- 學位論文
阿拉伯芥的ERF1在遭受到非生物逆境時會結合到不同的cis-element上進而調節逆境基因的表現
The Arabidopsis ERF1 regulates abiotic-stress-responsive gene expression by binding to different cis-acting elements under different stress signalings
摘要
Ethylene Response Factor 1 (ERF1) 是一個在茉莉酸(JA)和乙烯(ET)訊息傳遞的上游因子，並參與植株的抗病反應。許多報導顯示ERF1可能透過乙烯的訊息傳遞參與在高鹽逆境反應，但ERF1在非生物性逆境上的明確角色以及交叉訊息傳遞下的分子機制仍未明瞭。本篇研究發現，ERF1可被乾旱以及高鹽逆境大量誘導表現，而且其鹽誘導需要茉莉酸以及乙烯訊息同時作用，然而會被離層酸(ABA)所抑制。在乾旱以及高鹽逆境下，ERF1的大量表現轉植株都較野生型有較高的存活率，同時，其氣孔張開程度較小且水分散失速率較低。令人意外的是，ERF1的大量表現轉植株相較於野生型也有較高的熱耐受性且其耐熱基因有高度表現的現象。透過微陣列分析，我們挑選出在ERF1大量表現轉植株中高度表現的數組和茉莉酸、乾旱、高鹽以及耐熱相關的基因。利用染色體免疫沉澱法分析，我們發現ERF1蛋白在不同的非生物性逆境下可以透過專一性的結合到GCC或是DRE/CRT來調控特定幾組基因。在生物性逆境下，ERF1蛋白會結合到GCC box而非DRE element，相反地，在非生物性逆境下，ERF1蛋白會結合到DRE element。我們也發現，在目標基因啟動子序列上的許多GCC box或DRE element中，ERF1傾向於只結合到一個GCC box或DRE element。綜合以上，ERF1透過逆境專一性的基因調控，在高鹽、乾旱以及熱逆境上扮演正向的角色，且在茉莉酸、乙烯以及離層酸的訊息傳遞中有著交會點的功能。
並列摘要
Ethylene Response Factor 1 (ERF1) is an upstream component in both jasmonate (JA) and ethylene (ET) signaling, and is involved in pathogen resistance. Accumulating evidence suggests that ERF1 might be related to salt stress response through ethylene signaling. However, the specific role of ERF1 in abiotic stress and the molecular mechanism underlying the signaling crosstalk still need to be elucidated. Here, I report that ERF1 was highly induced by high salinity and drought stress. The salt-stress induction required both JA and ET signaling but was inhibited by abscisic acid (ABA). ERF1 overexpressing lines (35S:ERF1) were more tolerant to drought and salt stress. They also displayed constitutively smaller stomatal aperture, less transpirational water loss. Surprisingly, 35S:ERF1 also showed enhanced heat tolerance and upregulation of heat tolerance genes compared with WT. Several suites of genes activated by JA, drought, salt, and heat were found in microarray analysis of 35S:ERF1. Chromatin immunoprecipitation assays found that ERF1 upregulates specific suites of genes in response to different abiotic stresses by stress-specific binding to GCC or DRE/CRT. In response to biotic stress, ERF1 bound to GCC boxes but not DRE elements and conversely, under abiotic stress we observed specific binding of ERF1 to DRE elements. Furthermore, ERF1 bound preferentially to only one among several GCC box or DRE/CRT elements in the promoter region of its target genes. ERF1 plays a positive role in salt, drought, and heat stress tolerance by stress specific gene regulation which integrates JA, ET and ABA signals.