Plant Physiology

Elthon, Thomas E.; McIntosh, Lee

doi: 10.1104/pp.82.1.1pmid: 16664973

Abstract The alternative oxidase activity of Sauromatum guttatum spadix mitochondria has been investigated as to its developmental expression and tissue localization. Mitochondria rich in alternative oxidase activity were found in a yellow cortex tissue present to varying degrees within the appendix, male floral, and sterile floral regions of the spadix. During a 5-day period just prior to anthesis, the alternative oxidase activity present in the appendix region was found to increase over 10-fold. On the following day when the appendix region becomes thermogenic, cytochrome oxidase activity was found to decrease by 92%, effectively forcing electron flow through the alternative oxidase. A procedure for efficient solubilization of the alternative oxidase from appendix region mitochondria was developed. The alternative oxidase thus solubilized was sensitive to heat inactivation and trypsin digestion. The activity showed inhibition characteristics expected of the alternative oxidase in that it was sensitive to salicylhydroxamic acid and 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole, but relatively insensitive to KCN and antimycin A. Essential sulfhydryl group(s) were indicated by reversible inhibition by p-chloromercuribenzoic acid. The solubilized alternative oxidase was most active in the detergent N,N-bis-(3-d-glucoamidopropyl)-deoxycholamide and had a pH optimum of 6.8. 1 Supported by National Science Foundation Postdoctoral Fellowship (T. E. E.) grant DMB-8508782 and Department of Energy contract DE-AC02-76ERO-1338. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Dale, Elizabeth MacDowell; Housley, Thomas Lee

doi: 10.1104/pp.82.1.7pmid: 16665025

Abstract Past research on kernel growth in wheat (Triticum aestivum) has shown that the kernel itself largely regulates the influx of sucrose for consequent starch synthesis in the endosperm of the grain. The first step in the conversion of sucrose to starch is catalyzed by sucrose synthase (EC 2.4.13). Sucrose synthase activity was assayed in developing endosperms from kernels differing in growth rate and in maximum dry weight accumulation. From 10 to 22 days after anthesis, sucrose synthase activity per wheat endosperm remained constant with respect to time in all grains. However, kernels which had higher rates of kernel growth and which achieved greatest maximum weight had consistently and significantly higher sucrose synthase activities at any point in time than did kernels with slower rates of dry matter accumulation and lower maximum weight. In addition, larger kernels had a significantly greater amount of water in which this activity could be expressed. Although the results do not implicate sucrose synthase as the “rate limiting” enzyme in wheat kernel growth, they do emphasize the importance of sucrose synthase activity in larger or more rapidly growing kernels, as compared to smaller slower growing kernels. 1 Supported in part by a grant from United States Department of Agriculture Competitive Research Grants Office, 59-2182-1-1-728, and by the Agriculture Experiment Station, Purdue University, AES Journal No. 10,434. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Wang, Shiow Y.; Sun, Tung; Faust, Miklos

doi: 10.1104/pp.82.1.11pmid: 16664976

Abstract The [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1- yl)-pentan-3-ol] (paclobutrazol, PP333) measured in apple seedlings (`York Imperial' Malus domestica Borkh) was confirmed by gas chromatography-mass spectrometry. Data showed that paclobutrazol was taken up through roots and transported primarily in the xylem through the stems and accumulated in leaves. No detectable basipetal movement of paclobutrazol in apple seedlings was found. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Sicher, Richard C.; Kremer, Diane F.; Harris, William G.

doi: 10.1104/pp.82.1.15pmid: 16664983

Abstract Levels of fructose 2,6-bisphosphate (F2,6BP) and related metabolites were measured in 8- or 9-day-old barley (Hordeum vulgare L.) primary leaves throughout a 24 hour cycle. Young barley leaves contained about 0.4 nanomole F2,6BP per milligram chlorophyll at the end of a 12 hour dark period. F2,6BP levels increased rapidly following a dark-to-light transition and then decreased to about 0.1 nanomole per milligram chlorophyll after 5 or 10 minutes of light. Low levels of F2,6BP were detected in barley primary leaves throughout the day. A 10-fold increase in F2,6BP was observed during the first hour of the dark period and then levels of this metabolite decreased slowly for the next several hours. Only small diurnal fluctuations were noted in barley leaf glucose 6-phosphate and uridine 5′-diphosphoglucose levels. There were rapid changes in whole leaf F2,6BP levels when the light intensity was altered. High F2,6BP levels in the dark were not observed after short photosynthetic periods. Results obtained with barley primary leaves support the suggestion that F2,6BP is involved in regulating the flow of photosynthate from the chloroplast to sucrose. Extractable sucrose-phosphate synthase activity was inversely related to barley primary leaf F2,6BP levels. This finding may indicate that the activities of sucrose-phosphate synthase and cytosolic fructose 1,6-bisphosphatase in barley primary leaves are metabolically coordinated. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Chia, Catherine P.; Duesing, John H.; Arntzen, Charles J.

doi: 10.1104/pp.82.1.19pmid: 16664990

Abstract Lutescens-1, a tobacco mutant with a maternally inherited dysfunction, displayed an unusual developmental phenotype. In vivo measurement of chlorophyll fluorescence revealed deterioration in photosystem II (PSII) function as leaves expanded. Analysis of thylakoid membrane proteins by polyacrylamide gel electrophoresis indicated the physical loss of nuclear- and chloroplast-encoded polypeptides comprising the PSII core complex concomitant with loss of activity. Freeze fracture electron micrographs of mutant thylakoids showed a reduced density, compared to wild type, of the EFs particles which have been shown previously to be the structural entity containing PSII core complexes and associated pigment-proteins. The selective loss of PSII cores from thylakoids resulted in a higher ratio of antenna chlorophyll to reaction centers and an altered 77 K chlorophyll fluorescence emission spectra; these data are interpreted to indicate functional isolation of light-harvesting chlorophyll a/b complexes in the absence of PSII centers. Examination of PSII reaction centers (which were present at lower levels in mutant membranes) by monitoring the light-dependent phosphorylation of PSII polypeptides and flash-induced O2 evolution patterns demonstrated that the PSII cores which were assembled in mutant thylakoids were functionally identical to those of wild type. We conclude that the lutescens-1 mutation affected the correct stoichiometry of PSII centers, in relation to other membrane constituents, by disrupting the proper assembly and maintenance of PSII complexes in lutescens-1 thylakoid membranes. 2 Current address: Biology Department, Princeton University, Princeton, NJ 08544. 3 Current address: Biotechnology Research, CIBA-GEIGY Corp., P. O. Box 12257, Research Triangle Park, NC 27709-2257. 1 Supported, in part, by Department of Energy Contract No. DE-AC02-76ERO-1338 to Michigan State University and a grant from E. I. du Pont de Nemours, Inc. C. P. C. received partial support from a United States Office of Education Graduate and Professionals Opportunities Program Fellowship. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Holmes, M. Geoffrey; Klein, William H.

doi: 10.1104/pp.82.1.28pmid: 16665006

Abstract Stomatal diffusion resistance in primary leaves of Phaseolus vulgaris L. which had been grown in light:dark cycles followed a marked circadian rhythm when the plants were transferred to continuous darkness. Reentrainment of the rhythm required more than one inductive change in photoperiod. The phasing of the rhythm of dark stomatal opening was contolled primarily by the light-on (dawn) signal, whereas the rhythm of dark closure was related to the light-off (dusk) signal. The evidence points to a dual control of the circadian clock in which a product of photosynthesis plays a major role. No evidence for phytochrome involvement in the phasing of the rhythm was found. An influence of phytochrome on the amplitude of the stomatal rhythm was observed in which removal of phytochrome-far-red absorbing form caused rapid damping. 1 Present address: M. G. Holmes, (Botany School, University of Cambridge, Downing Street, Cambridge CB2 3EA, U.K.) This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Reeves, Christopher D.; Krishnan, Hari B.; Okita, Thomas W.

doi: 10.1104/pp.82.1.34pmid: 16665020

Abstract The developmental accumulation pattern of messenger RNA transcripts and polypeptides for wheat gliadins and ADPglucose pyrophosphorylase was determined using cDNA and antibody probes. Gliadin mRNA was detected on Northern and RNA dot blots at 3 days after flowering, it increased 100-fold by 10 days and decreased subsequent to 14 days. The abundant mRNAs encoding α/β- and γ-type gliadins and mRNA for ADPglucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis, accumulated coordinately. Despite the coordinate accumulation of their mRNA transcripts, the accumulation of gliadin and ADPglucose pyrophosphorylase polypeptides, as determined by Western blot, differed significantly. The time at which gliadin and ADPglucose pyrophosphorylase mRNAs began accumulating was also the time when the overall pattern of gene expression, as seen by two-dimensional gel electrophoresis of in vitro translation products, changed most significantly. However, the accumulation of a number of other mRNAs or polypeptides having unknown function occurred at other times during endosperm development. The pattern of expression in the earliest stages of development was strikingly similar to that of coleoptile, another rapidly growing, nonphotosynthetic tissue. Thus, the pattern of gene expression reflects the program of development observed cytologically. 1 Supported by Grants PCM-8215772 and DCB-8502244 from the National Science Foundation. Scientific paper No. 7041, Project 0590, of the College of Agriculture Research Center, Washington State University. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Rickauer, Martina; Tanner, Widmar

doi: 10.1104/pp.82.1.41pmid: 16665021

Abstract Ca2+ stimulates the uptake of α-aminoisobutyric acid (AIB) into excised or intact Phaseolus vulgaris L. roots by a factor of two. In roots depleted of Ca2+ by preincubation with ethylenediaminetetraacetate, ethyleneglycol-bis(β-aminoethyl ether)-N,N′-tetraacetic acid, or streptomycin, the stimulatory effect is 7- to 10-fold. In the presence of Ca2+, roots accumulate AIB more than 100-fold; Ca2+-depleted roots only equilibrate with AIB. Radioautography shows [14C]AIB to be present in all cells after 90 min. Although Ca2+-depleted roots lose accumulated [14C]AIB about 10 times faster than roots supplied with Ca2+, this increased efflux is not the main cause for the decrease in net uptake observed. The latter is rather due to a less negative membrane potential Δψ in Ca2+ depleted roots (−120 mV → −50 mV). The basic feature explaining all the results of Ca2+ deficiency is an increase in general membrane permeability. No indication of a specific regulatory function of Ca2+ in membrane transport of roots has been obtained. 1 Supported by the “Deutsche Forschungsgemeinschaft” (SFB 43). This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Lew, Roger R.; Briskin, Donald P.; Wyse, Roger E.

doi: 10.1104/pp.82.1.47pmid: 16665022

Abstract Ca2+ uptake into microsomal vesicles was measured using the fluorescent probe chlorotetracycline. The Ca2+ uptake was ATP-dependent and did not occur in the presence of the calcium ionophore A23187. There was a linear relationship between the rate of ATP-dependent fluorescence increase using chlorotetracycline and ATP-dependent 45Ca2+ uptake, indicating that chlorotetracycline can be used as a quantitative probe for Ca2+ uptake. The fluorescent probe allows measurements to be made in real time, and avoids the use of radioisotopes. Ca2+ transport was associated with endoplasmic reticulum on linear gradients when the endoplasmic reticulum was in either rough or smooth form. The Ca2+ uptake had a pH optimum of 7.5, a K m for ATP of 0.1 millimolar, a K m for Ca2+ of about 70 nanomolar, and was stimulated 2-fold by calmodulin. Vanadate inhibited uptake completely at a concentration of 50 micromolar, half-maximally at 5 micromolar. Carbonyl cyanide 4-(trifluoromethoxy)-phenyl-hydrazone, oligomycin, azide, and nitrate caused only slight inhibition. Dicyclohexylcarbodiimide (DCCD) stimulated slightly at concentrations as high as 400 micromolar. The hormones gibberellic acid, indoleacetic acid, and abscisic acid at 10 micromolar had no significant effect. Myo-inositol 1,4,5-trisphosphate did not cause release of Ca2+ after uptake. The properties of the enzyme suggest that it has a functional role in regulating cytosolic Ca2+ levels. Based on the lack of an effect by hormones, it may not act as a mediator of second messenger roles of Ca2+. The inhibition by vanadate and slight stimulation by DCCD may be useful as a `signature' for this endoplasmic reticulum Ca2+ uptake system. 2 Present address: Department of Physiology, Yale University School of Medicine, P.O. Box 3333, B-106 SHM, New Haven, CT 06510-8026. 3 Present address: Department of Agronomy, University of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801. 4 Present address: New Jersey Agricultural Experiment Station, Rutgers University, Cook College, Martin Hall, New Brunswick NJ 08903. 1 Cooperative research of the United States Department of Agriculture, Agricultural Research Service and the Utah Agricultural Experiment Station. Published as Utah Agricultural Experiment Station Journal Article No. 3147. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Tolley-Henry, Leslie; Raper, C. David

doi: 10.1104/pp.82.1.54pmid: 11539090

Abstract Dry matter accumulation of plants utilizing NH4+ as the sole nitrogen source generally is less than that of plants receiving NO3− unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4+ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4+ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 ± 0.1 by automatic additions of 0.01 n H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4+ uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4+ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4+, which were initially about 50% lower at pH 4.1 than at 6.1, continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis. 2 L. T.-H. was supported by a R. J. Reynolds Postdoctorate Fellowship. 1 Supported in part by National Aeronautics and Space Administration grant NCC 2-101. Paper No. 10295 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. This content is only available as a PDF. © 1986 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)