Plant Physiology

Singh, Bijay K.; Lonergan, Scott G.; Conn, Eric E.

doi: 10.1104/pp.81.3.717pmid: 16664890

Abstract The isoenzyme pattern of chorismate mutase (EC 5.4.99.5) was examined by diethylaminoethyl-cellulose chromatography in a wide variety of plants. All plants contained a regulated form of chorismate mutase (CM-1), and most contained an additional, unregulated form (CM-2). The regulatory properties of CM-1 differed significantly between plants. Antisera prepared against CM-1 and CM-2 from Sorghum bicolor were used to test immunological cross reaction of chorismate mutases from other plants. There was a high degree of similarity between chorismate mutase isoenzymes from Sorghum bicolor and Zea mays and some with Hordeum vulgare, but all other species studied were antigenically distinct from sorghum. No homology between the structure of CM-1 and CM-2 was detected within any species. 1 Supported in part by United States Public Health Service grant GM-05301-28. 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)

Yandow, Tim S.; Klein, Richard M.

doi: 10.1104/pp.81.3.723pmid: 16664891

Abstract Nitrate reductase activity (NRA) was found in primary roots, but not in foliage of red spruce (Picea rubens Sarg.) seedlings. Nitrate induced NRA:NH4+ did not induce and slightly depressed NRA in older seedlings. Induction required 8 hours and, once induced, NRA decreased slowly in the absence of exogenous NO3−. Seedlings were grown in perlite with a complete nutrient solution containing NH4+ to limit NR induction. Established seedlings were stressed with nutrient solutions at pH 3, 4, or 5 supplemented with Cl− salts of Al, Cd, Pb, or Zn each at two concentrations. NRA in primary root tips was measured at 2, 14, 28, and 42 days. NRA induction was greatest at pH 3, and remained high during the period of study. NRA induction at pH 4 was lower. Metal ions suppressed NRA at pH 3 and 5, but enhanced NRA at pH 4. It is concluded that acidity and soluble metals in the root environment of red spruce are unlikely to be important factors in nitrogen transformations in red spruce roots. 1 Supported by the R. K. Mellon Foundation, the Jackson Hole Foundation, the Texaco Foundation, and the American Electric Power Service Corp. Journal paper 593 from the Vermont Agricultural Experiment Station. 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)

Horwitz, Benjamin A.; Trad, Chafia H.; Lipson, Edward D.

doi: 10.1104/pp.81.3.726pmid: 16664892

Abstract A brief pulse of blue light induces the common soil fungus Trichoderma harzianum to sporulate. Photoresponse mutants with higher light requirements than the wild type are available, including one class, dim Y, with modified absorption spectra. We found blue-light-induced absorbance changes in the blue region of the spectrum, in wild-type and dim Y mutant strains. The light-minus-dark difference spectra of the wild type and of several other strains indicate photoreduction of flavins and cytochromes, as reported for other fungi and plants. The difference spectra in strains with normal photoinduced sporulation have a prominent peak at 440 nm. After actinic irradiation, this 440 nanometer difference peak decays rapidly in the dark. In two dim Y photoresponse mutants, the difference spectra were modified; in one of these, LS44, the 440 nanometer peak was undetectable in difference spectra. Detailed study of the dark-decay kinetics in LS44 and the corresponding control indicated that the 440 nanometer difference peak escaped detection in LS44 because it decays faster than in the control. The action spectrum of the 440 nm difference peak is quite different from that of photoinduced sporulation. The light-induced absorbance changes are thus unlikely to be identical to the primary photochemical reaction triggering sporulation. Nevertheless, these results constitute genetic evidence that physiologically relevant pigments participate in these light-induced absorbance changes in Trichoderma. 2 Present address: Carnegie Institution of Washington, Department of Plant Biology, 290 Panama St., Stanford, CA 94305-1297. 1 Supported by National Science Foundation grant DMB-8316458 to E.D.L. B.A.H. was supported by a Weizmann Postdoctoral 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)

Norman, Helen A.; John, Judith B. St.

doi: 10.1104/pp.81.3.731pmid: 16664893

Abstract Synthesis of unsaturated monogalactosyldiacylglycerol (MGDG) was examined in a mutant of Arabidopsis thaliana (L.) Heynh. containing reduced levels of hexadecatrienoic (16:3) and linolenic (18:3) acids in leaf lipids. Molecular species composition and labeling kinetics following the incorporation of exogenous [14C]fatty acids suggest that at least two pathways and multiple substrates are involved in desaturation of linoleic acid (18:2) to 18:3 for production of unsaturated galactolipids. A reduction in 18:3/16:3 MGDG and an increase in 18:2/16:2 MGDG, together with labeling kinetics of these molecular species following the incorporation of exogenous [14C]12:0 fatty acids, suggests that a chloroplastic pathway for production of 18:3 at the sn-1 position of MGDG utilizes 18:2/16:2 MGDG as a substrate. This chloroplastic (prokaryotic) pathway is deficient in the mutant. When exogenous [14C]18:1 was supplied, a eukaryotic (cytoplasmic) pathway involving the desaturation of 18:2 to 18:3 on phosphatidylcholine serves as the source of 18:3 for the sn-2 position of MGDG. This eucaryotic pathway predominates in the mutant. 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)

Srivastava, Hari S.; Ormrod, Douglas P.

doi: 10.1104/pp.81.3.737pmid: 16664894

Abstract The influence of nutrient nitrate level (0-20 millimolar) on the effects of NO2 (0-0.5 parts per million) on nodulation and in vivo acetylene reduction activity of the roots and on growth and nitrate and Kjeldahl N concentration in shoots was studied in bean (Phaseolus vulgaris L. cv Kinghorn Wax) plants. Exposing 8-day old seedlings for 6 hours each day, for 15 days, to 0.02 to 0.5 parts per million NO2 decreased total nodule weight at 0 and 1 millimolar nitrate, and nitrogenase (acetylene reduction) activity at all concentrations of nitrate. The pollutant had little effect on root fresh or dry weights. Shoot growth was inhibited by NO2. The NO2 exposure increased nitrate concentration in roots only at 20 millimolar nutrient nitrate. Exposure to NO2 markedly increased Kjeldahl N concentration in roots but generally decreased that in shoots. The experiments demonstrated that nutrient N level and NO2 concentration act jointly in affecting nodulation and N fixing capability, plant growth and composition, and root/shoot relationships of bean plants. 2 Recipient of a Visiting Research Associateship sponsored by the Canadian International Development Agency and the Natural Sciences and Engineering Research Council of Canada. 1 Supported by Natural Sciences and Engineering Research Council of Canada operating grant to D. P. Ormrod. 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)

Lazof, Dennis; Cheeseman, John M.

doi: 10.1104/pp.81.3.742pmid: 16664895

Abstract In this paper, a combination of tracer uptake, efflux, and pulse-chase techniques is applied to the problem of compartmentation of Na+ (24Na+) in the roots of intact, midvegetative Spergularia marina (L.) Griseb. plants. An approach is presented for conducting useful compartmental analysis when it is known that the assumptions required for straightforward interpretations of influx and efflux studies are invalid. Linear rates of 24Na+ accumulation in both roots and shoots were attained within at most a few minutes following the start of labeling. Shoot 24Na+ contents equaled root contents within about 20 minutes. Analysis of root accumulation rates, and compartmental and pulse-chase efflux studies indicated that the unidirectional flux rates involved were at least an order of magnitude greater than linear rates of root and shoot accumulation. These rapid fluxes involved only a small portion of the total root Na+ (about 1%). The results suggest the existence of a small symplastic compartment, distinct from the `bulk cytoplasm,' rapidly exchanging with the medium, and responsible for delivery of Na+ to the xylem. The physical identity of this compartment and its physiological significance are discussed with respect to precedents in the literature. 1 Supported by grant PCM 83-04417 from the National Science Foundation. 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)

Krishnan, Hari B.; Okita, Thomas W.

doi: 10.1104/pp.81.3.748pmid: 16664896

Abstract When the glutelin protein fraction of rice (Oryza sativa L.) seeds was fractionated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, three size classes of proteins, 51 kilodaltons (kD), 34 to 37 kD, and 21 to 22 kD, as well as a contaminating prolamine polypeptide of 14 kD were detected. Antibodies were raised against these proteins and employed in studies to determine whether a precursor-product relationship existed among the glutelin components. Antibodies of the 34 to 37 kD and 21 to 22 kD polypeptides strongly reacted with the 51 kD protein, and conversely, anti-51 kD protein cross reacted with both of the putative subunits. Immunoprecipitation of in vitro translated products resulted in the synthesis of only the precursor form, indicating that the α and β subunits are proteolytic products of the 51 kD precursor protein. The poly(A)+ RNA directed in vitro translated product was about 2000 daltons larger than both the authentic glutelin precursor and the in vitro translated product from polysome run-off synthesis. Western blot analysis of the 34 to 37 kD and 21 to 22 kD polypeptides partially digested with Staphylococcus aureus V8 protease revealed distinct patterns indicating that these proteins are structurally unrelated. As observed for the glutelins, the rice prolamines are also synthesized as a precursor of 16 kD, 2000 daltons larger than the mature polypeptide. Addition of dog pancreatic microsomal membranes to a wheat germ protein translation system resulted in the processing of the prolamine preprotein but not the preproglutelin to the mature form. 1 Supported in part by a grant from the Rockefeller Foundation RF 84066. Scientific Paper 7340, Project 0590, College of Agriculture Research Center, Washington State University, Pullman, WA 99164. 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)

Yamaya, Tomoyuki; Oaks, Ann; Rhodes, David; Matsumoto, Hideaki

doi: 10.1104/pp.81.3.754pmid: 16664897

Abstract Metabolically competent mitochondria were isolated from pea and corn shoots on Percoll discontinuous density gradients. Rates of synthesis of [15N]glutamate were measured by gas chromatography-mass spectrometry after the incubation of mitochondria with either 2 millimolar [15N] H4+ or [15N]glycine in the presence of 1 millimolar citrate as the respiratory substrate. When [15N]H4+ was provided, mitochondria isolated from light-grown pea shoots synthesized [15N]glutamate with a rate of 2.64 nanomoles per hour per milligram mitochondrial protein. Corn mitochondria produced [15N]glutamate at a rate approximately 11 times greater than the pea mitochondria. Dark treatment during growth for the last 24 hours caused a slight reduction in the rate of synthesis in both species. When [15N]glycine was used, pea mitochondria synthesized [15N]glutamate with a rate of 6.32 nanomoles per hour per milligram protein. Rapid disappearance of [15N]glycine and synthesis of [15N]serine was observed with a molar ratio of 2 glycine to 0.78 serine. The rate of glutamate synthesis was only 0.2% that of serine, due in part to the dilution of [15N]H4+ by the [14N]H4+ pool in the mitochondria. The majority of the [15N]H4+ released from glycine appears to have been released from or remains unmetabolized in the mitochondria. Corn mitochondria showed no apparent disappearance of [15N]glycine and little synthesis of [15N]serine, indicating that our preparation originated primarily from mesophyll cells. Under our conditions of glycine/serine conversion, [15N]glutatmate was synthesized at a rate of 7% of that of [15N]serine synthesis by corn mitochondria. 1 Supported by grant in Aid of Science Research for the Ministry of Education, Science and Culture of Japan (No. 58390012) and from the National Science and Engineering Council of Canada (No. A2818) and by a travel grant from the Japanese Ministry of Education (A. O.). 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)

Ross, Stephen; Dainty, Jack

doi: 10.1104/pp.81.3.758pmid: 16664898

Abstract Certain inhibitors have been found to affect the low frequency spectral component of the electrical noise power spectrum in Chara corallina. Application of the ATPase inhibitor N,N′-dicyclohexylcarbodiimide removed the low frequency spectral component, strengthening the case that the component is produced by active proton pumping. Cytocholasin B, which inhibits cyclosis in internodes of C. corallina, removed the low frequency spectral component in a time-dependent fashion which was correlated with the cessation of streaming. The protonophore carbonyl cyanide m-chlorophenylhydrazone did not produce consistent effects on the low frequency spectral component in these cells. 2 Present address: Musculoskeletal Research Group, Department of Surgery, University of Calgary, Rm 1714 Health Sciences Centre, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1. 1 Funded by a grant from the Natural Sciences and Engineering Research Council (NSERC). S. Ross was supported by a NSERC Postgraduate Scholarship and an Ontario Graduate Scholarship. 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)

Smith, Steven M.; Leaver, Christopher J.

doi: 10.1104/pp.81.3.762pmid: 16664899

Abstract A cDNA clone for the glyoxysomal enzyme malate synthase was isolated from a cDNA library made with polyadenylated RNA from the cotyledons of germinating Cucumis sativus L. This cloned DNA sequence was used as a probe to characterize changes in the amounts of malate synthase gene transcripts in cotyledons of cucumber seeds grown both in the light and in the dark. Malate synthase gene transcripts increase in amount to a peak at day 3 or day 4, and thereafter decline. In the light, this rate of decline is significantly greater than in the dark. Measurement of the changes in the amounts of malate synthase by assaying enzyme activity directly, and by immunological reaction with a specific antiserum indicate that the developmentally regulated synthesis of malate synthase in germinating cucumber is brought about primarily by changes in the amount of malate synthase gene transcripts, rather than through a control of translation. Similarly, the effect of light on the amount of malate synthase correlates precisely with its effect on the abundance of malate synthase gene transcripts. 1 Supported by the Agricultural and Food Research Council. 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)