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標題: | 水稻品系Pokkali抗淹水逆境之調控機制 Mechanism of Submergence Tolerance in Pokkali Rice |
作者: | Hsiang Hsieh 謝湘 |
指導教授: | 施明哲(Ming-Che Shih) |
關鍵字: | 水稻,淹水耐受性,SUB1A-1,吉貝素,轉錄調控, gibberellin,rice,submergence tolerance,SUB1A-1,transcriptional regulation, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | SUBMERGENCE1A-1 (SUB1A-1)是第七群乙烯反應轉錄因子(group-Vll ethylene response transcription factor, ERF-Vll)之一,在某些水稻品系的抗淹水逆境中扮演十分重要的角色,例如:FR13A和Pokkali。遭遇淹水時,SUB1A-1在FR13A中大量被誘導,且FR13A的生長會受到延遲,以利淹水期間節省能量消耗,直至水退後甫進行生長,此策略稱為low oxygen quiescence syndrome (LOQS)。雖然Pokkali水稻同樣具有SUB1A-1,但卻在淹水逆境中採取截然不同的策略。與FR13A相較之下,SUB1A-1的表現量在Pokkali中只受到淹水少量誘導,且Pokkali的生長並不會受到淹水的影響。從基因微陣列(microarray)分析結果發現,在淹水期間有一群負責將活化態GA轉換成非活化態的GA2 OXIDASE基因在Pokkali中有相對較低的誘導表現。另外,我們也發現GA下游的基因EXPANSIN在Pokkali中則有相對較高的誘導表現。進一步檢查在淹水期間三種水稻品系中活化態GA的變化情形,結果顯示,遭遇淹水後活化態GA會在Pokkali中逐漸累積,但在FR13A中並沒有明顯的變化。我們進一步發現大量的活化態GA使得SUB1A-1的表現受到抑制。另外,益收水溶液處理顯示,乙烯在淹水期間可能促進GA調控的下游反應,以利淹水期間植株得以持續生長。另一方面,我們也發現淹水逆境時,與FR13A相較之下,HEMOGLOBIN、ACYL-ACP DESATURASE、CLC7和HAK1基因在Pokkali中有較高的誘導表現。因此,根據實驗結果,我們推測淹水期間在Pokkali此種水稻品系中,乙烯促進GA調控的下游反應以及誘導少量的SUB1A-1表現,另一方面,大量累積的活化態GA進一步抑制了SUB1A-1的表現,使得SUB1A-1在Pokkali中維持較低的表現量。除此之外,我們也推測除了SUB1A-1之外,還有其他的因子在Pokkali的抗淹水逆境中參與了重要的調控。根據基因微陣列分析結果,我們找出可能調控Pokkali淹水耐受性的基因,包括了HEMOGLOBIN、ACYL-ACP DESATURASE、CLC7以及HAK1,這些基因尚需進一步的實驗加以驗證。
另一方面,先前研究指出同屬於第七群乙烯反應轉錄因子的ERF66和ERF67的表現量可能會受到SUB1A-1的調控。透過啟動子轉錄分析(trans-activation assay)實驗,我們發現SUB1A-1蛋白正向調控ERF66與ERF67的表現。另外,SUB1A-1基因本身的表現同樣也會受SUB1A-1蛋白的活化,有趣的是,此活性並不是透過SUB1A-1蛋白結合在SUB1A-1基因啟動子上已知的第七群乙烯反應轉錄因子結合序列GCC box,而是可能透過結合啟動子上其他的順式調控元素(cis-element)來調控其活化。根據以上實驗結果,我們推測在淹水期間,SUB1A-1蛋白透過活化本身SUB1A-1基因表現以及誘導下游ERF66與ERF67的表現量,來參與水稻抗淹水逆境的調控,給予水稻對於淹水的耐受性。 SUBMERGENCE1A-1 (SUB1A-1) is a member of the group-Vll ethylene response transcription factors (ERF-Vlls) which confers major flooding-tolerance to some rice cultivars, including FR13A and Pokkali. Encountering submergence stress, FR13A shows a “low oxygen quiescence syndrome (LOQS)” phenotype, including: 1) the transcription level of SUB1A-1 is highly up-regulated and 2) the growth of FR13A is retarded until the water subsided. Although possessing SUB1A-1 as well, Pokkali displays a contrasting flooding-tolerant phenotype. Pokkali has a much lower induction level of SUB1A-1 than that of FR13A and continues to grow under submergence. Microarray data showed that some GA2 OXIDASEs encoding enzymes that catalyze active GA to inactive forms were lowly induced in Pokkali than in FR13A during submergence. Additionally, a series of EXPANSINs, which are GA-responsive genes, had much higher induction levels in Pokkali. GC/MS analysis indicated that the level of GA4 is highly increased in Pokkali under submergence, but not changed in FR13A. Furthermore, GA3 and ethephon treatments revealed that high levels of GA inhibited the expression of SUB1A-1 under submergence, and ethylene could promote GA response in rice, respectively. Moreover, a number of genes were highly induced in Pokkali than in FR13A under submergence, including HEMOGLOBIN, ACYL-ACP DESATURASE, CLC7 and HAK1, which may contribute to submergence tolerance of Pokkali. Based on these results, we hypothesized that in Pokkali ethylene triggers higher GA accumulation, which represses SUB1A-1 induction at lower levels. HEMOGLOBIN, ACYL-ACP DESATURASE, CLC7 and HAK1, which were highly induced in Pokkali than in FR13A under submergence, might participate in submergence tolerance of Pokkali. Furthermore, prior studies showed that ERF66 and ERF67, members of ERF-Vlls, might be regulated by SUB1A-1. Through trans-activation assays, we proved that SUB1A-1 not only positively regulated the transcription of ERF66 and ERF67, but also activated itself at the transcription level. It is possible that SUB1A-1 binds other cis-element at the SUB1A-1’s promoter other than GCC box, which conferred flooding tolerance to rice by activating itself at the transcription level and enhanced the transcription of downstream targets, including ERF66 and ERF67. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20851 |
DOI: | 10.6342/NTU201700828 |
全文授權: | 未授權 |
顯示於系所單位: | 植物科學研究所 |
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