摘要:

α-Amylase has been purified from de-embryonated seeds of barley (Hordeum vulgareL. cv. Betzes) which have been incubated on 10−6mgibberellic acid (GA3) following 3 days of imbibition in buffer. Incubation of the half-seeds in up to 10−2m5-fluorouracil (5-FU) during the entire incubation period, including imbibition, had no effect on any of the following characteristics of purifiedα-amylase: thermal stability in the absence of calcium, molecular weight of the enzyme, isozyme composition, specific activity, or the amount ofα-amylase synthesized by the aleurone tissue. The synthesis of rRNA and tRNA was strongly inhibited by 5-FU, indicating that the analog had entered the aleurone cells. These results are not in agreement with those of Carlson (Nature New Biology 237: 39-41 [1972]) who found that treatment of barley aleurone with 10−4m5-FU prior to the addition of GA3resulted in decreased thermal stability of GA3-inducedα-amylase and who interpreted this as evidence that the mRNA forα-amylase was synthesized during the imbibition of the aleurone tissue and independently of gibberellin action. Results of the present experiments indicate that the thermal stability of highly purifiedα-amylase is not altered by treatment of barley half-seeds with 5-FU, and that 5-FU cannot be used as a probe to examine the timing ofα-amylase mR

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

We examined cell length, mitosis, and root meristem“cuticle”in different tissues of geostimulated, red light-exposed primary roots of corn (Zea Mays, Wisconsin hybrid 64A×22R). The examination was done at 15-minute intervals for a period of 240 minutes. Differences in cell elongation between the upper and lower sides were most prominent between 1.5 and 2.5 mm from the root meristem; the outer cortex had the greatest elongation growth, and the upper cells showed a significant increase in length compared to the lower. A differential mitosis was also found, with the lower tissue being greater. We infer that the mitotic activity is indicative of cell division, and this division occurs strictly in the first 1.5 mm of the root meristem. The combined effect of differential cell elongation and cell division results in the localization of the geotropic curvature in the 1.5- to 2.5-mm region from the root meristem. Mitosis that occurs primarily in the cortex and stele were asynchronous; the peak of cortical division preceded that of the stele. Both peaks occurred before the peak of geotropism. A densely stained layer separates the cap from the root meristem. This layer is thinner at the apex of the root meristem. The area of the thin region increased with time and peaked at 180 minutes after geostimulation, which was coincidental with the peak of the geotropic resp

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Of the total protein in the protein bodies of castor bean (Ricinus communisL.), approximately 40% is represented by a group of closely related albumins localized in the matrix of the organelle. This group of albumins has a sedimentation value of 2S and is resolved into several proteins of molecular weight around 12,000 daltons by sodium dodecyl sulfate-acrylamide gel electrophoresis. It has a high content of glutamate/glutamine and undergoes rapid degradation during the early stage of germination. In view of the abundance and ubiquitous occurrence of albumins in various seeds, we suggest that albumins, in addition to globulins, glutelins, and prolamines, are important storage proteins in seeds.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Germination ofAmaranthus retroflexusL. seeds imbibed at 40 C is enhanced by establishing the active form of phytochrome before a reduction in temperature to32 C by a transition in the plasmalemma.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Leucine:tRNA ligase was assayed in extracts from cultured tobacco (Nicotiana tabacum) XD cells by measuring the initial rate of aminoacylation of transfer RNA withl-[4,5-3H]leucine. Transfer RNA was purified from tobacco XD cells after the method of Vanderhoefet al.(Phytochemistry 9: 2291-2304). The buoyant density of leucine:tRNA ligase from cells grown for 100 generations in 2.5 mm[15N]nitrate and 30% deuterium oxide was 1.3397. After transfer of cells into light medium (2.5 mm[14N]nitrate and 100% H2O) the ligase activity increased and the buoyant density decreased with time to 1.3174 at 72 hours after transfer. It was concluded that leucine:tRNA ligase molecules were synthesizedde novofrom light amino acids during the period of activity increase. The width at half-peak height of the enzyme distribution profiles following isopycnic equilibrium centrifugation in caesium chloride remained constant at all times after transfer into light medium providing evidence for the loss of preexisting functional ligase molecules. It was concluded that during the period of activity increase the cellular level of enzyme activity was determined by a balance betweende novosynthesis and the loss of functional enzyme molecules due to either inactivation or degradation.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

This paper reports the purification and structural determination of the mannolipid shown previously (Ericson and Delmer 1977 Plant Physiol 59: 341-347) to serve as an intermediate in glycoprotein synthesis in cotyledons ofPhaseolus vulgaris.The mannolipid was purified by chromatography in organic solvents on diethylaminoethyl-cellulose, followed by repeated steps of deacylation and rechromatography on Sephadex LH-20. Binding and elution behavior on diethylaminoethyl-cellulose was consistent with the presence of a monophosphate residue. Lability of the mannolipid to mild acid treatment as well as its resistance to hot phenol treatment or catalytic hydrogenation are consistent with the structure of a polyprenol having a saturatedα-residue. After methanolysis, the chloroform-methanol-soluble portion of the mannolipid was analyzed by mass spectrometry. The fragmentation pattern obtained was nearly identical to that obtained from standard dolichol-phosphate. An intense ion at m/e 69 represented theω-terminal isoprenoid residue, and repeating fragments separated by 68 mass units were observed up to m/e of>1,200. All evidence supports the conclusion that the mannolipid is dolichol-monophosphate-mannose and thus provides further support for the concept that the processes involved in the glycosylation of protein in higher plants are similar to those known to occur in the animal kingdo

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Specific antisera were prepared against the Bowman-Birk trypsin inhibitor and four other trypsin inhibitors of low molecular weight isolated from soybeans (Glycine maxL. cv. Tracy). These antisera were used to detect the presence and amount of the inhibitors in: (a) seeds and protein extracts of soybean meal; (b) seedlings; and (c) the water surrounding the seeds and roots of seedlings. Lectin activities in seeds, seedlings, and water were also determined at the same time as the protease inhibitor activities. By competitive inhibition of immunoprecipitation, the combined five low molecular weight protease inhibitors were found to constitute the following percentages of proteins (w/w): 6.3% in defatted soybean meal; 8.1% of the protein extracted from the meal by a buffer of pH 8.6; 8.3, 14.7, 15.2, 16.1, 17.2, and 18.9% of the protein in a lyophilisate of water in which seeds were incubated for 4, 8, 12, 16, 20, and 24 hours, respectively; 8.2% in a lyophilisate of water in which roots of seedlings grew for 20 days; 1.5% in cotyledons; and less than 0.1% in epicotyls, hypocotyls, and roots of 12-day-old seedlings. Hemagglutination activities, expressed as the lowest amount of protein required to give a positive agglutination of 0.2 ml of 2% rabbit red blood cells, were as follows: purified soybean lectin, 0.08μg; lyophilisate of water in which seeds were incubated for 4, 8, 12, 16, 20, and 24 hours, 10, 2.5, 5, 5, and 2.5μg, respectively; lyophilisate of water in which roots grew for 20 days, 5μg; 12-day-old cotyledons, roots, epicotyls, and hypocotyls, 12.5, 100,>1,000, and>500μg, respectively. The results indicate that a large amount of protease inhibitors as well as lectins are released from seeds during the first 8 hours of imbibition. Neither lima bean trypsin inhibitor (mol wt, 10,000) nor Kunitz soybean trypsin inhibitor (mol wt, 21,500) showed competitive inhibition in tests with antisera against low molecular weight soybean protease inhibit

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Osmotic regulation in the flagellateOchromonas malhamensisPringsheim is mainly mediated by changes in the pool size ofα-galactosyl-(1→1)-glycerol (isofloridoside). Isofloridoside phosphate synthase, a regulated key enzyme responsible for the formation of isofloridoside phosphate, appears to exist as an inactive proenzyme which can be activated by incubation of crude cell extracts with endogenous or exogenous proteas

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

Evidence has been obtained for the presence in filtrates of 3-day-old cultures of the fungusRhizopus stolonifergrown on potato-dextrose medium of both high molecular weight and low molecular weight elicitors of the production of the phytoalexin casbene in cell-free extracts of castor bean (Ricinus communisL.) seedlings. The high molecular weight elicitor activity was purified by means of gel filtration chromatography. Both protein and carbohydrate are associated with the most purified fraction containing elicitor activity. The elicitor is inactivated by treatments at 60 C or higher temperatures for 15 minutes. The molecular weight of the purified elicitor was estimated from gel filtration chromatography in 10 mmNa-phosphate (pH 7) to be 30,000±5,000. Treatments of the purified elicitor fraction with either sodium periodate or the nonspecific protease preparation, pronase, substantially reduced its activity as an elicitor of casbene production. On the basis of these properties it is concluded that the elicitor is most likely a protein and may be a glycoprotein. It is estimated that 2×10−8melicitor gives about a 14-fold increase in casbene synthetase activity in extracts of treated split seedlings in comparison with controls. This corresponds to about 50% of the maximal activity obtainable in this assay system developed to measure elicitor activ

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB

摘要:

A novel compound, serinol phosphate, was identified in sugarcane (Saccharum officinarum) clone 51NG97. It was produced by an enzyme-mediated transamination of dihydroxyacetone phosphate with either alanine, glutamate, aspartate, or glutamine serving equally well as an amino donor. Some detectable phosphatase activity was present in crude leaf enzyme preparation that hydrolyzed serinol phosphate. A proposal for a pathway of the biosynthesis of serinol in sugarcane was formulated.Serinol can serve as an“activator”of toxin production in attenuated cultures of the sugarcane pathogenHelminthosporium sacchariand it is present in susceptible clone 51NG97. Resistant clone H50-7209 does not possess serinol and likewise no dihydroxyacetone phosphate transaminase activity could be demonstrated in enzyme preparations of this clone. The concept of toxin activation in attenuated fungus cultures is briefly discussed relative to disease resistance and susceptibil

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1978

数据来源: ASPB