The role of proline synthesis enzymes under stresses via virus-induced gene silencing in tobacco
| Autor: | Chih-Chieh Hu, 胡智傑 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Proline accumulation is wide spread phenomenon in stressed plants. Proline could be synthesized with Δ1-pyrroline-5-carboxylate synthetase (P5CS) from glutamate and with ornithine-δ-aminotransferase (OAT) from ornithine in plants. It dose don not know well about the role of P5CS and OAT in stressed plants. The aim of this thesis is to investigate which enzyme is more important for proline synthesis, and what is the possible function of these enzymes in response to abiotic stress. We used Tobacco mosaic virus (TMV) as vector with the insertion of proline metabolized related gene fragments to decrease the expression of P5CS (TMV-antiP5CS), OAT (TMV-antiOAT), or both of P5CS and OAT (TMV-antiP5CS＋antiOAT) in 10 weeks old tobacco via the mechanism of VIGS (virus-induced gene silencing). The tobacco leaf discs taking form first and second leaf above the inoculated leaf were treated with 29％PEG (polyethylene glycol), 100 μM abscisic acid (ABA), or 50 μM CdCl2 to mimic three abiotic stresses. Under PEG treatment, the proline level of tobacco leaf discs inoculated with TMV-P5CS or TMV-OAT decreased about 80-90％ and 5-15％ respectively. The changes of proline level under ABA or Cd treatment were similar to PEG treatment. It is suggests that P5CS could be the major enzyme for proline accumulation under heavy metal stress. In order to investigate the possible function of P5CS and OAT expression in stressed plant, the chlorophyll and MDA content of leaf discs treated with VIGS were analyzed. The degradation of chlorophyll in TMV-antiP5CS inoculated tobacco leaf discs was faster than in TMV-GFP under PEG treatment. But the degradation in TMV-antiOAT was slower than in TMV-GFP. There was no difference in MDA content among all VIGS treated plant under stresses. It is noticed that the content of polyamine increased in TMV-antiOAT inoculated tobacco leaf discs under osmotic stress. In summary, P5CS is the major enzyme of proline accumulation under osmotic stress, ABA or heavy metal stress. OAT participates the proline accumulation only in osmotic stress. Under osmotic stress, inhibiting P5CS pathway can improve the rate of chlorophyll degradation. But inhibiting OAT pathway can delay the rate of chlorophyll degradation that migh be related to the increase of polyamine content in tobacco leaf discs. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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