Plant Physiology

Ishikawa, H.; Evans, M. L.

doi: 10.1104/pp.109.3.725pmid: 11539165

Article PDF first page preview Close This content is only available as a PDF. Copyright © 1995 by 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)

Cote, G. G.

doi: 10.1104/pp.109.3.729pmid: 12228627

Article PDF first page preview Close This content is only available as a PDF. Copyright © 1995 by 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)

Niu, X.; Bressan, R. A.; Hasegawa, P. M.; Pardo, J. M.

doi: 10.1104/pp.109.3.735pmid: 12228628

Article PDF first page preview Close This content is only available as a PDF. Copyright © 1995 by 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, Q.; Monroe, J.; Sjolund, R. D.

doi: 10.1104/pp.109.3.743pmid: 8552713

Abstract A monoclonal antibody, RS 5, was raised by injecting sieve elements isolated from tissue cultures of Streptanthus tortuosus (Brassicaceae) into BALB/c mice and screening resultant hybridoma supernatants for the labeling of phloem using immunofluorescence microscopy. The RS 5 monoclonal antibody identifies a 57-kD protein on immunoblots, which is present in phloem-forming tissue cultures of S. tortuosus but is absent in cultures that lack phloem. Purified 57-kD protein of S. tortuosus is demonstrated to be a phloem-specific [beta]-amylase. Partial peptide sequences of the 57-kD protein of S. tortuosus are shown to be 96% identical with the corresponding portions of a deduced sequence reported for a major form of [beta]-amylase in Arabidopsis thaliana. The RS 5 antibody cross-reacts with the major form of A. thaliana [beta]-amylase on immunoblots, and the antibody also binds to the sieve elements of A. thaliana using immunofluorescence microscopy. The results suggest that the major form of A. thaliana [beta]-amylase is a phloem-specific enzyme. This content is only available as a PDF. Copyright © 1995 by 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)

Leubner-Metzger, G.; Frundt, C.; Vogeli-Lange, R.; Meins Jr, F.

doi: 10.1104/pp.109.3.751pmid: 12228629

Abstract Rupture of the seed coat and rupture of the endosperm are separate events in the germination of Nicotiana tabacum L. cv Havana 425 seeds. Treatment with 10–5 M abscisic acid (ABA) did not appreciably affect seed-coat rupture but greatly delayed subsequent endosperm rupture by more than 100 h and resulted in the formation of a novel structure consisting of the enlarging radicle with a sheath of greatly elongated endosperm tissue. Therefore, ABA appears to act primarily by delaying endosperm rupture and radicle emergence. Measurements of [beta]-1,3-glucanase activity, antigen content, and mRNA accumulation together with reporter gene experiments showed that induction of class I [beta]-1,3-glucanase genes begins just prior to the onset of endosperm rupture but after the completion of seed-coat rupture. This induction was localized exclusively in the micropylar region of the endosperm, where the radicle will penetrate. ABA treatment markedly inhibited the rate of [beta]-1,3-glucanase accumulation but did not delay the onset of induction. Independent of the ABA concentration used, onset of endosperm rupture was correlated with the same [beta]-1,3-glucanase content/seed. These results suggest that ABA-sensitive class I [beta]-1,3-glucanases promote radicle penetration of the endosperm, which is a key limiting step in tobacco seed germination. This content is only available as a PDF. Copyright © 1995 by 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)

Schaller, H.; Grausem, B.; Benveniste, P.; Chye, M. L.; Tan, C. T.; Song, Y. H.; Chua, N. H.

doi: 10.1104/pp.109.3.761pmid: 12228630

Abstract A genomic fragment encoding one (HMGR1) of the three 3-hydroxy-3-methylglutaryl coenzyme A reductases (HMGRs) from Hevea brasiliensis (H.B.K.) Mull. Arg. (M.-L. Chye, C.-T. Tan, N.-H. Chua [1992] Plant Mol Biol 19: 473–484) was introduced into Nicotiana tabacum L. cv xanthi via Agrobacterium transformation to study the influence of the hmg1 gene product on plant isoprenoid biosynthesis. Transgenic plants were morphologically indistinguishable from control wild-type plants and displayed the same developmental pattern. Transgenic lines showed an increase in the level of total sterols up to 6-fold, probably because of an increased expression level of hmg1 mRNA and a corresponding increased enzymatic activity for HMGR, when compared with the level of total sterols from control lines not expressing the hmg1 transgene. In addition to the pathway end products, campesterol, sitosterol, and stigmasterol, some biosynthetic intermediates such as cycloartenol also accumulated in transgenic tissues. Most of the overproduced sterols were detected as steryl-esters and were likely to be stored in cytoplasmic lipid bodies. These data strongly support the conclusion that plant HMGR is a key limiting enzyme in phytosterol biosynthesis. This content is only available as a PDF. Copyright © 1995 by 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)

Borrell, A.; Culianez-Macia, F. A.; Altabella, T.; Besford, R. T.; Flores, D.; Tiburcio, A. F.

doi: 10.1104/pp.109.3.771pmid: 12228631

Abstract Plants, unlike animals, can use either ornithine decarboxylase or arginine decarboxylase (ADC) to produce the polyamine precursor putrescine. Lack of knowledge of the exact cellular and subcellular location of these enzymes has been one of the main obstacles to our understanding of the biological role of polyamines in plants. We have generated polyclonal antibodies to oat (Avena sativa L.) ADC to study the spatial distribution and subcellular localization of ADC protein in different oat tissues. By immunoblotting and immunocytochemistry, we show that ADC is organ specific. By cell fractionation and immunoblotting, we show that ADC is localized in chloroplasts associated with the thylakoid membrane. The results also show that increased levels of ADC protein are correlated with high levels of ADC activity and putrescine in osmotically stressed oat leaves. A model of compartmentalization for the arginine pathway and putrescine biosynthesis in active photosynthetic tissues has been proposed. In the context of endosymbiote-driven metabolic evolution in plants, the location of ADC in the chloroplast compartment may have major evolutionary significance, since it explains (a) why plants can use two alternative pathways for putrescine biosynthesis and (b) why animals do not possess ADC This content is only available as a PDF. Copyright © 1995 by 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)

Zheng, Z.; Sumi, K.; Tanaka, K.; Murai, N.

doi: 10.1104/pp.109.3.777pmid: 12228632

Abstract The seed storage protein [beta]-phaseolin of the common bean (Phaseolus vulgaris L.) was expressed in the endosperm of transgenic rice (Oryza sativa L.) plants. The 5.1- or 1.8-kb promoter fragment of the rice seed storage protein glutelin Gt1 gene was fused transcriptionally to either the genomic or cDNA coding sequence of the [beta]-phaseolin gene. The highest quantity of phaseolin estimated by enzyme-linked immunosorbent assay was 4.0% of the total endosperm protein in the transgenic rice seeds. The phaseolin trait was segregated as a single dominant trait with a positive gene dosage effect and was stably inherited through three successive generations. Both phaseolin genomic and cDNA coding sequences were used to synthesize four isoforms of mature phaseolin protein with apparent molecular masses of 51, 48, 47, and 45 kD. Enzyme deglycosylation experiments indicated that the 51-kD form contains high-mannose N-glycans; the 48- and 47-kD forms have further modified N-glycans; and the 45-kD form is a nonglycosylated protein. Immunolabeling studies using light and electron microscopy demonstrated that phaseolin accumulates primarily in the vacuolar type-II protein bodies located at the periphery of the endosperm near the aleurone layer. We discuss the implications of these results on nutritional improvement of rice grains. This content is only available as a PDF. Copyright © 1995 by 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)

Maxwell, D. P.; Laudenbach, D. E.; Huner, NPA.

doi: 10.1104/pp.109.3.787pmid: 12228633

Abstract We demonstrate that photosynthetic adjustment at the level of the light-harvesting complex associated with photosystem II (LCHII) in Dunaliella salina is a response to changes in the redox state of intersystem electron transport as estimated by photosystem II (PSII) excitation pressure. To elucidate the molecular basis of this phenomenon, LHCII apoprotein accumulation and cab mRNA abundance were examined. Growth regimes that induced low, but equivalent, excitation pressures (either 13[deg]C/20 [mu]mol m-2 s-1 or 30[deg]C/150 ([mu]mol m-2 s-1) resulted in increased LHCII apoprotein and cab mRNA accumulation relative to algal cultures grown under high excitation pressures (either 13[deg]C/150 [mu]mol m-2 s-1 or 30[deg]C/2500 [mu]mol m-2 s-1). Thermodynamic relaxation of high excitation pressures, accomplished by shifting cultures from a 13 to a 30[deg]C growth regime at constant irradiance for 12 h, resulted in a 6- and 8-fold increase in LHCII apoprotein and cab mRNA abundance, respectively. Similarly, photodynamic relaxation of high excitation pressure, accomplished by a shift from a light to a dark growth regime at constant temperature, resulted in a 2.4- to 4-fold increase in LHCII apoprotein and cab mRNA levels, respectively. We conclude that photosynthetic adjustment to temperature mimics adjustment to high irradiance through a common redox sensing/signaling mechanism. Both temperature and light modulate the redox state of the first, stable quinone electron acceptor of PSII, which reflects the redox poise of intersystem electron transport. Changes in redox poise signal the nucleus to regulate cab mRNA abundance, which, in turn, determines the accumulation of light-harvesting apoprotein. This redox mechanism may represent a general acclimation mechanism for photosynthetic adjustment to environmental stimuli. This content is only available as a PDF. Copyright © 1995 by 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)

Waldo, G. S.; Wright, E.; Whang, Z. H.; Briat, J. F.; Theil, E. C.; Sayers, D. E.

doi: 10.1104/pp.109.3.797pmid: 8552714

Abstract Ferritin in plants is a nuclear-encoded, multisubunit protein found in plastids; an N-terminal transit peptide targets the protein to the plastid, but the site for formation of the ferritin Fe mineral is unknown. In biology, ferritin is required to concentrate Fe to levels needed by cells (approximately 10–7 M), far above the solubility of the free ion (10–18 M); the protein directs the reversible phase transition of the hydrated metal ion in solution to hydrated Fe-oxo mineral. Low phosphate characterizes the solid-phase Fe mineral in the center of ferritin of the cytosolic animal ferritin, but high phosphate is the hallmark of Fe mineral in prokaryotic ferritin and plant (pea [Pisum sativum L.] seed) ferritin. Earlier studies using x-ray absorption spectroscopy showed that high concentrations of phosphate present during ferritin mineralization in vitro altered the local structure of Fe in the ferritin mineral so that it mimicked the prokaryotic type, whether the protein was from animals or bacteria. The use of x-ray absorption spectroscopy to analyze the Fe environment in pea-seed ferritin now shows that the natural ferritin mineral in plants has an Fe-P interaction at 3.26A, similar to that of bacterial ferritin; phosphate also prevented formation of the longer Fe-Fe interactions at 3.5A found in animal ferritins or in pea-seed ferritin reconstituted without phosphate. Such results indicate that ferritin mineralization occurs in the plastid, where the phosphate content is higher; a corollary is the existence of a plastid Fe uptake system to allow the concentration of Fe in the ferritin mineral. This content is only available as a PDF. Copyright © 1995 by 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)