3-氨基異丁酸對阿拉伯芥的根發育之影響

Abstract

植物演化出許多防禦機制來順應環境上會遭遇的困境，例如面對病菌第一時間會先有一個快速的免疫機制來保護植物。本篇論文研究一種人工合成胺基酸β-aminobutyric acid (BABA)，可藉由priming的機制來對抗生物或非生物性的入侵，例如生物性抵抗病菌的入侵、非生物性的抗乾旱以及抗鹽等。本文以BABA對植物的根所造成的影響為主要研究對象，因為根系統(root system)無論在適應逆境、支撐架構、和吸收養分都扮演很重要的角色。我們發現，當阿拉伯芥吸收到BABA，主根會被抑制、側根密度會增多、並且根毛也是會變多和變長的情況，這些現象，似乎跟植物的賀爾蒙，生長素和乙烯有關。我們認為，BABA可藉由調控這兩個賀爾蒙來影響根的生長，使側根和根毛因此增多，同時我們也發現兩個生長素變種株對BABA的敏感度也異於平常，之後我們會更進一步的研究與分析此一現象。 此外，我們發現BABA對根生長的方向也有影響。之前的研究指出，重力、水分與營養、向性、光、環境障礙等都會影響根生長的方向。我們發現BABA似乎與propyzamide有同樣的功能，都可以改變根的細胞骨架中的微管，進而改變根生長的方向。此外，我們也發現，ibuprofen，一種茉莉酮酸酯(jasmonate)抑制劑，似乎也是跟BABA藉由相同的方式改變根的生長方向，因此當根吸收到BABA和ibuprofen，在交互作用下而減少了BABA對根的抑制。

Plants have developed numerous, complex defense mechanisms to escape infection by pathogens. The non-protein amino acid β-aminobutyric acid (BABA) is known as a plant resistance inducer against abiotic and biotic stresses. Its enhanced plant capacity to mobilize defense responses, this phenomenon is called “priming”. Priming has been notably studied in Arabidopsis thaliana against drought and salt stresses and various pathogens. However, little is known about the effects of BABA on plant development. To clarify this, we analyzed the mode of action of BABA on root development and observed that BABA inhibits primary root growth and increases lateral root density. Roots of higher plants, to adapt to their environment and gain maximum advantage for growth, change their growth direction in response to various environmental stimuli, such as gravity, light, moisture, nutrients, temperature and obstacles. To study BABA effects on root adaptation to their environment, we analyzed how BABA changes root response to environmental stimuli. BABA was found to alter the direction of root growth. In addition, this work shows for the first time that ibuprofen, a jasmonic acid inhibitor, also alters root growth direction. Auxin and ethylene play an important role in primary root development; lateral root formation and root hair elongation. Our results suggest that BABA regulates root hairs development, but not lateral roots formation, through interactions with auxin and ethylene. Taken together, our data show that BABA does not only increase plant resistance to stress, but also affect plant development and plasticity.