百合NCED3基因的差異性表現對離層酸所調控的異形簇生葉生長之影響

Abstract

雖然先前研究報告已指出，外源性離層酸 (abscisic acid, ABA)可調控許多植物的異形葉性；然而，內源性ABA如何調控植物的異形葉性及其分子機制，仍有待進一步釐清。因此，本研究主要以鐵炮型台灣百合 (Lilium formosanum)及東方型香水百合 (Lilium oriental hybrid 'Casa Blanca')兩種不同群種百合為試驗材料，調查ABA對其異形葉型轉換上的影響。結果顯示，簇生苗期呈現鱗片葉生長模式 (scale-leaf-type growth)的鐵炮型台灣百合，其9-cis-epoxycarotenoid dioxygenase 3 (LfNCED3)的轉錄表現較低，且內源性ABA含量較少；而簇生苗期呈現鱗片生長模式 (scale-type growth)的東方型香水百合，則有較高的LoNCED3轉錄表現，並含有較多的內源性ABA含量。高蔗糖逆境誘導內源性ABA生合成的增加，可促使簇生苗期的百合，由鱗片葉生長模式轉變為鱗片生長模式。異質表現LfNCED3或LoNCED3基因於阿拉伯芥Atnced3突變株，皆可矯正其缺陷性狀。有趣的是，LfNCED3及LoNCED3的阿拉伯芥轉殖株，卻呈現出差異性表現。進一步的啟動子序列及活性分析顯示，相較於LoNCED3啟動子，LfNCED3啟動子具有一E2F-like element，且在LfNCED3的基因表現上，扮演著負向調控的角色。因此，本研究顯示，百合群種間，NCED3基因的差異性表現，在異形簇生葉生長模式的調控上，扮演關鍵性的角色。

Although exogenous ABA-regulated heterophylly has been well documented in multiple plant species, the effect of endogenous ABA and its molecular mechanism remain uncharacterized. In the present study, the effects of endogenous ABA on heterophyllous switching were investigated in two different lily varieties, Lilium formosanum and Lilium oriental hybrid ‘Casa Blanca’. Seedlings of L. formosanum, which have scale-leaf-type growth, displayed low levels of both 9-cis-epoxycarotenoid dioxygenase 3 (LfNCED3) transcripts and ABA, whereas seedlings of L. oriental hybrid ‘Casa Blanca’, which have scale-type growth, displayed high levels of both LoNCED3 transcripts and ABA. Sucrose induced endogenous ABA production in cultured lilies; low ABA induction shows scale-leaf-type growth, whereas scale-type growth becomes predominant when ABA levels are high. Heterologous expression of either LfNCED3 or LoNCED3 was found to complement the Arabidopsis Atnced3 mutant. Interestingly, the expression patterns of LfNCED3 and LoNCED3 in transgenic Arabidopsis plants are distinguishable. Further promoter analysis revealed that a putative E2F-like element in the LfNCED3 promoter, but not in the LoNCED3 promoter, plays a negative role in controlling its activity. Collectively, our results demonstrate that NCED3 plays a key role in ABA-mediated heterophylly in lilies.