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12 pages, 2720 KiB

Open AccessArticle

Low-Oxygen Responses of Cut Carnation Flowers Associated with Modified Atmosphere Packaging

by Misaki Nakayama, Nao Harada, Ai Murai, Sayaka Ueyama and Taro Harada

Plants 2023, 12(14), 2738; https://doi.org/10.3390/plants12142738 - 23 Jul 2023

Cited by 1 | Viewed by 2143

Gaseous factors affect post-harvest physiological processes in horticultural crops, including ornamental flowers. However, the molecular responses of cut flowers to the low-oxygen conditions associated with modified atmosphere packaging (MAP) have not yet been elucidated. Here, we show that storage of cut carnation flowers in a sealed polypropylene bag decreased the oxygen concentration in the bag to 3–5% and slowed flower opening. The vase life of carnation flowers after storage for seven days under MAP conditions was comparable to that without storage and was improved by the application of a commercial-quality preservative. The adenylate energy charge (AEC) was maintained at high levels in petals from florets stored under MAP conditions. This was accompanied by the upregulation of four hypoxia-related genes, among which the HYPOXIA-RESPONSIVE ETHYLENE RESPONSE FACTOR and PHYTOGLOBIN genes (DcERF19 and DcPGB1) were newly identified. These results suggest that hypoxia-responsive genes contribute to the maintenance of the energy status in carnation flowers stored under MAP conditions, making this gas-controlling technique potentially effective for maintaining cut flower quality without cooling. Full article

(This article belongs to the Special Issue Molecular Mechanism of Petal Senescence and New Technology for the Extension of Flower Life)

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12 pages, 3364 KiB

Open AccessArticle

Conformational Dynamics of Phytoglobin BvPgb1.2 from Beta vulgaris ssp. vulgaris

by Simon Christensen, Olof Stenström, Mikael Akke and Leif Bülow

Int. J. Mol. Sci. 2023, 24(4), 3973; https://doi.org/10.3390/ijms24043973 - 16 Feb 2023

Cited by 1 | Viewed by 1958

Abstract

Plant hemoglobins, often referred to as phytoglobins, play important roles in abiotic stress tolerance. Several essential small physiological metabolites can be bound to these heme proteins. In addition, phytoglobins can catalyze a range of different oxidative reactions in vivo. These proteins are often oligomeric, but the degree and relevance of subunit interactions are largely unknown. In this study, we delineate which residues are involved in dimer formation of a sugar beet phytoglobin type 1.2 (BvPgb1.2) using NMR relaxation experiments. E. coli cells harboring a phytoglobin expression vector were cultivated in isotope-labeled (²H, ¹³C and ¹⁵N) M9 medium. The triple-labeled protein was purified to homogeneity using two chromatographic steps. Two forms of BvPgb1.2 were examined, the oxy-form and the more stable cyanide-form. Using three-dimensional triple-resonance NMR experiments, sequence-specific assignments for CN-bound BvPgb1.2 were achieved for 137 backbone amide cross-peaks in the ¹H-¹⁵N TROSY spectrum, which amounts to 83% of the total number of 165 expected cross-peaks. A large proportion of the non-assigned residues are located in α-helixes G and H, which are proposed to be involved in protein dimerization. Such knowledge around dimer formation will be instrumental for developing a better understanding of phytoglobins’ roles in planta. Full article

(This article belongs to the Section Molecular Biophysics)

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15 pages, 1487 KiB

Open AccessArticle

Nitric Oxide Metabolic Pathway in Drought-Stressed Nodules of Faba Bean (Vicia faba L.)

by Chaima Chammakhi, Alexandre Boscari, Marie Pacoud, Grégoire Aubert, Haythem Mhadhbi and Renaud Brouquisse

Int. J. Mol. Sci. 2022, 23(21), 13057; https://doi.org/10.3390/ijms232113057 - 27 Oct 2022

Cited by 10 | Viewed by 2762

Abstract

Drought is an environmental stress that strongly impacts plants. It affects all stages of growth and induces profound disturbances that influence all cellular functions. Legumes can establish a symbiosis with Rhizobium-type bacteria, whose function is to fix atmospheric nitrogen in organs called nodules and to meet plant nitrogen needs. Symbiotic nitrogen fixation (SNF) is particularly sensitive to drought. We raised the hypothesis that, in drought-stressed nodules, SNF inhibition is partly correlated to hypoxia resulting from nodule structure compaction and an increased O₂ diffusion barrier, and that the nodule energy regeneration involves phytoglobin–nitric oxide (Pgb–NO) respiration. To test this hypothesis, we subjected faba bean (Vicia faba L.) plants nodulated with a Rhizobium laguerreae strain to either drought or osmotic stress. We monitored the N₂-fixation activity, the energy state (ATP/ADP ratio), the expression of hypoxia marker genes (alcohol dehydrogenase and alanine aminotransferase), and the functioning of the Pgb–NO respiration in the nodules. The collected data confirmed our hypothesis and showed that (1) drought-stressed nodules were subject to more intense hypoxia than control nodules and (2) NO production increased and contributed via Pgb–NO respiration to the maintenance of the energy state of drought-stressed nodules. Full article

(This article belongs to the Special Issue Nitric Oxide Signalling and Metabolism in Plants)

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15 pages, 1722 KiB

Open AccessArticle

Oxidative Implications of Substituting a Conserved Cysteine Residue in Sugar Beet Phytoglobin BvPgb 1.2

by Simon Christensen, Leonard Groth, Nélida Leiva-Eriksson, Maria Nyblom and Leif Bülow

Antioxidants 2022, 11(8), 1615; https://doi.org/10.3390/antiox11081615 - 20 Aug 2022

Cited by 5 | Viewed by 2226

Abstract

Phytoglobins (Pgbs) are plant-originating heme proteins of the globin superfamily with varying degrees of hexacoordination. Pgbs have a conserved cysteine residue, the role of which is poorly understood. In this paper, we investigated the functional and structural role of cysteine in BvPgb1.2, a Class 1 Pgb from sugar beet (Beta vulgaris), by constructing an alanine-substituted mutant (Cys86Ala). The substitution had little impact on structure, dimerization, and heme loss as determined by X-ray crystallography, size-exclusion chromatography, and an apomyoglobin-based heme-loss assay, respectively. The substitution significantly affected other important biochemical properties. The autoxidation rate increased 16.7- and 14.4-fold for the mutant versus the native protein at 25 °C and 37 °C, respectively. Thermal stability similarly increased for the mutant by ~2.5 °C as measured by nano-differential scanning fluorimetry. Monitoring peroxidase activity over 7 days showed a 60% activity decrease in the native protein, from 33.7 to 20.2 U/mg protein. When comparing the two proteins, the mutant displayed a remarkable enzymatic stability as activity remained relatively constant throughout, albeit at a lower level, ~12 U/mg protein. This suggests that cysteine plays an important role in BvPgb1.2 function and stability, despite having seemingly little effect on its tertiary and quaternary structure. Full article

(This article belongs to the Special Issue Globin Associated Oxidative Stress)

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17 pages, 2481 KiB

Open AccessArticle

Phytoglobin Expression Alters the Na⁺/K⁺ Balance and Antioxidant Responses in Soybean Plants Exposed to Na₂SO₄

by Mohamed S. Youssef, Mohammed M. Mira, Sylvie Renault, Robert D. Hill and Claudio Stasolla

Int. J. Mol. Sci. 2022, 23(8), 4072; https://doi.org/10.3390/ijms23084072 - 7 Apr 2022

Cited by 12 | Viewed by 3065

Abstract

Soybean (Glycine max) is an economically important crop which is very susceptible to salt stress. Tolerance to Na₂SO₄ stress was evaluated in soybean plants overexpressing or suppressing the phytoglobin GmPgb1. Salt stress depressed several gas exchange parameters, including the photosynthetic rate, caused leaf damage, and reduced the water content and dry weights. Lower expression of respiratory burst oxidase homologs (RBOHB and D), as well as enhanced antioxidant activity, resulting from GmPgb1 overexpression, limited ROS-induced damage in salt-stressed leaf tissue. The leaves also exhibited higher activities of the H₂O₂-quenching enzymes, catalase (CAT) and ascorbate peroxidase (APX), as well as enhanced levels of ascorbic acid. Relative to WT and GmPgb1-suppressing plants, overexpression of GmPgb1 attenuated the accumulation of foliar Na⁺ and exhibited a lower Na⁺/K⁺ ratio. These changes were attributed to the induction of the Na⁺ efflux transporter SALT OVERLY SENSITIVE 1 (SOS1) limiting Na⁺ intake and transport and the inward rectifying K⁺ channel POTASSIUM TRANSPORTER 1 (AKT1) required for the maintenance of the Na⁺/K⁺ balance. Full article

(This article belongs to the Special Issue Nitric Oxide Signalling and Metabolism in Plants)

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16 pages, 567 KiB

Open AccessReview

Transduction of Signals during Somatic Embryogenesis

by Mohamed Elhiti and Claudio Stasolla

Plants 2022, 11(2), 178; https://doi.org/10.3390/plants11020178 - 11 Jan 2022

Cited by 51 | Viewed by 5108

Abstract

Somatic embryogenesis (SE) is an in vitro biological process in which bipolar structures (somatic embryos) can be induced to form from somatic cells and regenerate into whole plants. Acquisition of the embryogenic potential in culture is initiated when some competent cells within the explants respond to inductive signals (mostly plant growth regulators, PRGs), and de-differentiate into embryogenic cells. Such cells, “canalized” into the embryogenic developmental pathway, are able to generate embryos comparable in structure and physiology to their in vivo counterparts. Genomic and transcriptomic studies have identified several pathways governing the initial stages of the embryogenic process. In this review, the authors emphasize the importance of the developmental signals required for the progression of embryo development, starting with the de-differentiation of somatic cells and culminating with tissue patterning during the formation of the embryo body. The action and interaction of PGRs are highlighted, along with the participation of master regulators, mostly transcription factors (TFs), and proteins involved in stress responses and the signal transduction required for the initiation of the embryogenic process. Full article

(This article belongs to the Special Issue Mechanism of Plant Somatic Embryogenesis)

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18 pages, 4033 KiB

Open AccessArticle

Transcriptional and Metabolic Changes Associated with Phytoglobin Expression during Germination of Barley Seeds

by Somaieh Zafari, Kim H. Hebelstrup and Abir U. Igamberdiev

Int. J. Mol. Sci. 2020, 21(8), 2796; https://doi.org/10.3390/ijms21082796 - 17 Apr 2020

Cited by 16 | Viewed by 3317

Abstract

To understand how the class 1 phytoglobin is involved in germination process via the modulation of the nitric oxide (NO) metabolism, we performed the analysis of physiological and molecular parameters in the embryos of transgenic barley (Hordeum vulgare L. cv Golden Promise) plants differing in expression levels of the phytoglobin (Pgb1) gene during the first 48 h of germination. Overexpression of Pgb1 resulted in a higher rate of germination, higher protein content and higher ATP/ADP ratios. This was accompanied by a lower rate of NO emission after radicle protrusion, as compared to the wild type and downregulating line, and a lower rate of S-nitrosylation of proteins in the first hours postimbibition. The rate of fermentation estimated by the expression and activity of alcohol dehydrogenase was significantly higher in the Pgb1 downregulating line, the same tendency was observed for nitrate reductase expression. The genes encoding succinate dehydrogenase and pyruvate dehydrogenase complex subunits were more actively expressed in embryos of the seeds overexpressing Pgb1. It is concluded that Pgb1 expression in embryo is essential for the maintenance of redox and energy balance before radicle protrusion, when seeds experience low internal oxygen concentration and exerts the effect on metabolism during the initial development of seedlings. Full article

(This article belongs to the Special Issue Plant Respiration)

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