摘要或動機

Arabidopsis thaliana bZIPs（AtbZIPs）是一群影響層面相當廣泛的轉錄因子，一半以上的 AtbZIPs 基因表現受到光的調控，且近九成的分子機制尚未明瞭，因此探討 AtbZIPs 在植物光調控機制中所扮演的角色將是個有趣的課題。AtbZIP16 與 AtbZIP17 皆被推測會參與光的調控機制，然而迄今少有文獻針對這二個轉錄因子進行更多的研究。因此，我們想藉由細菌單雜合系統（Bacterial one hybrid system）的方法，找出能與 AtbZIP16 與 AtbZIP17轉錄因子結合的 DNA 序列，以瞭解此二轉錄因子調節下游基因表現的分子機制，並探討其在光訊息傳導途徑中所扮演的角色。針對 AtbZIP16 與 AtbZIP17，本實驗分別找到了 7 與10 種可能的結合序列。首先，經由資料庫比對分析，我們發現其序列上帶有的 motifs 功能，主要參與在光調控、環境逆境反應機制、組織發育、賀爾蒙調節、病原菌防禦、鈣離子訊息傳遞等方面，其中又以光調控佔最大的比例。再者，藉由將 motifs 的功能繪製成文氏圖，並與 HY5 （AtbZIP56）做比較，結果顯示，這三個轉錄因子雖同屬於 AtbZIP family，據推測皆受到光的調控，可能參與某些相似的生理調節過程，但都各自具備不同的功能，影響植物體的發育。如此的差異，表示他們有實質上的不同，值得我們更深入的研究。整體而言，本實驗結果除了說明 AtbZIPs 的功能確實廣泛之外，也顯示AtbZIP16 與AtbZIP17 是執行光訊號傳導很重要的調控因子。Arabidopsis thaliana bZIPs (AtbZIPs) is a group of transcription factors affecting a wide range of responses in Arabidopsis. The expression of more than half of the AtbZIPs is regulated by light, and the molecular mechanism for roughly 90% of these AtbZIPs remains unknown. Therefore, the roles AtbZIPs play in Arabidopsis light signal transduction is an interesting topic to pursue. AtbZIP16 and AtbZIP17 have been suggested to participate in the regulation mechanism mediated by light. However, only limited studies for these two transcription factors have been previously performed. For this reason, we intended to determine the DNA-binding sequences for AtbZIP16 and AtbZIP17 via the bacterial one hybrid system to reveal their target binding sites in the promoter region of their downstream genes and to speculate their possible biological function especially in light signal transduction pathway. We have identified 7 and 10 possible recognition sequences for AtbZIP16 and AtbZIP17, respectively. Using motif-finding programs analyses, we found the motifs identified are mainly involved in light and stress signaling, tissue development, hormone regulation, pathogen defense and Ca2+ signaling. Among these regulation pathways, sequences involved in light regulation owns the highest proportion. Furthermore, a Venn diagram was generated to compare functions of genes regulated by AtbZIP16, AtbZIP17 and HY5. Results revealed that, although these three transcription factors all belong to the AtbZIP family and are predicted to be regulated by some similar physiological regulation process (e.g. light), they still possess distict biological functions in plant development. Further studies are thus required to put these transcription factors into their shared and unique biological context. Taken together, the results of this experiment not only indicated light is a key regulation factor for AtbZIP16 and AtbZIP17, but also showed the function of AtbZIPs could be diverse.