轉錄因子bZIP16參與調控阿拉伯芥幼苗發育的分子機制研究

植物無法自由移動，因此必需不斷的適應外在環境的改變以維待適當的生長。光是影響植物生長與發育重要的環境因子之一。以阿拉伯芥為例，光明顯的調控其每一個生長階段。為了感應不同光強度及光質，並適時傳遞光訊息，阿拉伯芥藉由不同的光受器及轉錄因子調控下游基因的表現，以進行光形態發育。在受光所調控的基因中，在其啟動子位置常常具有能被特定轉錄因子所結合的G-box DNA保守序列。在本論文中，我利用G-box DNA親合層析法(DNA affinity chromatography)，找到一個含有basic region/leucine zipper motif的轉錄因子-bZIP16。藉由基因的功能性分析及分子機制的研究發現：bZIP16參與調控植物受光影響的數個生長階段。在種子發芽和幼苗去白化的生長時期，bZIP16主要能負調控光、吉貝素(gibberellic acid)和離層酸(abscisic acid)訊號傳遞的基因，以促進種子的發芽以及幼苗下胚軸的延長。在幼苗及營養生長時期，不同紅/遠紅光的比例會決定bZIP16蛋白質的穩定性。本論文指示，bZIP16蛋白質可與阿拉伯芥光受器光敏素B (phytochrome B)結合，並在細胞核中形成nuclear body。在高紅/遠紅光比例的光條件下，bZIP16與phytochrome B的結合會促進bZIP16藉由26S蛋白酶體(26S proteasome)進行蛋白質降解，以減緩在低紅/遠紅光比例的光條件下，藉由bZIP16促進下胚軸與葉柄延長的光遮避效應。本研究不僅發現bZIP16參與阿拉伯芥幼苗的生長發育和光遮避效應，研究結果並闡述bZIP16在這些重要生理反應中的分子作用機制，也為未來相關研究開啟一個全新的方向。

關鍵字

光敏素； bZIP16 ；吉貝素；離層酸；種子萌芽；下胚軸延長； 26S蛋白酶體；光遮避效應

並列摘要

Plants are sessile organisms and need to adapt to the ever-changing environment for optimal growth and development. Light is one such environmental factor. In Arabidopsis, almost its entire life cycle is influenced by the light signals. Key regulators for plants to perceive and coordinate the environmental signals include photoreceptors and signaling molecules, especially transcription factors. In this thesis, a basic region/leucine zipper motif transcription factor, bZIP16, was identified by its affinity to G-box commonly present in many light-responsive genes. My study indicated that bZIP16 plays important roles in multiple light-mediated growth and developmental stages in Arabidopsis. In seed germination and seedling de-etiolation stages, bZIP16 primarily represses the expression of light-, gibberellic acid (GA)- and abscisic acid (ABA)-responsive genes, resulting the promotion of seed germination and hypocotyl elongation. In the seedling and vegetative stages, the red/far-red light ratios determine differential stability of the bZIP16 protein. My study indicated that bZIP16 interacts with photoreceptor phytochrome B and is localized in nuclear body. High red/far-red rations triggers the 26S proteasome-mediated degradation of bZIP16, compromising its positive role in promoting hypocotyl and petiole elongation in shade-avoidance responses under low red/far-red light conditions. Studies in this thesis not only demonstrated that bZIP16 participates in a wide spectrum of light-regulated responses, but also provided conclusions on its action mechanisms. The findings laid a solid foundation for future in-depth studies of bZIP16 in Arabidopsis light signaling transduction.

並列關鍵字

phyB ； bZIP16 ； gibberellic acid (GA) ； abscisic acid (ABA) ； seed germination ； hypocotyl elongation ； 26S proteasome ； shade-avoidance responses

參考文獻

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國際替代計量

轉錄因子bZIP16參與調控阿拉伯芥幼苗發育的分子機制研究

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