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Low temperature is a major environmental factor that affects metabolism, growth, development, distribution and production of chilling-sensitive plant, and J. curcas L. is a sustainable energy plant with great potential for biodiesel production due to the fact that its seed contains high oil content, which has attracted much attention worldwide. Our previous work found that the chill hardening improved the chilling tolerance of J. curcas seedlings (Ao et al. in Acta Physiologiae Plantarum 35:153–160, 2013), but its mechanism still remains elusive. In present work, the mechanism of chill hardening-induced chilling tolerance was further investigated in J. curcas seedlings. The results showed that chill hardening at 12 °C for 2 days markedly lowered osmotic and water potentials, which, in turn, maintained relative higher pressure potential in leaves of J. curcas seedlings compared with the control seedlings without chill hardening. In addition, chill hardening gradually increased compatible solutes proline, betaine and total soluble sugar contents compared with the control. When the control and hardened seedlings were subjected to chilling stress at 1 °C for 1–7 days, the chill-hardened seedlings significantly accumulated higher proline, betaine and total soluble sugar contents, which decreased osmotic and water potentials, and maintained higher pressure potential. To further understand the pathways of accumulation of compatible solutes, measurement of activities of ∆1-pyrroline-5-carboxylate synthetase (P5CS), glutamate dehydrogenase (GDH), ornithine aminotransferase (OAT), arginase, proline dehydrogenase (ProDH) and betaine dehydrogenase (BADH) showed that the chill hardening at 12 °C for 2 days obviously increased the activities of P5CS, GDH, OAT, arginase and BADH, as well as lowered ProDH activity both in leaves and stems of J. curcas seedlings to some extent as compared with the control. When the control and hardened seedlings were exposed to chilling stress at 1 °C for 1–7 days, the chill-hardened seedlings generally maintained significantly higher activities of P5CS, GDH, OAT, arginase and BADH. All above-mentioned results illustrated that the chill hardening could induce an accumulation of compatible solutes in leaves of J. curcas seedlings and compatible solutes play important roles in chill hardening-induced chilling tolerance.
Jatropha curcas L. is a sustainable energy plant with great potential for biodiesel production, and low temperature is an important limiting factor for its distribution and production. In this present work, chill hardeninginduced chilling tolerance and involvement of antioxidant defense system were investigated in J. curcas seedlings. The results showed that chill hardening at 10 or 12 C for 1 and 2 days greatly lowered death rate and alleviated electrolyte leakage as well as accumulation of the lipid peroxidation product malondialdehyde (MDA) of J. curcas seedlings under severe chilling stress at 1 C for 1–7 days, indicating that the chill hardening significantly improved chilling tolerance of J. curcas seedlings. Measurement of activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), and the levels of the antioxidants ascorbic acid (AsA) and glutathione (GSH) showed the chill hardening at 12 C for 2 days could obviously increase the activities of these antioxidant enzymes and AsA and GSH contents in the hardened seedlings. When the hardened and non-hardening (control) seedlings were subjected to severe chilling stress at 1 C for 1–7 days, the chill-hardened seedlings generally maintained significantly higher activities of the antioxidant enzymes SOD, APX, CAT, POD, and GR, and content of the antioxidants AsA and GSH as well as ratio of the reduced antioxidants to total antioxidants [AsA/(AsA ? DHA) and GSH/(GSH ? GSSG)], when compared with the control without chill hardening. All above-mentioned results indicated that the chill hardening could enhance the chilling tolerance, and the antioxidant defense system plays an important role in the chill hardening-induced chilling tolerance in J. curcas seedlings.
Low non-freezing temperature is one of the major environmental factors that affect metabolism, growth, development and geographical distribution of chilling-sensitive plants, Jatropha curcas, a chilling-sensitive plant, which is considered as a sustainable energy plant with great potential for biodiesel production. Our previous studies showed that short-term chilling shock at 5°C for 4 h and long-term chill hardening at 12°C 1 or 2 days could improve chilling tolerance of J. curcas seedlings, but lipidomic response to chilling shock and chill hardening has not been elucidated. In this study, membrane lipid composition change in J. curcas seedlings during chilling shock and chill hardening was investigated by liquid chromatography-electrospray ionization-mass spectrometry (LC–ESI–MS) approach. The results indicated that the relative abundances of nine classes and 72 species of membrane lipids, such as phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylinositol (PI), lysophosphatidylcholine (lysoPC) and lysophosphatidylglycerol (lysoPG), two glycolipids digalactosyldiacylglycerol (DGDG) and monogalactosyldiacylglycerol (MGDG) and a sulfoquinovosyldiacylglycerol (SQDG), were significantly changed, and the degree of unsaturation of above-mentioned cellular membrane lipids with fatty acid differing in chain lengths and the number of double bonds also increased in varying degrees during chilling shock and chill hardening. These results suggested that remodeling and increase in the degree of unsaturation of membranes lipids may be a common physiological basis for short-term chilling shock- and longterm chill hardening-induced chilling tolerance of J. curcas seedlings.
Hydrogen peroxide (H₂O₂), a second messenger, plays a vital role in seed germination and plant growth, development as well as the acquisition of stress tolerance, while hydrogen sulfide (H₂S) is considered as a new emerging cell signal molecule in higher plants. In the present study, soaking of H₂O₂ greatly improved germination percentage of Jatropha curcas seeds, stimulated the increase of L-cysteine desulfhydrase activity, which in turn induced accumulation of H₂S. On the contrary, pretreatment of aminooxyacetic acid (AOA), inhibitor of H₂S biosynthesis, eliminated H₂O₂ stimulated the increase of activity of L-cysteine desulfhydrase and accumulation of H₂S as well as improvement of germination percentage. In addition, exogenously applied H₂S also could improve germination percentage of seeds of J. curcas. These results suggested that pretreatment of H₂O₂ could improve germination percentage of J. curcas seeds and this improvement was mediated by H₂S.
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