在甜瓜果实中特异表达奠定基础.     

甜瓜子叶发育过程中蛋白质水平和氨同化酶活性变化

测定了甜瓜种子萌发和子叶发育过程中谷氨酰胺合成酶(GS)、依赖于NADH的谷氨酸合酶(NADH-GOGAT)、依赖于NADH的谷氨酸脱氢酶(NADH-GDH)等酶的活性变化以及种子萌发时可溶性蛋白水平的变化．在有氮或无氮下，在子叶刚出土时GS和NADH-GOGAT活性较低，随着子叶的发育，这两种酶的活性升高，两者分别于第7天和第5天达到最高，其后活性逐步降低．但是NADH-GDH呈现出相反的变化，在子叶发育的前期阶段其活性低，而后逐步升高．可溶性蛋白的含量随着子叶的发育而逐步降低．外源氮的加入对蛋白质水平和酶的活性具有小的正面影响．     

转WMV-2CP基因甜瓜饲喂小鼠的安全性研究

转WMV-2CP基因甜瓜的小鼠急性和亚急性毒性试验、致突变试验以及30 d喂养安全性分析试验.其小鼠经口急性毒性半致死量LD50＞90 g/kg体重试验,表明该转基因食品属实际无急性毒性物质;微核实验和精子畸变实验及Ames实验均未发现有致突变作用;30 d喂养试验,54、108、162 g/kg体重各剂量组小鼠发育、...     

Properties and nucleotide sequence of linear plasmid-like DNA pC4 from mitochondria ofCucumis sativus

Four kinds of mitochondrial plasmid-like DNAs, designated pC1, pC2, pC3 and pC4, were detected in Cucumis sativus Jinyan No. 4. The electron microscopy observation showed that pC4 was linear conformation. Complete sequence of pC4 was cloned into pUC19 with E. coli JM109 as host. Sequence analysis revealed that pC4 was 370 bp long, the shortest one among all the reported mitochondrial plasmid-like DNAs. pC4 was AT rich. It contained terminal direct repeat sequence (35 bp in length)as well as many short direct and inverted repeats. ORFs in pC4 were short. pC4 was found to be homologous to nuclear DNAs, but lack homology with main mitochondrial and chloroplast DNAs. pC4-homologous sequence also occurred in nuclear genome of Jinyan No. 7 which contained no mitochondrial plasmid-like DNAs. The hybridization pattern of Jinyan No. 7 was slightly different from that of Jinyan No. 4. This suggested that pC4 occurred at the forepart of Cucumis sativus species divergence and integrated into the nuclear genome, and the pC4-homologous sequence in nucleus varied during species diverging.