Effect of root-applied spermidine on growth and respiratory metabolism in roots of cucumber (Cucumis sativus) seedlings under hypoxia
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The effects of exogenous spermidine (Spd) application to hypoxic nutrient solution on the contents of endogenous polyamines (PAs) and respiratory metabolism in the roots of cucumber (Cucumis sativus L.) seedlings were investigated. Cucumber seedlings were grown hydroponically in control and hypoxic nutrient solutions with and without addition of Spd at a concentration of 0.05 mM. The activities of key enzymes involved in the tricarboxylic acid cycle (TCAC), such as succinate dehydrogenase (SDH) and isocitrate dehydrogenase (IDH), were significantly inhibited under root-zone hypoxia with dissolved oxygen (DO) at 1 mg/l. In contrast, the activities of enzymes involved in the process of fermentation, such as pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and alanine aminotransferase (AlaAT), were significantly increased. Thus, aerobic respiration was inhibited and fermentation was enhanced in the roots of cucumber seedlings as a result of decreasing ATP content to inhibit the dry weight of seedlings under hypoxic stress. Moreover, the contents of free, soluble conjugated, and insoluble bound putrescine (Put), Spd, and spermine (Spm) in the roots of cucumber seedlings were significantly increased under hypoxia stress. Interestingly, application of Spd to hypoxic roots markedly suppressed the accumulation of free Put and, in contrast, promoted an increase in free Spd and Spm, as well as soluble conjugated and insoluble bound Put, Spd, and Spm contents. From these data, we deduced that exogenous Spd promotes the conversion of free Put into free Spd and Spm, and soluble conjugated and insoluble bound PAs under hypoxia stress. Furthermore, the activities of LDH, PDC, and ADH were suppressed and, in contrast, the activities of SDH and IDH were enhanced by application of exogenous Spd to hypoxic roots. As a result, aerobic respiration was enhanced but fermentation metabolism was inhibited in the roots of cucumber seedlings, leading to an increase in ATP content to alleviate the inhibited dry weight of seedlings due to hypoxia stress. These results suggest that application of Spd to hypoxic nutrient solution promoted conversion of free Put into free Spd and Spm as well as soluble conjugated and insoluble bound PAs, further enhanced IDH and SDH activities, and inhibited ethanol fermentation and lactate fermentation, resulting in increased ATP content and eventually enhanced tolerance of cucumber plants to root-zone hypoxia.
Key wordsCucumis sativus spermidine hypoxia growth polyamines
tricarboxylic acid cycle
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- 3.Roberts, J.K.M., Hooks, M.A., Miallis, A.P., Edwards, S., and Webster, C., Contribution of Malate and Amino Acid Metabolism to Cytoplasmic pH Regulation in Hypoxic Root Tips Studied Using Nuclear Magnetic Resonance Spectroscopy, Plant Physiol., 1992, vol. 98, pp. 480–487.CrossRefPubMedGoogle Scholar
- 6.Kasukabe, Y., He, L.X., Nada, K., Misawa, S., Ihara, I., and Tachibana, S., Overexpression of Spermidine Synthase Enhances Tolerance to Multiple Environmental Stresses and Up-Regulates the Expression of Various Stress-Regulated Genes in Transgenic Arabidopsis thaliana, Plant Cell Physiol., 2004, vol. 45, pp. 712–722.CrossRefPubMedGoogle Scholar
- 9.Ma, Y.H. and Guo, S.R., Classification and Hypoxia Stress Tolerance of Different Cucumber Cultivars, Jiangsu Agric. Sci., 2004, vol. 5, pp. 68–70.Google Scholar
- 10.Jia, Y.X., Guo, S.R., Li, J., Wang, S.P., Sun, J., and Huang, B.J., Effect of Exogenous Spd on Polyamines and Antioxidant System in Cucumber Seedlings under Hypoxia Stress, Acta Hortic. Sinica, 2007, vol. 34, pp. 1547–1550.Google Scholar
- 12.Zhang, W.H., Yu, B.J., Chen, Q., and Liu, Y.L., Tonoplast H+-ATPase Activity in Barley Roots Is Regulated by ATP and Pyrophosphate Contents under NaCl Stress, J. Plant Physiol. Mol. Biol., 2004, vol. 30, pp. 45–52.Google Scholar
- 14.Bergmeyer, H., Methods of Enzymatic Analysis, Weinheim: Verlag Chemie Press, 1983.Google Scholar
- 22.Jia, Y.X., Guo, S.R., Li, J., Sun, J., and Huang, B.J., Effects of Putrescine on Polyamines and Antioxidant System in Cucumber Seedlings under Root-Zone Hypoxia Stress, Acta Bot. Boreal-Occident. Sinica, 2008, vol. 28, pp. 1654–1662.Google Scholar
- 23.Mitsuya, Y., Takahashi, Y., Berberich, T., Miyazaki, A., Matsumura, H., Takahashi, H., Terauchi, R., and Kusano, T., Spermine Signaling Plays a Significant Role in the Defense Response of Arabidopsis thaliana to Cucumber Mosaic Virus, J. Plant Physiol., 2009, vol. 166, pp. 626–643.CrossRefPubMedGoogle Scholar
- 27.Zhao, F.G., Sun, C., Liu, Y.L., and Liu, Z.P., Effects of Salinity Stress on the Levels of Convalently and Non-convalently Conjugated Polyamines in Plasma Membrane and Tonoplast Isolated from Barley Seedling, Acta Bot. Sinica, 2000, vol. 42, pp. 920–926.Google Scholar