Plant Physiology

Kaplan, Aaron; Schwarz, Rakefet; Lieman-Hurwitz, Judy; Reinhold, Leonora

doi: 10.1104/pp.97.3.851pmid: 16668522

Abstract This paper reviews progress made in elucidating the inorganic carbon concentrating mechanism in cyanobacteria at the physiological and molecular levels. Emphasis is placed on the mechanism of inorganic carbon transport, physiological and genetical analysis of high-CO2-requiring mutants, the polypeptides induced during adaptation to low CO2, the functional significance of carboxysomes, and the role of carbonic anhydrase. We also make occasional reference to the green algal inorganic carbon-concentrating mechanism. 1 Research in our laboratory is supported by grants from the U.S.-Israel Binational Science Foundation, and from the National Council for Research and Development, Israel, and the GBF, Braunschweig, Germany. This content is only available as a PDF. © 1991 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)

Datta, Pradip K.; Figueroa, Maria O. D. C. R.; Lajolo, Franco M.

doi: 10.1104/pp.97.3.856pmid: 16668523

Abstract Two major lectins (lectin I and lectin II) were purified to homogeneity from the seeds of Araucaria brasiliensis (Gymnospermae). The purity of the lectins was confirmed by polyacrylamide gel electrophoresis, isoelectric focusing, and high performance liquid chromatography. They are glycoproteins in nature containing 6.3 and 2.9%, respectively, of neutral sugar and have absorption coefficients of 3.8 and 4.7, respectively, at 280 nanometers. The molecular weights of both lectins obtained by gel filtration on Sephacryl S-400 were equal: 200,000. After dissociation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, molecular weights were 20,000 and 34,000, respectively, for lectin I and lectin II, suggesting they are decameric and hexameric in nature. The amino acid composition of both lectins showed little difference, but both had high amounts of acidic amino acids and lacked methionine in their molecule. The carbohydrate binding specificity of lectins was directed towards mannose, glucose, and their oligomers. High inhibitory activity was also found with thyroglobulin. The erythroagglutinating activity of the lectins was enhanced in the presence of high-molecular-weight substances both at 37 and 4°C. Divalent cations do not appear to be essential for activity. They maintained their agglutinating activity over a broad but different range of pH: 5.5 to 7.5 and 6.5 to 7.5, respectively. Both lectins agglutinated erythrocytes of human ABO blood types equally well. 1 The research was developed and funded within the Depto. de Alimentos e Nutrição Experimental of São Paulo University while Dr. P. K. Datta was a postdoctoral fellow of the program CNPq-USP. This content is only available as a PDF. © 1991 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)

Foyer, Christine; Lelandais, Maud; Galap, Camille; Kunert, Karl Josef

doi: 10.1104/pp.97.3.863pmid: 16668524

Abstract Tobacco (Nicotiana tabacum var Samsun) was transformed using the bacterial gor gene coding for the enzyme glutathione reductase. Transgenic plants were selected by their kanamycin resistence and expression of the bacterial gor gene. After separation by isoelectric focusing techniques, leaf extracts from transgenic plants having both native and bacterial glutathione reductase activity gave, in addition to the six bands of the native enzyme, two further closely running isoenzymes. These additional bands originating from the expression of the bacterial gor gene were nonchloroplastic. Leaves from transgenic plants had two- to 10-fold higher glutathione reductase activity than non-transgenic controls. The amount of extractable glutathione reductase activity obtained in transgenic plants was dependent on leaf age and the conditions to which leaves were exposed. Both light and exposure to methylviologen increased leaf glutathione reductase activity. Elevated levels of cytosolic glutathione reductase activity in transgenic plants had no effect on the amount or reduction state of the reduced glutathione/oxidized glutathione pool under optimal conditions or oxidative conditions induced by methylviologen. The glutathione pool was unaltered despite the oxidation-dependent loss of CO2 assimilation and oxidation of enzymes involved in photosynthesis. However, the reduction state of the ascorbate pool was greater in transgenic plants relative to nontransgenic controls following illumination of methylviologen-treated leaf discs. Therefore, we conclude that in the natural state glutathione reductase is present in tobacco at levels above those required for maximal operation of the ascorbate-glutathione pathway. 1 Present address: AECI Limited, Research and Development Department, PO Modderfontein 1645, South Africa. This content is only available as a PDF. © 1991 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)

LaBrie, Samuel T.; Wilkinson, Jack Q.; Crawford, Nigel M.

doi: 10.1104/pp.97.3.873pmid: 16668525

Abstract The herbicide chlorate has been used extensively to isolate mutants that are defective in nitrate reduction. Chlorate is a substrate for the enzyme nitrate reductase (NR), which reduces chlorate to the toxic chlorite. Because NR is a substrate (NO3−)-inducible enzyme, we investigated the possibility that chlorate may also act as an inducer. Irrigation of ammonia-grown Arabidopsis plants with chlorate leads to an increase in NR mRNA in the leaves. No such increase was observed for nitrite reductase mRNA following chlorate treatment; thus, the effect seems to be specific to NR. The increase in NR mRNA did not depend on the presence of wild-type levels of NR activity or molybdenum-cofactor, as a molybdenum-cofactor mutant with low levels of NR activity displayed the same increase in NR mRNA following chlorate treatment. Even though NR mRNA levels were found to increase after chlorate treatment, no increase in NR protein was detected and the level of NR activity dropped. The lack of increase in NR protein was not due to inactivation of the cells' translational machinery, as pulse labeling experiments demonstrated that total protein synthesis was unaffected by the chlorate treatment during the time course of the experiment. Chlorate-treated plants still retain the capacity to make functional NR because NR activity could be restored by irrigating the chlorate-treated plants with nitrate. The low levels of NR protein and activity may be due to inactivation of NR by chlorite, leading to rapid degradation of the enzyme. Thus, chlorate treatment stimulates NR gene expression in Arabidopsis that is manifested only at the mRNA level and not at the protein or activity level. 1 This work was supported by grants to N.M.C. from the Powell Foundation and the National Institutes of Health (1R29GM40672-01) and to S.T.L. from the San Diego Fellowship program. This content is only available as a PDF. © 1991 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)

Kim, Jong Jin; Ben-Yehoshua, Shimshon; Shapiro, Boris; Henis, Yigal; Carmeli, Shmuel

doi: 10.1104/pp.97.3.880pmid: 16668526

Abstract Phytoalexin scoparone (6,7-dimethoxycoumarin) generally was not detected in noninoculated lemon fruit (Citrus limon [L.] Burm., cv Eureka) but accumulated in fruit after inoculation with Penicillium digitatum Sacc. A much greater increase in the amount of scoparone was found in fruit exhibiting an incompatible response to Penicillium after heat treatment at 36°C for 3 days. Heat treatment prevented development of decay in the inoculated fruit. The concentration of the compound after inoculation continued to increase during and after the heat treatment period, reaching 178 micrograms per gram fresh weight of the flavedo 6 days after the heat treatment. Changes in scoparone concentration in fruit were closely correlated with the changes in the antifungal activity of the fruit extract. A low concentration of the phytoalexin was detected in fruit injured mechanically. Scoparone also accumulated in the fruit following ultraviolet illumination; the concentration of the compound was dose-dependent. Median effective dose values of the inhibition of germ tube elongation and spore germination of P. digitatum were 29 and 46 micrograms per milliliter, respectively. Our findings suggest that the rapid increase in scoparone concentration plays an important role in the increased resistance of heat-treated lemon fruit to infection by P. digitatum. 1 This work was supported in part by a grant from the United States-Israel Binational Agricultural Research and Development Fund and by a scholarship from the Center for International Cooperation in Agricultural Research of Israel, given to the senior author. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 3178-E, 1991 series. This content is only available as a PDF. © 1991 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)

Morales, Fermín; Abadía, Anunciación; Abadía, Javier

doi: 10.1104/pp.97.3.886pmid: 16668527

Abstract The response of sugar beet (Beta vulgaris L.) leaves to iron deficiency can be described as consisting of two phases. In the first phase, leaves may lose a large part of their chlorophyll while maintaining a roughly constant efficiency of photosystem II photochemistry; ratios of variable to maximum fluorescence decreased by only 6%, and photon yields of oxygen evolution decreased by 30% when chlorophyll decreased by 70%. In the second phase, when chlorophyll decreased below a threshold level, iron deficiency caused major decreases in the efficiency of photosystem II photochemistry and in the photon yield of oxygen evolution. These decreases in photosystem II photochemical efficiency were found both in plants dark-adapted for 30 minutes and in plants dark-adapted overnight, indicating that photochemical efficiency cannot be repaired in that time scale. Decreases in photosystem II photochemical efficiency and in the photon yield of oxygen evolution were similar when measurements were made (a) with light absorbed by carotenoids and chlorophylls and (b) with light absorbed only by chlorophylls. Leaves of iron-deficient plants exhibited a room temperature fluorescence induction curve with a characteristic intermediate peak I that increases with deficiency symptoms. 1 Supported by grants from Dirección General de Investigación Científica y Técnica PB88-0084 and Consejo Asesor de Investigación-Diputación General de Aragón CA 8/88. F.M. was supported by a fellowship from the Consejo Asesor de Investigación-Diputación General de Aragón. J.A. was a collaborator via fellowship under OECD Project on Food Production and Preservation. 2 This paper is dedicated to the memory of Professor Cruz Rodríguez Muñoz, a pioneer in the field of plant physiology in Spain. This content is only available as a PDF. © 1991 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)

Holbrook, Gabriel P.; Galasinski, Scott C.; Salvucci, Michael E.

doi: 10.1104/pp.97.3.894pmid: 16668528

Abstract The regulation of 2-carboxyarabinitol 1-phosphatase (CA 1-Pase) by phosphorylated effectors was studied with enzyme purified from tobacco (Nicotiana tabacum) leaves. CA 1-Pase activity was most stimulated by fructose 1,6-bisphosphate, exhibiting an A 0.5 value of 1.9 millimolar and a 10-fold enhancement of catalysis. With ribulose-1,5-bisphosphate, the A 0.5 was 0.6 millimolar, and maximal stimulation of activity was 5.3-fold. Among the monophosphates, 3-phosphoglycerate and phosphoglycolate were more potent positive effectors than glyceraldehyde 3-phosphate, glucose 1-phosphate, glucose 6-phosphate, and dihydroxyacetone phosphate. Stimulation of CA 1-Pase by ribulose-1,5-bisphosphate and fructose 1,6-bisphosphate increased V max but did not appreciably alter K m (2-carboxyarabinitol 1-phosphate) values. Inorganic phosphate appeared to inhibit CA 1-Pase noncompetitively with respect to 2-carboxyarabinitol 1-phosphate, exhibiting a K i of 0.3 millimolar. The results suggest that these positive and negative effectors bind to a regulatory site on CA 1-Pase and may have a physiologial role in the light regulation of this enzyme. Related experiments with CA 1-Pase inactivated by dialysis in the absence of dithiothreitol show that partial reactivation can be achieved in the presence of a range of reducing reagents, including dithiothreitol, cysteine, and reduced glutathione. This could imply an ancillary involvement of sulfhydryl reduction during light activation of CA 1-Pase in vivo. The enzyme was thermally stable up to 35°C, in contrast to ribulose-1,5-bisphosphate carboxylase/oxygenase activase which lost activity above 30°C. The activation energy for CA 1-Pase was calculated to be 56.14 kilojoules per mole. 1 Supported in part by BRSG SO7 RRO7176 awarded to G.P.H. by the Biomedical Research Grant Program, Division of Research Resources, National Institutes of Health. We also acknowledge support from the Graduate School and the Plant Molecular Biology Center at Northern Illinois University. This content is only available as a PDF. © 1991 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)

Plant, Áine L.; Cohen, Amybeth; Moses, Meena S.; Bray, Elizabeth A.

doi: 10.1104/pp.97.3.900pmid: 16668529

Abstract The nucleotide sequence of le16, a tomato (Lycopersicon esculentum Mill.) gene induced by drought stress and regulated by abscisic acid specifically in aerial vegetative tissue, is presented. The single open reading frame contained within the gene has the capacity to encode a polypeptide of 12.7 kilodaltons and is interrupted by a small intron. The predicted polypeptide is rich in leucine, glycine, and alanine and has an isoelectric point of 8.7. The amino terminus is hydrophobic and characteristic of signal sequences that target polypeptides for export from the cytoplasm. There is homology (47.2% identity) between the amino terminus of the LE 16 polypeptide and the corresponding amino terminal domain of the maize phospholipid transfer protein. le16 was expressed in drought-stressed leaf, petiole, and stem tissue and to a much lower extent in the pericarp of mature green tomato fruit and developing seeds. No expression was detected in the pericarp of red fruit or in drought-stressed roots. Expression of le16 was also induced in leaf tissue by a variety of other abiotic stresses including polyethylene glycol-mediated water deficit, salinity, cold stress, and heat stress. None of these stresses or direct applications of abscisic acid induced the expression of le16 in the roots of the same plants. The unique expression characteristics of this gene indicates that novel regulatory mechanisms, in addition to endogenous abscisic acid, are involved in controlling gene expression. 1 This work was supported by U.S. Department of Agriculture Grant 88-37264-3925, the Department of Botany and Plant Sciences, and a Career Development Award to E.A.B. This content is only available as a PDF. © 1991 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)

Shackel, Kenneth A.; Polito, Vito S.; Ahmadi, Hamid

doi: 10.1104/pp.97.3.907pmid: 16668530

Abstract When leaf epidermal cells are puncture wounded with a glass microcapillary tip, a small droplet of fluid is discharged and then evaporates, leaving a solid residue on the cell surface. For puncture wounds of about 3.5 micrometers in diameter, this process is complete within 2 to 3 seconds. A second puncture wound also exhibits a similar discharge, indicating the persistence of some turgor pressure within the cell, despite damage to the cell wall. Direct measurement of turgor on the large epidermal cells of Tradescantia virginiana L. demonstrated that turgor was substantially maintained (91-96%) after puncture wounding. Anatomical and histochemical evidence suggests that the damaged portion of the cell wall was sealed with an amorphous plug of material comprised of pectinaceous polysaccharides. Rapid sealing of puncture wounds and the maintenance of turgor in epidermal cells may be an important functional component of plant adaptation to physical damage such as that caused by insect feeding. This content is only available as a PDF. © 1991 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)

Houtz, Robert L.; Royer, Malcolm; Salvucci, Michael E.

doi: 10.1104/pp.97.3.913pmid: 16668531

Abstract The large subunit (LS) of tobacco (Nicotiana rustica) ribulose-1,5-bisphosphate carboxylase/oxygenase (ribulose-P2 carboxylase) contains a trimethyllysyl residue at position 14, whereas this position is unmodified in spinach ribulose-P2 carboxylase. A protein fraction was isolated from tobacco chloroplasts by rate-zonal centrifugation and anion-exchange fast protein liquid chromatography that catalyzed transfer of methyl groups from S-adenosyl-[methyl-3H]-l-methionine to spinach ribulose-P2 carboxylase. 3H-Methyl groups incorporated into spinach ribulose-P2 carboxylase were alkaline stable but could be removed by limited tryptic proteolysis. Reverse-phase high-performance liquid chromatography of the tryptic peptides released after proteolysis showed that the penultimate N-terminal peptide from the LS of spinach ribulose-P2 carboxylase contained the site of methylation, which was identified as lysine-14. Thus, the methyltransferase activity can be attributed to S-adenosylmethionine:ribulose-P2 carboxylase LS (lysine) `N-methyltransferase, a previously undescribed chloroplast enzyme. The partially purified enzyme was specific for ribulose-P2 carboxylase and exhibited apparent K m values of 10 micromolar for S-adenosyl-l-methionine and 18 micromolar for ribulose-P2 carboxylase, a V max of 700 picomoles CH3 groups transferred per minute per milligram protein, and a broad pH optimum from 8.5 to 10.0. S-Adenosylmethionine:ribulose-P2 carboxylase LS (lysine)εN-methyltransferase was capable of incorporating 24 3H-methyl groups per spinach ribulose-P2 carboxylase holoenzyme, forming 1 mole of trimethyllysine per mole of ribulose-P2 carboxylase LS, but was inactive on ribulose-P2 carboxylases that contain a trimethyllysyl residue at position 14 in the LS. The enzyme did not distinguish between activated (Mg2+ and CO2) and unactivated forms of ribulose-P2 carboxylase as substrates. However, complexes of activated ribulose-P2 carboxylase with the reaction-intermediate analogue 2′-carboxy-d-arabinitol-1,5-bisphosphate, or unactivated spinach ribulose-P2 carboxylase with ribulose-1,5-bisphosphate, were poor substrates for tobacco LS εN-methyltransferase. 1 This work was supported by U.S. Department of Agriculture/Competitive Research Grants Office Grant 89-37262-4482 and Hatch Project KY 00586 to R.L.H. The investigation reported in this paper (No. 90-10-221) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director. This content is only available as a PDF. © 1991 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)