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101.
It is known that low root zone temperatures (RZT) have moreeffect on infection and early nodule development than on nitrogenfixation by soybean [Glycine max (L.) Merr.]. However, therehave been no studies regarding how the low RZT inhibit the infectionstages of soybean. Two controlled environment experiments wereconducted to examine the effect of low RZT on bacterial attachmentto, and infection thread penetration of, soybean root hairs.The experimental designs were (1) plants maintained at 25, 17.5or 15C RZT, or transferred from 25 or 17.5 to 15C RZT at either0.5, 1, 2, or 7d after inoculation (DAI), (2) early symbioticestablishment between soybean and Bradyrhizobium japonicum wasexamined microscopically under three RZT (15, 17.5 and 25C).These results indicated that (1) keeping plants at 25C only0.5 DAI prior to transfer to a 15C RZT accelerates the onsetof N2 fixation at 15C RZT by 6 d, (2) at RZT between 25 and17.5C the infection processes were progressively delayed astemperature declined, (3) RZT less than 17C strongly inhibitedinfection steps, such that when RZT dropped 8.5C from 25 to17.5C infection initiation was delayed 1 d, while when RZTdropped only 2.5C from 17.5 to 15C, infection initiation wasdelayed another 2 d. Key words: Bradyrhizobium japonicum, low temperature, nodulation, soybean 相似文献
102.
Kelem Kassahun Pei Hu Mark P. Grillo Margaret R. Davis Lixia Jin Thomas A. Baillie 《Chemico-biological interactions》1994,90(3):253-275
The ability of 2-n-propyl-4-pentenoic acid (Δ4-VPA) and 2-n-propyl-2(E)-pentenoic acid ([E]-Δ2-VPA), two unsaturated metabolites of valproic acid (VPA), to form reactive intermediates, deplete hepatic glutathione (GSH) and cause accumulation of liver triglycerides was investigated in the rat. With the aid of ionspray liquid chromatography-tandem mass spectrometry (LC-MS/MS), three GSH adducts were detected in the bile of Δ4-VPA-treated animals and were identified as 4-hydroxy-5-glutathion-S-yl-VPA-γ-lactone, 5-glutathion-S-yl-(E)-Δ3-VPA and 3-oxo-5-glutathion-S-yl-VPA. A fourth conjugate was identified tentatively as 4-glutathion-S-yl-5-hydroxy-VPA. Quantitative analysis of the corresponding N-acetylcysteine (NAC) conjugates in urine indicated that metabolism of Δ4-VPA via the GSH-dependent pathways accounted for approximately 20% of an acute dose (100 mg kg−1 i.p.). In contrast, when rats were given an equivalent dose of (E)-Δ2-VPA, only one GSH adduct (5-glutathion-S-yl-(E)-Δ3-VPA) was detected at low concentrations in bile. In vitro experiments with rat liver mitochondria demonstrated that Δ4-VPA undergoes coenzyme A- and ATP-dependent metabolic activation in this organelle via the β-oxidation pathway to intermediates which bind covalently to proteins. When liver homogenates and hepatic mitochondria from rats injected with Δ4-VPA, (E)-Δ2-VPA or VPA were analyzed for GSH content, it was found that only Δ4-VPA depleted GSH pools significantly. Treatment of rats with Δ4-VPA and (to a lesser extent) VPA led to an accumulation of liver triglycerides, whereas (E)-Δ2-VPA had no measurable effect. It is concluded that Δ4-VPA undergoes metabolic activation by both microsomal cytochrome P-450-dependent and mitochondrial coenzyme A-dependent processes, and that the resulting electrophilic intermediates, which are trapped in part by GSH, may mediate the hepatotoxic effects of this compound. In contrast, (E)-Δ2-VPA is not transformed to any appreciable extent to reactive metabolites, which thus accounts for the apparent lack of hepatotoxicity of this positional isomer in the rat. 相似文献
103.
Insect resistance of transgenic plants that express modified Bacillus thuringiensis cryIA(b) and cryIC genes: a resistance management strategy 总被引:7,自引:0,他引:7
104.
Expression of mouse metallothionein-I gene confers cadmium resistance in transgenic tobacco plants 总被引:8,自引:0,他引:8
Aihua Pan Meizhu Yang Feng Tie Lingyua Li Zhangliang Chen Biggen Ru 《Plant molecular biology》1994,24(2):341-351
Transgenic tobacco plants containing a mouse metallothionein-I (MT-I) gene fused to the cauliflower mosaic virus 35S (CaMV 35S) promoter and nopaline synthase (nos) polyadenylation site were obtained by transforming tobacco leaf discs with an Agrobacterium tumefaciens strain carrying the chimaeric gene. Transformants were directly selected and rooted on medium containing cadmium and kanamycin. A total of 49 individual transgenic tobacco plants were regenerated. Among them 20% showed a very high expression level and their growth was unaffected by up to 200 M cadmium, whereas the growth of control plants was severely affected leaf chlorosis occurred on medium containing only 10 M cadmium. The concentration of MT-I in leaves of control and transgenic tobacco was determined with Cd/haemoglobin saturation assay, a polarographic method and western blotting. In addition, seeds from self-fertilized transgenic plants were germinated on medium containing toxic levels of cadmium and scored for tolerance/susceptibility to this heavy metal. The ratio of tolerant to susceptible plants was 3:1 indicating that the metallothionein gene is inherited as a single locus. 相似文献
105.
Jin Feng Kunitoshi Yamanaka Hironori Niki Teru Ogura Sota Hiraga 《Molecular & general genetics : MGG》1994,243(2):136-147
The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA
+ gene were grown at 30° C and then transferred to 42° C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB
+ plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42° C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid. 相似文献
106.
河南叶县下寒武统辛集组单板类和腹足类化石的研究 总被引:8,自引:3,他引:5
本文描述和讨论了河南叶县杨寺庄下寒武统辛集组单板类13种,腹足类2种,未定类1种。其中包括2新属6新种:Repenoconus xinjiensis gen.nov.,Scenella pycna sp.nov.,Securiconus vulgaris sp.nov.,Obtusocnus grossicostus sp.nov.,Igorellina proboscis sp.nov.,Gal 相似文献
107.
卡拉胶固定粘质赛氏菌产碱性蛋白酶的研究 总被引:4,自引:0,他引:4
将粘质赛氏菌(Seratia marcescens)包埋于卡拉胶中,发现2.5%的卡拉胶适于固定该菌产碱性蛋白酶。固定化细胞在其较适宜产酶培养基中发酵,酶活力一般可达400u/ml,在卡拉胶中添加3%玉米粉和1%豆饼粉或2%砂子制备固定化细胞,其产酶能力分别提高了25%和23.9%;固定化细胞颗粒越小,其产酶能力越高。采用摇瓶半连续发酵。其产酶半衰期为14次(24小时为一个周期);而用环流器进行半连续发酵,其产酶半衰期为52次(12小时为一个周期),产酶效率分别比游离细胞摇瓶发酵的产酶效率高11.8%和45.07%,而环流器半连续发酵的产酶效率比摇瓶半连续发酵高29.7%。 相似文献
108.
109.
Largepterosaurwithamaximumwingspanofmorethan5metres.Theskullislowerandlonger,withoutmiddlecrestorsupraoccipita1crest.ThenasaIandpre-orbita1fenestraareconfluentcompletely,andoccupyaboutha1foftheskulI1ength.Thetoothlessbeakisslenderandpointed.The1ongneckiscomposedbyse-venslendercervicalvertebrae.Thenotariumconsistsofsixco-ossifiedanteriordorsalvertebrae-ThetaiIisextremlyshort.lthassixpairsof"A"shapegastralia.Theanteriorlimbsarestrong;thehumerusarethickandshort;thewing-metacarpalbonearelongert… 相似文献
110.