摘要:

The exact subcellular location of sucrose synthase (UDP-d-glucose:d-fructose 2-α-d-glucosyltransferase, EC2.4.1.13) inHelianthus tuberosustubers was studied by comparison of its activity in protoplasts with that of vacuoles isolated from them. Assuming 100% of theβ-N-acetylglucosaminidase activity to be of vacuolar origin, less than 5% of both the sucrose synthase activity and the extravacuolar marker NAD-malate dehydrogenase was detected in the vacuole preparations. Sucrose synthase is therefore an extravacuolar enzyme. Its role in the inulin metabolism ofH. tuberosusis discusse

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

In etiolated squash (Cucurbita maximaL.) cotyledons, nitrate-inducible NADH:nitrate reductase activity and protein were increased in darkness by red light pulses with red/far-red photoreversibility. Continuous far-red light also led to increased levels of nitrate reductase activity and protein. Poly(A)+RNA, which hybridizes to squash nitrate reductase cDNA, was also increased by light treatments. Thus, we found that after nitrate triggering, nitrate reductase expression appears to be regulated by light via phytochrome.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

Cytokinin oxidase activity fromPhaseolus vulgariscv Great Northern callus cultures exhibited affinity for the lectin concanavalin A. Over 80% of the activity extracted from the callus tissue bound to a concanavalin A-Sepharose 4B column. The bound activity was eluted from the column by the addition of methylmannose to the eluting buffer. On the basis of this result, it appears that most of the cyokinin oxidase activity present in Great Northern callus cultures exists in the form of a glycoprotein. The apparent pI of this enzyme, as estimated by chromatofocusing, is approximately 5.0.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

We have examined the activity of the thiamin phosphate pyrophosphorylase inArabidopsis thalianawild type and in a mutant (th-1) which requires exogenous thiamin for growth. Mutant and wild-type plants grown in 1×10−7molar thiamin were used for the examination of the production of thiamin and thiamin monophosphate (TMP) using 4-methyl-5-hydroxyethylthiazole phosphate and 2-methyl-4-amino-5-hydroxymethylpyrimidine pyrophosphate as substrates. While the wild-type strain formed both thiamin and TMP, theth-1mutant did not. When TMP was added to the extracts, theth-1mutant, as well as wild type, produced thiamin. Accordingly, it was concluded that theth-1mutant was defective in the activity of TMP pyrophosphorylase. Some of the characteristics of the enzyme from the wild-type plant were examined. The optimum temperature for the reaction is 45°C, and theKmvalues for the substrates are 2.7×10−6molar for 4-methyl-5-hydroxyethylthiazole phosphate and 1.8×10−6molar for 2-methyl-4-amino-5-hydroxymethylpyrimidine pyro

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

The mechanism of sucrose transport into vacuoles isolated from leaf tissue has been studied only in barley (Hordeum vulgare) mesophyll cells. In this tissue, sucrose transport was reported to be a facilitated diffusion. We have observed a facilitated diffusion of sucrose into vacuoles isolated from this tissue. However, no pH dependence was observed. Evidence is presented indicating that the pH dependence of sucrose uptake into vacuoles may be an artifact, reflecting tonoplast instability and survival of isolated vacuoles in different buffers. Apparently vacuoles do not withstand exposure to some commonly used buffers.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

Rye (Secale cerealecv Halo) seedlings treated with the herbicide Norflurazon SAN 9789 showed a reduced concentration of mRNA for the small subunit of ribulose-1,5-bisphosphate carboxylase and for the light-harvesting chlorophylla/bprotein. The inhibition of mRNA accumulation by Norflurazon occurred only in the presence of high light intensities and only after a period of days. The primary effect was an inhibition of the transcription rate that occurred within 1 day after exposure of the seedlings to light.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

Isolated sugarcane (Saccharumspp. hybrid H50-7209) vacuoles incorporate radioactivity during incubation with labeled UDP-glucose by a mechanism which was postulated to be responsible for sucrose storage in the vacuoles (UDP-glucose group translocator). Analysis of the reaction products in the medium revealed that several enzymic processes are going on during incubation with UDP-glucose such as production of hexose phosphates, UMP, and sugars, all of which seem unrelated to the incorporation of radioactivity into vacuoles. The incorporated radioactivity was identified mainly as (1→3)-β-glucan (callose) of polymerization grades up to more than 20. Callose occurs as a contaminant at the surface of isolated vacuoles coming from the plasmalemma. The properties of UDP-glucose incorporation into the vacuolar preparation compared favorably with known properties of callose synthase. The low mol wt glucans that are found are probably degradation products of labeled callose due to hydrolases, which are liberated by centrifugation of vacuoles. The labeled disaccharide, which chromatographically had been formerly identified as sucrose, is laminaribiose. No sucrose (or sucrose phosphate) could be identified in the vacuole preparation after incubation with UDP-glucose. Thus, the mechanism of sucrose storage in sugarcane vacuoles is still op

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

A reanalysis of products formed after short-term incubation of sugarcane (Saccharumspp. hybrid cv H50-7209) vacuole preparations with uridine diphosphate [14C]glucose was performed. The results indicated that the ethanol-soluble substance previously identified as sucrose did not elute with sucrose when subjected to high performance liquid chromatography but had the same retention time as a disaccharide tentatively identified as laminaribiose.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

To isolate chitinases andβ-1,3-glucanases from the intercellular space of oats (Avena sativaL.), primary leaves were infiltrated with buffer and subjected to gentle centrifugation to obtain intercellular washing fluid (IWF). Approximately 5% of the chitinase and 10% of theβ-1,3-glucanase activity of the whole leaf were released. Only small amounts (0.01-0.03%) of the intracellular marker malate-dehydrogenase were released into the IWF during infiltration. Activities of chitinase andβ-1,3-glucanase in the IWF and in the leaf extract were compared by different chromatographic methods. On Sephadex G-75, chitinase appeared as a single peak (Mr29.8 kD) both in IWF and homogenate.β-1,3-Glucanase, however, showed two peaks in the IWF (Mr52 and 31.3 kD), whereas the elution pattern of the homogenate showed only one major peak at 22 kD. Chromatofocusing indicated that the IWF contained four chitinases and fiveβ-1,3-glucanases. The elution pattern of the homogenate and IWF were similar with regard to the elution pH, but the peak intensities were distinctly different. Our results demonstrate that extracellularβ-1,3-glucanases are different from those located intracellularly. Extracellular and intracellular chitinases do not differ in molecular properties, except for one isozyme which seems to be confined to the extracellular space. We suggest that both enzymes might play a special role in pathogenesis during fungal infe

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB

摘要:

Germination ofKalanchoëblossfeldianaPoelln. seeds is absolutely light-requiring. Germination of one seed is the result of one out of three reactions,viz.the very low fluence response (VLFR), the low fluence response (LFR) and the high fluence response/high irradiance response. In order to demonstrate the involvement of phytochrome for both photoresponses,i.e.VLFR and LFR, action spectra for induction were determined. Fluence-response data are analyzed by means of probit analysis in order to calculate the seed population parameters, with special attention toμ, or the fluence for half-maximal induction, andB, the slope in the probit diagram. Laser light was used between 620 and 800 nanometers to analyze the VLFR. Phytochrome is responsible for both photoresponses: the VLFR action spectrum demonstrates an exponential decrease in apparent photoconversion cross-section (Pr→Pfr) up to about 800 nanometers. Assuming that Pr:Pfr-Xand Pfr:Pfr-Xare the effectors for the VLFR and the LFR, respectively, we estimate an average induction threshold of about 0.003% Pr:Pfrfor the VLFR and about 1% Pfr:Pfrfor the LFR among individuals of the seed populat

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1988

数据来源: ASPB