Plant Physiology

Bray, E. A.

doi: 10.1104/pp.103.4.1035pmid: 12231998

Article PDF first page preview Close This content is only available as a PDF. Copyright © 1993 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)

Kempin, S. A.; Mandel, M. A.; Yanofsky, M. F.

doi: 10.1104/pp.103.4.1041pmid: 7507255

Abstract Mutations in the AGAMOUS (AG) gene of Arabidopsis thaliana result in the conversion of reproductive organs, stamens and carpels, into perianth organs, sepals and petals. We have isolated and characterized the putative AG gene from Nicotiana tabacum, NAG1, whose deduced protein product shares 73% identical amino acid residues with the Arabidopsis AG gene product. RNA tissue in situ hybridizations show that NAG1 RNA accumulates early in tobacco flower development in the region of the floral meristem that will later give rise to stamens and carpels. Ectopic expression of NAG1 in transgenic tobacco plants results in a conversion of sepals and petals into carpels and stamens, respectively, indicating that NAG1 is sufficient to convert perianth into reproductive floral organs. This content is only available as a PDF. Copyright © 1993 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)

Horvath, D. P.; McLarney, B. K.; Thomashow, M. F.

doi: 10.1104/pp.103.4.1047pmid: 8290624

Abstract Changes in gene expression occur during cold acclimation in a variety of plants including Arabidopsis thaliana L. (Heyn). Here we examine the cold-regulated expression of A. thaliana cor78. The results of gene-fusion experiments confirm the finding of Yamaguchi-Shinozaki and Shinozaki ([1993] Mol Gen Genet 236: 331–340) that the 5[prime] region of cor78 has cis-acting regulatory elements that can impart cold-regulated gene expression. Further, histochemical staining experiments indicated that this cold-regulatory element(s) was active at low temperature throughout much of the plant including leaves, stems, roots, flower petals, filaments, and sepals. Time-course experiments indicated that the activity of the cor78 promoter in cold-acclimated plants was down-regulated quickly in response to noninducing temperatures and that the half-life of the cor78 transcripts was only about 40 min at normal growth temperature. Fusion of the entire transcribed region of cor78 to the cauliflower mosaic virus 35S promoter resulted in a chimeric gene that was constitutively expressed and displayed little if any posttranscriptional regulation in response to low temperature. This content is only available as a PDF. Copyright © 1993 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)

Marrison, J. L.; Onyeocha, I.; Baker, A.; Leech, R. M.

doi: 10.1104/pp.103.4.1055pmid: 12231999

Abstract We report the visualization of peroxisomes in tobacco (Nicotiana tabacum) leaves using fluorescently labeled antibodies to glycolate oxidase. In transgenic tobacco leaves the expression of isocitrate lyase was also visualized. In dual probing experiments both enzymes were shown to be present together in all peroxisomes in transgenic tobacco leaves. This content is only available as a PDF. Copyright © 1993 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)

Gijzen, M.; van Huystee, R.; Buzzell, R. I.

doi: 10.1104/pp.103.4.1061pmid: 12232000

Abstract Peroxidase activity in the seed coats of soybean (Glycine max [L.] Merr.) is controlled by the Ep locus. We compared peroxidase activity in cell-free extracts from seed coat, root, and leaf tissues of three EpEp cultivars (Harosoy 63, Harovinton, and Coles) to three epep cultivars (Steele, Marathon, and Raiden). Extracts from the seed coats of EpEp cultivars were 100-fold higher in specific activity than those from epep cultivars, but there was no difference in specific activity in crude root or leaf extracts. Isoelectric focusing of root tissue extracts and staining for peroxidase activity showed that EpEp cultivars had a root peroxidase of identical isoelectric point to the seed coat peroxidase, whereas roots of the epep types were lacking that peroxidase, indicating that the Ep locus may also affect expression in the root. In seed coat extracts, peroxidase was the most abundant soluble protein in EpEp cultivars, whereas this enzyme was present only in trace amounts in epep genotypes, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Histochemical localization of peroxidase activity in seed coats of EpEp cultivars shows that the enzyme occurs predominately in the cytoplasm of hourglass cells of the subepidermis. No obvious difference in the gross or microscopic structure of the seed coat was observed to be associated with the Ep locus. These results suggest that soybean seed coat peroxidase may be involved in processes other than seed coat biosynthesis. This content is only available as a PDF. Copyright © 1993 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)

Gupta, A. S.; Webb, R. P.; Holaday, A. S.; Allen, R. D.

doi: 10.1104/pp.103.4.1067pmid: 12232001

Abstract Photosynthesis of leaf discs from transgenic tobacco plants (Nicotiana tabacum) that express a chimeric gene that encodes chloroplast-localized Cu/Zn superoxide dismutase (SOD+) was protected from oxidative stress caused by exposure to high light intensity and low temperature. Under the same conditions, leaf discs of plants that did not express the pea SOD isoform (SOD-) had substantially lower photosynthetic rates. Young plants of both genotypes were more sensitive to oxidative stress than mature plants, but SOD+ plants retained higher photosynthetic rates than SOD- plants at all developmental stages tested. Not surprisingly, SOD+ plants had approximately 3-fold higher SOD specific activity than SOD- plants. However, SOD+ plants also exhibited a 3- to 4-fold increase in ascorbate peroxidase (APX) specific activity and had a corresponding increase in levels of APX mRNA. Dehydroascorbate reductase and glutathione reductase specific activities were the same in both SOD+ and SOD- plants. These results indicate that transgenic tobacco plants that overexpress pea Cu/Zn SOD II can compensate for the increased levels of SOD with increased expression of the H2O2-scavenging enzyme APX. Therefore, the enhancement of the active oxygen-scavenging system that leads to increased oxidative stress protection in SOD+ plants could result not only from increased SOD levels but from the combined increases in SOD and APX activity. This content is only available as a PDF. Copyright © 1993 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)

Masle, J.; Hudson, G. S.; Badger, M. R.

doi: 10.1104/pp.103.4.1075pmid: 12232002

Abstract Growth of the R1 progeny of a tobacco plant (Nicotiana tabacum) transformed with an antisense gene to the small subunit of ribulose-1,5-carboxylase/oxygenase (Rubisco) was analyzed under 330 and 930 [mu]bar of CO2, at an irradiance of 1000 [mu]mol quanta m-2 s-1. Rubisco activity was reduced to 30 to 50% and 13 to 18% of that in the wild type when one and two copies of the antisense gene, respectively, were present in the genome, whereas null plants and wild-type plants had similar phenotypes. At 330 [mu]bar of CO2 all antisense plants were smaller than the wild type. There was no indication that Rubisco is present in excess in the wild type with respect to growth under high light. Raising ambient CO2 pressure to 930 [mu]bar caused plants with one copy of the DNA transferred from plasmid to plant genome to achieve the same size as the wild type at 330 [mu]bar, but plants with two copies remained smaller. Differences in final size were due mostly to early differences in relative rate of leaf area expansion (m2 m-2 d-1) or of biomass accumulation (g g-1 d-1): within less than 2 weeks after germination relative growth rates reached a steady-state value similar for all plants. Plants with greater carboxylation rates were characterized by a higher ratio of leaf carbon to leaf area, and at later stages, they were characterized also by a relatively greater allocation of structural and nonstructural carbon to roots versus leaves. However, these changes per se did not appear to be causing the long-term insensitivity of relative growth rates to variations in carboxylation rate. Nor was this insensitivity due to feedback inhibition of photosynthesis in leaves grown at high partial pressure of CO2 in the air (pa) or with high Rubisco activity, even when the amount of starch approached 40% of leaf dry weight. We propose that other intrinsic rate-limiting processes that are independent of carbohydrate supply were involved. Under plentiful nitrogen supply, reduction in the amount of nitrogen invested in Rubisco was more than compensated for by an increase in leaf nitrate. Nitrogen content of organic matter, excluding Rubisco, was unaffected by the antisense gene. In contrast, it was systematically lower at elevated pa than at normal pa. Combined with the positive effects of pa on growth, this resulted in the single-dose antisense plants growing as fast at 930 [mu]bar of CO2 as the wild-type plants at 330 [mu]bar of CO2 but at a lower organic nitrogen cost. This content is only available as a PDF. Copyright © 1993 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)

Bastide, B.; Sipes, D.; Hann, J.; Ting, I. P.

doi: 10.1104/pp.103.4.1089pmid: 12232003

Abstract Xerosicyos danguyi H.Humb. (Cucurbitaceae) is a Crassulacean acid metabolism (CAM) species native to Madagascar. Previously, it was shown that when grown under good water conditions, it is a typical CAM plant, but when water stressed, it shifts to a dampened form of CAM, termed CAM-idling, in which stomata are closed day and night but with a continued, low diurnal organic acid fluctuation. We have now studied the kinetics of some metabolic features of the shift from CAM to CAM-idling under severe water stress and the recovery upon rewatering. When water is withheld, there is a steady decrease in relative water content (RWC), reaching about 50%, at which point the water potential decreases precipitously from about -2 or -3 bars to -12 bars. Abscisic acid (ABA) increases sharply at about 75% RWC. Stomata close, which limits CO2 uptake, and there is a dampened diurnal organic acid fluctuation typical of CAM-idling. Throughout an extended stress period to 50% RWC, there is no change in chlorophyll, protein, and ribulose bisphosphate carboxylase activity compared with the well-watered plants. Despite the fact that the tissue was already in CAM, the stress is accompanied by an increase in phosphoenolpyruvate carboxylase (PEPc) mRNA, extractable PEPc activity, and PEPc protein (such that the specific activity remained approximately constant) and a decrease in the apparent Km(PEP). It is not known if the changes in Km(PEP) in response to drought are related to or are separate from the increases in PEPc protein and mRNA. The changes in Km(PEP) could be in response to the decreased endogenous levels of organic acids, but evidently are not an assay artifact. The increases in PEPc protein and mRNA appear to be related to the water-stress treatment and may result from the increased concentration of ABA or the decreased levels of endogenous organic acids. When rewatered, the metabolism quickly returns to the well-watered control typical of CAM. This content is only available as a PDF. Copyright © 1993 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)

Amsellem, Z.; Jansen, MAK.; Driesenaar, ARJ.; Gressel, J.

doi: 10.1104/pp.103.4.1097pmid: 12232004

Abstract Paraquat-resistant hairy fleabane (Conyza bonariensis L. Cronq.) has been extensively studied, with some contention. A single, dominant gene pleiotropically controls levels of oxidant-detoxifying enzymes and tolerance to many photooxidants, to photoinhibition, and possibly to other stresses. The weed forms a rosette on humid short days and flowers in dry long days and, thus, needs plasticity to photooxidant stresses. In a series of four experiments over 20 months, the resistant and susceptible biotypes were cultured in constant 10-h low-light short days at 25[deg]C. Resistance was measured as recovery from paraquat. The concentration required to achieve 50% inhibition of the resistant biotype was about 30 times that of the susceptible one just after germination, increased to >300 times that of the susceptibles at 10 weeks of growth, and then decreased to 20-fold, remaining constant except for a brief increase while bolting. Resistance increased when plants were induced to flower by long days. The levels of plastid superoxide dismutase and of glutathione reductase were generally highest in resistant plants compared to those of the susceptibles at the times of highest paraquat resistance, but they were imperceptibly different from the susceptible type at the times of lower paraquat resistance. Photoinhibition tolerance measured as quantum yield of oxygen evolution at ambient temperatures was highest when the relative amounts of enzymes were highest in the resistant biotype. Resistance to photoinhibition was not detected by chlorophyll a fluorescence. Enzyme levels, photoinhibition tolerance, and paraquat resistance all increased during flowering in both biotypes. Imperceptibly small increases in enzyme levels would be needed for 20-fold resistance, based on the moderate enzyme increases correlated with 300-fold resistance. Thus, it is feasible that either these enzymes play a role in the first line of defense against photooxidants, or another, yet unknown mechanism(s) facilitate(s) the lower level of resistance, or the enzymes and unknown mechanisms act together. This content is only available as a PDF. Copyright © 1993 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)

Bernstein, N.; Lauchli, A.; Silk, W. K.

doi: 10.1104/pp.103.4.1107pmid: 12232005

Abstract In many salt-sensitive species, elevated concentrations of Ca in the root growth media ameliorate part of the shoot growth reduction caused by NaCl stress. The physiological mechanisms by which Ca exerts protective effects on leaf growth are still not understood. Understanding growth inhibition caused by a stress necessitates locating the leaf expansion region and quantifying the profile of the growth reduction. This will enable comparisons and correlations with spatial gradients of probable physiologically inhibiting factors. In this work we applied the methods of growth kinematics to analyze the effects of elevated Ca concentrations on the spatial and temporal distributions of growth within the intercalary expanding region of salinized sorghum (Sorghum bicolor [L.] Moench, cv NK 265) leaves. NaCl (100 mM) caused a decrease in leaf elongation rate by shortening the leaf growing zone by 20%, as well as reducing the peak value of the longitudinal relative elemental growth rate (REG rate). Increasing the Ca concentrations from 1 to 10 mM restored the length of the growing zone of both emerged and unemerged salinized leaves and increased the peak value of the REG rate. The beneficial effects of supplemental Ca were, however, more pronounced in leaves after their appearance above the whorl of encircling older leaf sheaths. Elevated Ca then resulted in a peak value of REG rate higher than in the salinized leaves. The peak value of unemerged leaves was not increased, although it was maintained over a longer distance. The duration of elongation growth associated with a cell during its displacement from the leaf base was longer in salinized than control leaves, despite the fact that the elongation zone was shorter in salinity. Although partially restoring the length of the elongation region, supplemental Ca had no effect on the age of cessation of growth. Elongation of a tissue element, therefore, ceased when a cellular element reached a certain age and not a specific distance from the leaf base. This content is only available as a PDF. Copyright © 1993 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)