比較水稻IR64耐旱突變系之生理反應及其相關基因表現

Comparison of Physiological Response and Relative Gene Expression of IR64 Drought-tolerant Rice mutant lines（Oryza sativa L.）

王泳傑(Yong-Jie Wang)

指導教授 ： 張孟基

共同指導教授 ： 林彥蓉

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02248

摘要

乾旱逆境影響水稻生長發育造成產量減少，乃至死亡。因此研究水稻乾旱逆境耐受性的反應機制並探討影響其耐受性的原因相當重要。本實驗以乾旱敏感的IR64及篩選出的IR64疊氮化鈉誘變系SM13以及SM47，進行乾旱逆境耐受性之生理反應及相關基因表現之比較。利用23.3% PEG水耕液所產生的高滲透勢模擬乾旱的條件，希望建立可用以鑑別水稻乾旱耐受性之有用生理指標。以葉片乾枯程度為傷害係數觀察到SM13、SM47比IR64有較好的外觀形態。在生理反應上包括相對水含量、光合作用效率、過氧化氫、MDA含量及葉部DAB染色過氧化氫，試驗顯示SM13、SM47亦有較佳之乾旱逆境耐受性。由於一般植物會以累積滲透調控物質方式適應乾旱逆境，因此探討逆境下地上部、地下部脯胺酸的累積現象，以及地上部可溶糖類累積，但結果只有根部脯胺酸含量與觀察到的耐旱結果一致。而逆境下抗氧化酵素SOD的活性上，以SM47有較高活性，而在SM13提升則較為平緩。最後分析乾旱耐受性相關基因之表現，發現除了SM13的OsSNAC1不受影響，其OsNAC6、OsSNAC1基因都受到誘導。此外調控類胡蘿蔔素合成基因DSM2在SM47中受到誘導，可藉此影響離層酸合成以及影響離層酸下游調控基因反應。而轉錄因子OsbZIP23在SM13、SM47受PEG誘導調控，趨勢與ABA相關基因OsDREB2A一致，顯示兩突變系可經由轉錄因子之調控，引發下游乾旱耐受反應。此外PEG處理亦誘導SM13、SM47脯胺酸合成基因OsP5CS1及OsP5CS2之表現，尤其在OsP5CS2，而SM47的OsOAT之所以受到誘導現象，可能藉由OsSNAC2/OsNAC6調控下游基因OsOAT引發由粒線體中合成脯胺酸的途徑，藉著累積脯胺酸一方面維持滲透勢一方面調節氧化還原。總而言之，SM13及SM47突變系對於PEG逆境下可能透過基因調控進而累積較多脯胺酸，維持滲透壓，同時也保護氧化還原的平衡，使得逆境下得以維持相對水含量，維持較高光合效率，造成較好的乾旱耐受性。

關鍵字

水稻 ； 乾旱逆境耐受性 ； 叠氮化鈉 ； IR64 ； 生理反應 ； 脯胺酸 ； 可溶糖 ； 基因表現

並列摘要

Drought stress affects rice (Oryza sativa) growth, reduces yield and even causes death. Thus, it is very important to understand the physiological mechanism related to rice drought stress response and tolerance. This study aims to compare the physiological responses and gene expressions among sensitive variety IR64, and its sodium azide-mutant lines SM13、SM47 under PEG treatment. The results showed that based on the damage score of leaf driness level, SM13 and SM47 appeared to have better tolerant morphology under stress. Similar results were obtained using other physiological assay, including relative water content, photosynthesis efficiency, H2O2 content, MDA content and in situ H2O2 staining. Since most plants accumulate osmolytes to adapt the drought stress, the proline accumulation in the whole plant and total soluble sugars content in the shoot were also investigated. However, only the proline content in SM47 root was correlated with the extent of drought tolerance. Besides, SM47 showed relative high antioxidant enzyme SOD activity while SM13 did not change the enzymatic activity. We also examined the genes expression profile of many drought tolerant related genes, the result indicated that OsNAC6 and OsSNAC1 gene induced wilthin all rice lines, but OsSNAC1 induced specifically in SM13. DSM2 gene, involved in controlling the xanthophylls synthesis, was increased in SM47, which may influence the ABA synthesis and downstream regulation response. In addition, SM13 and SM47 seem to be able to regulate the drought tolerance downstream response by inducing the expression of drought responsive related transcription factors, OsbZIP23 and OsDREB2A. Meanwhile, the expression of OsP5CS1 and OsP5CS2, two proline synthesis genes, were also induced by stress. In SM47, the proline may be accumulated by OsNAC6 which regulate the downstream gene encode OsOAT, then stimulate the proline synthesis in mitochondria. To sum up, the SM13 and SM47 showed better drought tolerance by regulating the gene expression related to the accumulation of proline, which maintains the osmolality, adjusting the homeostasis of the reduction-oxidation status and retains the water content.

並列關鍵字

rice (Oryza sativa L.) ； drought stress tolerance ； sodium azide ； IR64 ； physiological response ； proline ； soluble sugar ； gene expression

參考文獻

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