- 學位論文
南西文心蘭鈉氫離子反向運輸蛋白OgNHX1及OgNHX6之功能性探討
Functional study of Na+/H+ exchangers OgNHX1 and OgNHX6 from Oncidium Gower Ramsey
摘要
本研究以南西品系文心蘭作為材料，探討的鈉氫離子反向運輸蛋白 (NHX, Na+/H+ exchanger) 是否參與了文心蘭對抗滲透壓逆境的分子機制。NHX為植物細胞中重要的離子運輸蛋白。可以交換等量正一價的陽離子以及氫離子穿過細胞的膜狀構造。其位置可能在液胞膜、高基氏體或是細胞膜上，並參與細胞內pH值調節、鉀離子及鈉離子的平衡，因此與植物對滲透壓逆境的耐受性有關。目前NHX已經被成功轉殖至多種作物，並改善植物對於鹽鹼環境的耐受性。文心蘭則為台灣重要的切花外銷作物，在自然環境中為附生性植物 (epiphyte)，對於滲透壓逆境有著相當高的耐受性。 我們首先從南西文心蘭的基因轉錄體資料庫中 (transcriptome database)中釣取兩條NHX核酸序列並命名為OgNHX1以及OgNHX6。藉由RT-PCR以及realtime-PCR檢測，發現這兩個基因在文心蘭的各個部位皆有相近的表現量。OgNHX1和OgNHX6的表現量不會受到外加鹽逆境或是過氧化氫的誘導，但在幼年時期的組織表現量較高。接著我們釣取這兩個基因的啟動子，並掛載報導基因轉入阿拉伯芥。發現轉植株的GUS活性在幼年阿拉伯芥活性較強，且會受到外加鹽逆境的誘導，最後我們也將OgNHX1以及OgNHX6轉入阿拉伯芥大量表現。雖然轉植株的根長和側根數有些微的減少，但外表型和耐鹽性皆與對照組無顯著差異。因此推測OgNHX1和OgNHX6的生理功能和過去報導能夠對抗鹽逆境的NHXs有所不同
並列摘要
Oncidium Gower Ramsey is one of the most important horticulture export product in Taiwan. Most of species from Orchidaceae family, including Oncidium Gower Ramsey, are originated in tropical areas Thus they have several special structures corresponding to drought environments. Plant constantly challenged by external abiotic stress including drought, cold and salinity. In order to adapt to osmotic unbalance resulted from these abiotic stresses, plant evolved several special mechanisms to adjust its internal ion distribution such as NHXs cation/H+ antiporters. In previous studies, NHXs had considered as important regulators in respond to salinity stress. We identified two putative NHX genes from Oncidium Gower Ramsey named “OgNHX1” and “OgNHX6”. These two genes expressed equally in different parts of Oncidium tissues, and surprisedly, unchanged under external salt or hydrogen peroxide treatment. The phenotypes of transgenic Arabidopsis overexpressing OgNHX1/6 showed no differentces comparing to wild-type plants when grown in salnity environment. However the results from stage-dependent realtime-PCR and promoter-GUS analysis suggest possible connections between OgNHXs and plant development. Our results suggest the functions of OgNHX1 and OgNHX6 are atypical to pervious studies, in which consider NHXs as efficient candicates to generate salt-tolerant plants.