植物WRKY轉(zhuǎn)錄因子及其參與的ABA信號轉(zhuǎn)導(dǎo)

于和平　侯和勝

摘要：主要闡述了WRKY轉(zhuǎn)錄因子在非生物脅迫應(yīng)答中的作用，以及其參與ABA信號轉(zhuǎn)導(dǎo)方向的研究進(jìn)展。

關(guān)鍵詞：WRKY轉(zhuǎn)錄因子；非生物脅迫；ABA信號轉(zhuǎn)導(dǎo)

中圖分類號： S188 文獻(xiàn)標(biāo)識碼：DOI編碼：10.3969/j.issn.1006－6500.2012.06.005

由于植物的固著屬性及自然界的環(huán)境變化，農(nóng)林作物等植物時刻遭受著各種生物和非生物的脅迫，如病蟲害、干旱、低溫、高鹽等，這些脅迫經(jīng)常發(fā)生在植物生長發(fā)育的不同階段，進(jìn)而限制了植物的器官生長、組織發(fā)生和果實成熟等。為了適應(yīng)多變的環(huán)境條件，植物自身存在著復(fù)雜的脅迫應(yīng)答機制，從而實現(xiàn)在不同生長環(huán)境條件下正常生長發(fā)育。基于分子水平的脅迫應(yīng)答信號轉(zhuǎn)導(dǎo)在這一過程中起到了至關(guān)重要的作用，因此，闡明脅迫響應(yīng)信號轉(zhuǎn)導(dǎo)分子機制、識別相關(guān)調(diào)控因子是研究植物抗逆的關(guān)鍵。WRKY轉(zhuǎn)錄因子作為一種多效性、瞬時性轉(zhuǎn)錄因子，能夠參與多種生物或非生物脅迫反應(yīng)以及植物發(fā)育等生理過程[1-2]，但其在脫落酸（ABA）響應(yīng)的逆境脅迫信號轉(zhuǎn)導(dǎo)中的作用研究較少。研究表明，ABA作為傳統(tǒng)的植物激素之一，在植物逆境脅迫信號轉(zhuǎn)導(dǎo)機制中扮演重要角色[3]。筆者主要從WRKY轉(zhuǎn)錄因子在非生物脅迫響應(yīng)過程中的作用及其參與的ABA信號轉(zhuǎn)導(dǎo)方面闡述最近的研究進(jìn)展。

1植物WRKY轉(zhuǎn)錄因子

2WRKY轉(zhuǎn)錄因子參與的ABA信號轉(zhuǎn)導(dǎo)

2.1 ABAR受體介導(dǎo)的ABA信號轉(zhuǎn)導(dǎo)

ABAR普遍存在于植物的綠色和非綠色組織，在植物細(xì)胞中發(fā)揮多重功能，不僅參與葉綠素合成，也是質(zhì)體與細(xì)胞核之間信號轉(zhuǎn)導(dǎo)的重要組分。研究表明，在種子發(fā)芽、生長和氣孔運動過程中ABAR作為受體，能夠特異性結(jié)合ABA，參與ABA信號轉(zhuǎn)導(dǎo)，并正向調(diào)控信號轉(zhuǎn)導(dǎo)的發(fā)生[22]。通過免疫熒光技術(shù)和酵母雙雜交篩選證明，ABAR定位于葉綠體膜邊緣，能夠橫跨葉綠體膜，并且其N末端和C末端在基質(zhì)一側(cè)，C末端能夠結(jié)合ABA或與一組擬南芥WRKY轉(zhuǎn)錄因子（AtWRKY18、AtWRKY40、AtWRKY60）相互作用[6, 26]。其中ABAR與AtWRKY40的相互作用表明，AtWRKY40作為主要的負(fù)調(diào)控因子，可抑制ABA響應(yīng)基因如ABI5的表達(dá)。當(dāng)外源ABA刺激擬南芥植株時，ABA誘導(dǎo)AtWRKY40從細(xì)胞核向細(xì)胞質(zhì)移動，促進(jìn)ABAR與AtWRKY40的相互作用，從而緩解ABA響應(yīng)基因的表達(dá)抑制。除了AtWRKY18、AtWRKY40、AtWRKY60基因的突變體植株，在ABA誘導(dǎo)的情況下，全部表現(xiàn)ABA過敏感型。除ABAR外，利用ChIP技術(shù)發(fā)現(xiàn)，WRKY40還能夠直接與許多ABA響應(yīng)基因如ABI4、ABI5、ABF4、MYB2等的啟動子結(jié)合，從而調(diào)控基因表達(dá)[6]。這些試驗結(jié)果也將WRKY確定在其他已知ABA響應(yīng)轉(zhuǎn)錄因子AP2/ERF基因DREB1A、MYB基因MYB2、bZIP基因ABI5等的上游。分析單雙突變和過表達(dá)試驗結(jié)果，在種子發(fā)芽及發(fā)育階段，AtWRKY40負(fù)調(diào)控ABA響應(yīng)，AtWRKY18和AtWRKY60正調(diào)控ABA響應(yīng)，且AtWRKY18和AtWRKY40能夠被ABA快速誘導(dǎo)，AtWRKY60則較慢。研究人員還發(fā)現(xiàn)，AtWRKY40和AtWRKY18能夠識別AtWRKY60啟動子，調(diào)節(jié)AtWRKY60表達(dá)，這也說明了WRKY轉(zhuǎn)錄因子參與ABA信號轉(zhuǎn)導(dǎo)的復(fù)雜性[8]。

2.2PYR/PYL/RCAR受體介導(dǎo)的ABA信號轉(zhuǎn)導(dǎo)

3展望

隨著新興技術(shù)的發(fā)展，植物逆境脅迫響應(yīng)信號轉(zhuǎn)導(dǎo)與基因調(diào)控領(lǐng)域的研究不斷深入，一些信號受體及轉(zhuǎn)錄調(diào)控因子的識別與定位，為我們更好地理解植物復(fù)雜的信號轉(zhuǎn)導(dǎo)機制提供了新的思路。WRKY轉(zhuǎn)錄因子作為ABA信號通路中的關(guān)鍵調(diào)控因子，其參與植物非生物脅迫響應(yīng)的研究成果，將會在農(nóng)業(yè)生產(chǎn)上發(fā)揮重要的作用。

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