chlorophyll-a and Magnesium-Deficiency

Topics: Chlorophyll; Chlorophyll A; Gene Expression Profiling; Magnesium; Magnesium Deficiency; Oxidoreductases; Plant Leaves; Transcriptome

Magnesium (Mg) is an essential macronutrient for plant growth and development. Physiological and transcriptome analyses were conducted to elucidate the adaptive mechanisms to long-term Mg deficiency (MD) in banana seedlings at the 6-leaf stage. Banana seedlings were irrigated with a Mg-free nutrient solution for 42 days, and a mock control was treated with an optimum Mg supply. Leaf edge chlorosis was observed on the 9th leaf, which gradually turned yellow from the edge to the interior region. Accordingly, the total chlorophyll content was reduced by 47.1%, 47.4%, and 53.8% in the interior, center and edge regions, respectively, and the net photosynthetic rate was significantly decreased in the 9th leaf. Transcriptome analysis revealed that MD induced 9,314, 7,425 and 5,716 differentially expressed genes (DEGs) in the interior, center and edge regions, respectively. Of these, the chlorophyll metabolism pathway was preferentially enriched according to Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The expression levels of the five candidate genes in leaves were consistent with what is expected during chlorophyll metabolism. Our results suggest that changes in the expression of genes related to chlorophyll synthesis and decomposition result in the yellowing of banana seedling leaves, and these results are helpful for understanding the banana response mechanism to long-term MD.

Topics: Chlorophyll; Gene Expression Profiling; Gene Expression Regulation, Plant; Magnesium Deficiency; Musa; Plant Leaves; Seedlings; Transcriptome

Magnesium (Mg) is an essential metal for chlorophyll biosynthesis and other metabolic processes in plant cells. Mg is largely stored in the vacuole of various cell types and remobilized to meet cytoplasmic demand. However, the transport proteins responsible for mobilizing vacuolar Mg2+ remain unknown. Here, we identified two Arabidopsis (Arabidopsis thaliana) Mg2+ transporters (MAGNESIUM TRANSPORTER 1 and 2; MGT1 and MGT2) that facilitate Mg2+ mobilization from the vacuole, especially when external Mg supply is limited. In addition to a high degree of sequence similarity, MGT1 and MGT2 exhibited overlapping expression patterns in Arabidopsis tissues, implying functional redundancy. Indeed, the mgt1 mgt2 double mutant, but not mgt1 and mgt2 single mutants, showed exaggerated growth defects as compared to the wild type under low-Mg conditions, in accord with higher expression levels of Mg-starvation gene markers in the double mutant. However, overall Mg level was also higher in mgt1 mgt2, suggesting a defect in Mg2+ remobilization in response to Mg deficiency. Consistently, MGT1 and MGT2 localized to the tonoplast and rescued the yeast (Saccharomyces cerevisiae) mnr2Δ (manganese resistance 2) mutant strain lacking the vacuolar Mg2+ efflux transporter. In addition, disruption of MGT1 and MGT2 suppressed high-Mg sensitivity of calcineurin B-like 2 and 3 (cbl2 cbl3), a mutant defective in vacuolar Mg2+ sequestration, suggesting that vacuolar Mg2+ influx and efflux processes are antagonistic in a physiological context. We further crossed mgt1 mgt2 with mgt6, which lacks a plasma membrane MGT member involved in Mg2+ uptake, and found that the triple mutant was more sensitive to low-Mg conditions than either mgt1 mgt2 or mgt6. Hence, Mg2+ uptake (via MGT6) and vacuolar remobilization (through MGT1 and MGT2) work synergistically to achieve Mg2+ homeostasis in plants, especially under low-Mg supply in the environment.

Topics: Acclimatization; Arabidopsis; Arabidopsis Proteins; Calcineurin; Carrier Proteins; Chlorophyll; Gene Expression Regulation, Plant; Humans; Magnesium; Magnesium Deficiency; Manganese; Membrane Transport Proteins; Saccharomyces cerevisiae; Vacuoles

Magnesium (Mg) is a relatively mobile element that is remobilized in plants under Mg-limited conditions through transport from old to young tissues. However, the physiological and molecular mechanisms underlying Mg remobilization in plants remain poorly understood. In this study, we investigated Mg remobilization in rice (

Topics: Biological Transport; Chlorophyll; Chloroplasts; Gene Expression Regulation, Plant; Magnesium; Magnesium Deficiency; Oryza; Phenotype; Photosynthesis; Plant Leaves; Plant Proteins; Reactive Oxygen Species; Signal Transduction

180 days old Dimocarpus longana seedlings were grown in nutrition solution with three magnesium concentrations as 4 mmol.L-1 Mg2+ (sufficient supply), 0.4 mmol.L-1 Mg2+ (deficient supply), and Mg-free (without supply). Leaves were sampled 120 and 150 days later after treatment. With an increase in severity of Mg-deficient, the chlorophyll content, PS II activities, photosynthetic rate, protein, nucleic acid (DNA, RNA), and ZRs contents declined progressively. Whereas the content of H2O2, the rate of O2-. generation as well as the content of malondialdehyde (MDA) increased. The results suggested that magnesium deficiency had significant effect on the senescence of Dimocarpus longana leaves.

Topics: Aging; Chlorophyll; Down-Regulation; Hydrogen Peroxide; Light-Harvesting Protein Complexes; Magnesium Deficiency; Malondialdehyde; Photosynthetic Reaction Center Complex Proteins; Plant Growth Regulators; Plant Leaves; Reactive Oxygen Species; Sapindaceae; Up-Regulation

The growth of photoautotrophic Euglena gracilis Z is strongly inhibited by manganese deficiency, whereas chlorophyll formation is not appreciably affected. The galactosyldiglyceride content of the manganese-deficient photo-autotrophic Euglena was about 40% lower on the basis of either chlorophyll content or dry weight. When dark-grown cultures of Euglena were grown photoheterotrophically in light sufficient for the greening of the cells, or photosynthesis, manganese deficiency resulted in a reduction of the cellular content of chlorophyll and galactosyldiglycerides to 40% of control values, indicating interference with chloroplast formation. The fatty acids of the photoheterotrophic manganese-deficient cells were mainly saturated, with an unusual accumulation (about 45%) of the total fatty acids) of myristic acid. In spite of this, the galactosyldiglycerides contain mainly unsaturated fatty acids. Ninety per cent of the fatty acids of the monogalactosyldiglyceride are unsaturated, including large amounts of alpha-linolenic acid. The ratio of chlorophyll to galactosyldiglyceride content of the cells was remarkably constant at all manganese deficiency levels.

Topics: Chlorophyll; Euglena; Fatty Acids; Glycerides; Lipid Metabolism; Magnesium Deficiency; Photosynthesis