BASIC PENTACYSTEINE對阿拉伯芥發育分子機制之影響研究

Abstract

植物體內的「生物時鐘 (circadian clock) 」能藉由接受光照時間與外界溫度的規律變化來感知日夜週期的節律，使得植物因應瞬息萬變的環境時，仍能維持在最適當的季節生長與發育。BASIC PENTACYSTEINE (BPC)家族是植物特有的轉錄因子，已知缺乏BPCs時在生長與發育過程中會產生多重的缺陷。先前研究顯示BPC 成員BPC1、BPC2、BPC4和BPC6會共同拮抗BPC3。本研究中藉由分析BPC3 在bpc1-1 bpc2 bpc4 bpc6 (bpc1246)四重突變株中的表現發現其轉錄產物累積變高，進一步檢測阿拉伯芥生物時鐘核心基因的表現，發現CCA1、PRR9、PRR7、 PRR5、PRR3、ELF4、TOC1表現相位明顯延遲，時鐘下游光週期開花途徑的CO表現時相位也因延遲而使FT 表現量降低。另一方面，自主性開花途徑抑制開花之FLC表現則受抑制，其下游的SOC1表現增加。本研究顯示缺少BPC1、BPC2、BPC4和BPC6，使得BPC3不受拮抗的情況下，兩個主要開花調控的機制同時失去正常調控，顯見BPC轉錄因子以多重調控途徑控制植物生長與發育。本論文亦試圖了解BPC3表現的調控機制，透過酵母菌單雜交篩選，我們找到可能會與BPC3的啟動子有交互作用轉錄因子，目前正嘗試以不同實驗方法驗證轉錄因子的篩選結果。

Plant internal ‘circadian clock’ receives the external fluctuations such as light and temperature to be coordinated with the rhythms of day and night. The circadian clock therefore would keep plants on a track leading to suitable propagation even their rhythms had been randomly interfered. The members of BASIC PENTACYSTEINE (BPC) family are plant-specific transcription factors required for multiple pathways in growth and development. Previous studies have shown that BPC members function overlapping and antagonistically as BPC1, BPC2, BPC4 and BPC6 redundantly antagonize BPC3 during the vegetative growth. By profiling the expression of genes involved in different physiological pathways in the quadruple mutant bpc1-1 bpc2 bpc4 bpc6 (bpc1246), we found that the BPC3 transcript level was over accumulated. In addition, core genes of the circadian clock including CCA1, PRR9, PRR7, PRR5, PRR3, ELF4 and TOC1 were phase-delayed. Consequently, the downstream CO in photoperiodic pathway was also delayed and led a decrease of FT level. We also examined the expression level of FLC, main repressor of flowering in the autonomous pathway. FLC is significantly decreased in bpc1246, and the downstream target SOC1 is increased. Our results revealed that the insufficient antagonization of BPC3 transcription in bpc1246 have simultaneously impeded photoperiodic and autonomous pathways for flowering time control. This indicated that BPC family regulates plant growth and development via multiple pathways. The regulation of BPC3 expression is also preliminarily studied by conducting yeast one-hybrid for finding regulators of the BPC3 promoter. We are currently validating the potential transcription factors for BPC3 expression via various approaches.