水稻葉片老化之研究：脫落酸與甲基茉莉酸鹽之效應

Studies on the Senescence of Rice Leaves: Effects of Abscisic Acid and Methyl Jasmonate

洪國棟(Kuo Tung Hung)

指導教授 ： 高景輝

國立臺灣大學/生物資源暨農學院/農藝學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.00002

摘要

本論文係探討脫落酸 (abscisic acid，ABA) 與甲基茉莉酸鹽 (methyl jasmonate，MJ) 促進水稻切離葉片老化之可能機制。研究結果簡述如下：
(一) 照光下，一氧化氮釋放劑可克服巴拉刈 (paraquat，PQ) 所引起水稻切離葉片之毒害、malondialdehyde (MDA) 含量增加與抗氧化酵素活性之降低。黑暗下，過氧化氫所引起之水稻切離葉片老化 (蛋白質含量降低做為指標)、MDA 含量增加、抗氧化物 [ascorbic acid (AsA) 與還原態 glutathione (GSH)] 含量降低以及抗氧化酵素比活性之增加，亦可被一氧化氮釋放劑所克服。一氧化氮清除劑 carboxy-2-phenyl-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxide 處理可使一氧化氮釋放劑對 PQ 與過氧化氫的保護作用消失，顯示一氧化氮釋放劑之作用是由其釋放出的一氧化氮所造成。一氧化氮釋放劑之作用主要是清除活化氧族。
(二) 自由基清除劑 (sodium benzoate 與 GSH) 與一氧化氮釋放劑可抑制 ABA 與 MJ 所促進水稻葉片老化、脂質過氧化作用與過氧化氫含量增加、抗氧化酵素比活性增加、抗氧化物含量降低，說明 ABA 與 MJ 所促進之水稻葉片老化係經由氧化逆境。
(三) 對 diphenyleneiodonium (DPI) 與 imidazole (IMD) 敏感的 NADPH oxidase 與對 KCN 與 NaN3 敏感的 peroxidase 是 ABA 與 MJ 促進水稻葉片形成過氧化氫之主要酵素。
(四) Phosphatidylinositol 3-kinase 之抑制劑 LY 294002 (LY) 與wortmannin (WM) 可抑制 ABA 與 MJ 所誘導的水稻葉片過氧化氫形成與老化，顯示 NADPH oxidase 之活化需要 phosphatidylinositol 3-phosphate 之參與。
(五) 過氧化氫形成抑制劑 (DPI、IMD、KCN、NaN3、LY 與 WM) 與過氧化氫捕捉劑 (dimethylthiourea) 能夠抑制 ABA 與 MJ 所促進之葉片老化以及銨離子與花青素之累積。顯示 ABA 與 MJ 之作用需要過氧化氫參與。
(六) 氯化鈣與鈣離子通道劑 A23187 可有效抑制 ABA、MJ 與過氧化氫所促進之葉片老化，顯示 ABA、MJ 與過氧化氫之作用是經由抑制鈣離子運移到細胞質。

關鍵字

脫落酸 ； 甲基茉莉酸鹽 ； 水稻 ； 老化

並列摘要

In this dissertation, we studied the possible mechanism of abscisic acid (ABA)- and methyl jasmonate (MJ)-promoted senescence of detached rice leaves. The main results are outlined as follows:
1. Nitric oxide (NO) donors prevented paraquat (PQ)-induced toxicity, PQ-increased MDA content and PQ-decreased antioxidative enzyme activities in detached rice leaves in the light. NO donors were also effective in reducing hydrogen peroxide-induced senescence, hydrogen peroxide-induced lipid peroxidation, hydrogen peroxide-decreased antioxidant [ascorbic acid (AsA) and reduced glutathione (GSH)] contents, and hydrogen peroxide-increased antioxidative enzyme specific activities in rice leaves under dark condition. The protective effect of NO donors on PQ- and hydrogen peroxide-induced responses was reversed by carboxy-2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, indicating that the protection effect of NO donors is attributable to NO released. The effect of NO donors is mediated through its ability to scavenge reactive oxygen species.
2. Free radical scavengers (sodium benzoate and GSH) and NO donors reduced ABA- and MJ-induced senescence, ABA- and MJ-increased malondialdehyde (MDA) and hydrogen peroxide contents, antioxidative enzyme specific activities, and ABA- and MJ-decreased antioxidant contents of detached rice leaves. It seems ABA- and MJ-promoted senescence of detached rice leaves is mediated through oxidative stress.
3. NADPH oxidase, which is sensitive to diphenyleneiodonium (DPI) and imidazole (IMD), and peroxidase (POD), which is sensitive to KCN and NaN3, are two enzymes responsible for hydrogen peroxide production in rice leaves treated with ABA and MJ.
4. Phosphatidylinositol 3-kinase inhibitors LY 294002 (LY) and wortmannin (WM) inhibited ABA- or MJ-induced hydrogen peroxide production and senescence of rice leaves, suggesting that phosphatidylinositol 3-phosphate is required for NADPH oxidase activation.
5. Inhibitors of hydrogen peroxide production (DPI, IMD, KCN, NaN3, LY, and WM) and chemical trap for hydrogen peroxide (dimethylthiourea) were able to reduce ABA- and MJ-promoted senescence and accumulation of ammonium ions and anthocyanins, suggesting that hydrogen peroxide is involved in ABA- and MJ-promoted senescence and accumulation of ammonium ions and anthocyanins of rice leaves.
6. CaCl2 and A23187, calcium ionophore, were effective in preventing ABA-, MJ- and hydrogen peroxide-promoted senescence and accumulation of ammonium ions and anthocyanins of rice leaves, suggesting the effect of ABA, MJ, and hydrogen peroxide is mediated through blocking the entrance of Ca2+ into cytosol.

並列關鍵字

methyl jasmonate ； rice ； senescence ； abscisic acid

參考文獻

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