- 學位論文
文心蘭miR156-SPL (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE) 調控模組於高溫誘導開花機制之功能性探討
Functional study of miR156-SPL (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE) regulatory module involved in high temperature-induced flowering mechanism in Oncidium Gower Ramsey
摘要
前人研究指出高溫透過細胞質抗壞血酸過氧化酶 (Oncidium cytosolic ascorbate peroxidase 1，OgcytAPX1) 影響維他命C (ascorbate) 氧化還原比例 (還原/氧化)，進而誘導文心蘭萳西品系 (Oncidium Gower Ramsey) 開花。此外，在阿拉伯芥中大量表現OgcytAPX1，經過熱處理後能夠誘導miR156的目標基因SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3 (SPL3) 表現。目前已知miR156-SPL調控模組參與阿拉伯芥花期調控，但尚不明瞭其詳細調控機制。為了解文心蘭中是否存在miR156-SPL調控模組與其位於高溫誘導開花機制中的調控角色，本研究在文心蘭中找到三條受miR156所調控的SPL基因 (OgSPLs)，並且分析比較不同生長階段文心蘭假球莖中miR156-SPL調控模組的表現。結果顯示隨著植株生育年齡增長，miR156會逐漸下降；反之OgSPLs則逐漸上升。高溫處理能誘導假球莖與花芽中的OgSPLs表現，外加維他命C則能抑制此誘導效益。然而，不論高溫處理或外加維他命C，都不會顯著影響miR156的表現。結果說明，高溫不需透過miR156，即可直接影響OgSPLs之基因表現。此外，在阿拉伯芥cytAPX1基因缺失突變株apx1中大量表現OgSPLs，可恢復apx1較野生型晚開花的表現型，顯示OgSPLs的調控開花功能作用於OgcytAPX1之下游。綜合上述結果可推論，OgSPLs在文心蘭自然發育過程中受miR156調控植物生長週期；然而，在文心蘭植株進入成熟期後，高溫藉由維他命C氧化還原比例所誘導的開花過程，則不需經由miR156即能直接促進OgSPLs表現而提早開花。
並列摘要
Previous studies have shown that high temperature-induced flowering is regulated by Oncidium cytosolic ascorbate peroxidase 1 (OgcytAPX1) through mediating the redox state of ascorbate (AsA) in Oncidium Gower Ramsey. Ecotopically overexpressing OgcytAPX1 in Arabidopsis can induce the expression of miRNA156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3 (SPL3) under high-temperature treatment. The miR156-SPL regulatory module has been known to regulate flowering in Arabidopsis, but its specific regulatory role on flowering is unclear. In order to dissect the function of miR156-SPL regulatory module on high temperature-induced flowering in Oncidium. We found three possible miR156-target SPL genes in Oncidium (OgSPLs). The study on expression profiling of Oncidium pseudobulbs at different growth stages indicated that miR156 steadily decreased, and OgSPLs increased as the Oncidium matures. Higher growth temperature increased OgSPLs transcription levels in both pseudobulbs and inflorescence buds, but the effect diminished after AsA application. However, the influence on miR156 under these treatments was not significant, suggesting that OgSPLs was independent of miR156 in high temperature-induced flowering mechanism. Meanwhile, ecotopically overexpressing OgSPLs in Arabidopsis mutant apx1 restored the delayed flowering phenotype compared to WT, suggesting that flowering regulation of OgSPLs was located at the downstream of OgcytAPX1. In conclusion, these results indicate that miR156 regulates phase transition through OgSPLs; however, OgSPLs act independently of age-mediated miR156 as one of the AsA redox downstream signal on the high temperature-induced flowering processes in the adult Oncidium.