阿拉伯芥鋅手指蛋白3受熱休克轉錄因子調控並作為抑制子調控熱休克反應

Abstract

熱逆境代表溫度高於生物適合生長的溫度，並會導致植物的生長與發育受到影響並減少，有時甚至能導致植物死亡。為了生存，植物發展出了一套機制來對抗熱逆境以提升自己的存活率，這個機制被稱為熱逆境反應(heat stress response, HSR)，在該機制中，透過熱休克轉錄因子的調控，生物體內會累積熱休克蛋白(heat shock protein, HSP)來保護自己免受熱逆境的影響。在之前的研究中，我們報導了一種特殊的熱休克轉錄因子A6b (HSFA6b)透過離層酸(ABA)調控了植物的熱逆境反應。在該實驗的微陣列晶片資料顯示中，我們偵測到了一個鋅手指蛋白轉錄因子鋅手指蛋白3 (Zinc protein 3, ZF3)被認為是受到HSFA6b調控。這裡我們將描述ZF3在熱逆境下的調控機制與功能，我們的實驗證實了ZF3會受到熱逆境的誘導並且作用在細胞核中。而ZF3的調控則受到熱休克轉錄因子間交互網路的影響，其中，HSFA3和HSFA6b是最影響其表現的調控者，除了此二者之外，其他的熱休克轉錄因子例如HSFA1b和HSFA4也會影響其表現量並且有可能是透過乾旱反應結合序列蛋白(DREB)與HSFA3來調控其表現量。另外一方面，剔除ZF3的阿拉伯芥在獲得性耐熱反應中會有更好的耐熱能力，這告訴我們ZF3的功能應該是熱逆境反應的抑制因子，其他實驗中，我們進一步調查了熱逆境反應基因在熱逆境下被ZF3影響的情形，並證實了ZF3能抑制sHSP和氧化逆境基因APX2的表現量。這告訴我們ZF3是一個受熱誘導表現在細胞核內並作為抑制因子調控熱逆境反應的基因。

Heat stress (HS) refers to temperatures above the optimum growth temperatures for organisms. This stress can lead plants to experience severe retardation in growth and development, and in extreme cases cause death. In order to survive, a conserved mechanism of heat stress responses (HSR) is developed to accumulate heat shock proteins (HSPs) to protect plants via a group of transcription factors called heat shock factors (HSFs). In our previous study, we reported that a special Arabidopsis HSF HSFA6b regulates the HSR via the ABA-dependent pathway. In the heat response microarray data, we detected a zinc protein transcription factor Zinc Finger 3 (ZF3) which was suggested to be regulated under HSFA6b. Here, we describe the regulation and function of ZF3 under HS. Our investigation shows that the expression of ZF3 is induced by heat stress and ZF3 is localized to the nucleus. ZF3 regulation is influenced by the complex network of HSFs; our data shows that ZF3 is strongly regulated by HSFA3 and HSFA6b while other HSFs such as HSFA1b may also influence the regulation of ZF3 via the DREB-HSFA3 pathway. In addition, ZF3 knockout mutants displayed increased thermotolerance as compared with the WT for acquired thermotolerance; this indicated that ZF3 is a repressor in HSR. Further investigation of gene expression showed that ZF3 can repress the expression of sHSPs and of antioxidant gene APX2. Thus, we report that ZF3 is a heat induced transcription factor that was confirmed to be localized in the nucleus, and functions as a HSR negative regulator in Arabidopsis.