離層酸可參與生長素生合成之改變及分布來促進水稻幼苗根尖膨大

Abscisic Acid Promotes Root-tip Swelling is Involved in Alteration of Auxin Biosynthesis and Distribution in Rice Seedlings

郭哲瑋(Che-Wei Kuo)

指導教授 ： 張孟基

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201603576

摘要

根是植物重要的器官，可以吸收土壤中的水及養分、固定植物及儲存能量。而根形態構造的形成與植物生長發育及環境適應性密切相關，其中植物荷爾蒙扮演重要之角色。先前研究發現，外源施加的離層酸 (Abscisic acid, ABA) 可以促進台中在來一號 (TCN1) 幼苗的根尖膨大 (Root tip swelling) ，但其相關機制並不清楚。目前諸多研究指出植物荷爾蒙生長素 (Auxin) 與根生長發育密切相關，影響側根原基形成及根毛生長。因此本試驗目的為瞭解ABA在促進根尖膨大的過程中，生長素是否參與其中。本試驗首先以不同的水稻品種為實驗材料，發現不論稉、秈稻，外加ABA皆可以誘導根尖膨大。利用生長素誘導報導基因 (DR5::GUS) 之水稻轉殖株以ABA處理發現，生長素的分布會隨著根尖膨大程度而逐漸聚集於根尖區域，且在處理15小時後最為明顯。在根尖膨大的區域也偵測到生長素 (IAA) 含量的上升。此外，處理生長素生合成的抑制劑 (Kynurenine, Yucasin) 及極性運輸抑制劑 (NPA) 可以有效地抑制離層酸所誘導的根尖膨大現象。而外源施加IAA則可以使被抑制的膨大現象恢復。在ABA處理之下，根尖區域的生長素相關基因 (OsIAAs, OsPINs, OsYUCs) 及細胞壁合成相關基因 (OsEXPs) 都有表現量上升的情形。以上結果顯示，外源施加ABA所誘導的水稻根尖膨大是透過改變生長素之生合成及分布所達成的。

關鍵字

離層酸 ； 生長素 ； 抑制劑 ； 根尖膨大

並列摘要

Root is an important organ, which provides several functions for plant growth including resource uptake from soil, anchorage, nutrient transport, and energy storage. Phytohormones are known to play vital roles in these processes. Our previous study has indicated that exogenously added ABA can induce root tip swelling in indica rice (TCN1). Since auxin can regulate many aspects of root development, including lateral root primordium formation and root hair elongation, in this study we investigated whether auxin plays a role in the ABA-mediated root tip swelling in rice. The results showed that ABA-mediated root tip swelling exists in both japonica and indica rice. Histochemical staining of GUS activity driven by an auxin-responsive synthetic promoter (DR5) shown that ABA-mediated root tip swelling was accompanied with a redistribution of auxin. The indole acetic acid (IAA) level was also increased in root tip region. Moreover, the effects of ABA on root tip swelling was repressed by Kynurenine (Kyn) or Yucasin, two auxin biosynthetic inhibitors and NPA, an auxin transporter inhibitor. However, the effects of inhibitors on ABA-mediated root tip swelling can be rescued by exogenous IAA. Meanwhile, auxin related and cell wall related genes were upregulated in root tip with ABA treatment. Taken together, these data suggest that ABA-mediated root tip swelling is dependent on the change of auxin biosynthesis and distribution.

並列關鍵字

ABA ； auxin ； inhibitors ； root tip swelling

參考文獻

Abu-Zaitoon, Y. M., Bennett, K., Normanly, J. & Nonhebel, H. M. (2012). A large increase in IAA during development of rice grains correlates with the expression of tryptophan aminotransferase OsTAR1 and a grain-specific YUCCA. Physiologia Plantarum 146(4): 487-499.

Ariel, F., Diet, A., Verdenaud, M., Gruber, V., Frugier, F., Chan, R. & Crespi, M. (2010). Environmental regulation of lateral root emergence in medicago truncatula requires the HD-Zip I transcription factor HB1. The Plant Cell 22(7): 2171-2183.

Baskin, T. I., Beemster, G. T. S., Judy-March, J. E. & Marga, F. (2004). Disorganization of cortical microtubules stimulates tangential expansion and reduces the uniformity of cellulose microfibril alignment among cells in the root of Arabidopsis. Plant Physiology 135(4): 2279-2290.

Chen, C.-W. (2003).ABscisic Acid Induces Morphological and Physiological Changes in Roots of Rce (Oryza sativa L.) seedlings of cultivar Taichung Native 1. In Master thesis. National Taiwan University.

Chen, C.-W., Yang, Y.-W., Lur, H.-S., Tsai, Y.-G. & Chang, M.-C. (2006). A novel function of abscisic acid in the regulation of rice (Oryza sativa L.) root growth and development. Plant and Cell Physiology 47(1): 1-13.