植物激素脫落酸（ABA）調(diào)節(jié)植物生長(zhǎng)發(fā)育過程和植物對(duì)逆境的適應(yīng),。ABA信號(hào)首先通過細(xì)胞受體被識(shí)別，然后引起一系列細(xì)胞內(nèi)下游信號(hào)轉(zhuǎn)導(dǎo)事件,，最終導(dǎo)致生物學(xué)效應(yīng)。研究證明,，ABA信號(hào)受體有多種,，包括細(xì)胞表面受體和細(xì)胞內(nèi)受體。張大鵬研究組以前鑒定了一種細(xì)胞內(nèi)葉綠體中的ABA受體,，命名為ABAR（Nature, 2006, 443: 823-826）,。之后他們提供了ABAR是ABA受體的進(jìn)一步的生物化學(xué)和遺傳學(xué)證據(jù)；而且,，發(fā)現(xiàn)ABAR分子的C-端是結(jié)合ABA和介導(dǎo)ABA信號(hào)的核心區(qū)（Plant Physiology, 2009, 150: 1940-1954）,。但是，ABAR介導(dǎo)的下游信號(hào)通路一直是懸而未決的問題,。
生物谷啟用新域名 www.bioon.net
張大鵬研究組發(fā)現(xiàn),，ABAR是一個(gè)跨越葉綠體被膜的蛋白質(zhì)，其C-端和N-端曝露在細(xì)胞質(zhì)中,；ABAR在細(xì)胞質(zhì)一側(cè)的C-端部分與一組WRKY轉(zhuǎn)錄因子（AD1A/WRKY40,、AD1B/WRKY18、AD1C/WRKY60）互相作用,。他們提供的遺傳學(xué)和生物化學(xué)證據(jù)表明,，AD1A/B/C是一組轉(zhuǎn)錄抑制因子，負(fù)調(diào)節(jié)ABA信號(hào)通路；AD1A是其中的核心調(diào)節(jié)子,。ABAR與ABA信號(hào)分子結(jié)合后,，可以刺激AD1A從細(xì)胞核到細(xì)胞質(zhì)的轉(zhuǎn)移，促進(jìn)ABAR與AD1A的互相作用,；進(jìn)而激發(fā)一種未知因子（或信號(hào)系統(tǒng)）,，阻遏AD1A的表達(dá)，從而解除AD1A對(duì)ABA響應(yīng)基因（比如ABI5等）轉(zhuǎn)錄的抑制,，最終實(shí)現(xiàn)ABA的生理效應(yīng),。
這些發(fā)現(xiàn)描述了一個(gè)從信號(hào)原初識(shí)別到下游基因表達(dá)的新的ABA信號(hào)通路（即ABA-ABAR-AD1A-ABI5信號(hào)級(jí)聯(lián)通路，參見圖1）,。研究論文于6月11日在線發(fā)表于國際著名植物學(xué)期刊Plant Cell,。(生物谷Bioon.net)
生物谷推薦原文出處：
Plant Cell doi:10.1105/tpc.110.073874
The Mg-Chelatase H Subunit of Arabidopsis Antagonizes a Group of Transcription Repressors to Relieve ABA-Responsive Genes of Inhibition
Yi Shanga,1, Lu Yana,b,1, Zhi-Qiang Liua,b,1, Zheng Caoa,b,1, Chao Meia,1, Qi Xina,b, Fu-Qing Wua,b, Xiao-Fang Wanga,b, Shu-Yuan Dua, Tao Jianga,b, Xiao-Feng Zhanga, Rui Zhaoa,b, Hai-Li Suna,b, Rui Liua,b, Yong-Tao Yua and Da-Peng Zhanga,2
a Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
b College of Biological Sciences, China Agricultural University, Beijing 100094, China
The phytohormone abscisic acid (ABA) plays a vital role in plant development and response to environmental challenges, but the complex networks of ABA signaling pathways are poorly understood. We previously reported that a chloroplast protein, the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR), functions as a receptor for ABA in Arabidopsis thaliana. Here, we report that ABAR spans the chloroplast envelope and that the cytosolic C terminus of ABAR interacts with a group of WRKY transcription factors (AD1A/WRKY40, AD1B/WRKY18, and AD1C/WRKY60) that function as negative regulators of ABA signaling in seed germination and postgermination growth. AD1A, a central negative regulator, inhibits expression of ABA-responsive genes, such as ABI5. In response to a high level of ABA signal that recruits AD1A from the nucleus to the cytosol and promotes ABAR–AD1A interaction, ABAR relieves the ABI5 gene of inhibition by repressing AD1A expression. These findings describe a unique ABA signaling pathway from the early signaling events to downstream gene expression.
