于和平　侯和勝

摘要：主要闡述了WRKY轉錄因子在非生物脅迫應答中的作用，以及其參與ABA信號轉導方向的研究進展。

關鍵詞：WRKY轉錄因子；非生物脅迫；ABA信號轉導

中圖分類號： S188 文獻標識碼：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，這些脅迫經常發(fā)生在植物生長發(fā)育的不同階段，進而限制了植物的器官生長、組織發(fā)生和果實成熟等。為了適應多變的環(huán)境條件，植物自身存在著復雜的脅迫應答機制，從而實現在不同生長環(huán)境條件下正常生長發(fā)育。基于分子水平的脅迫應答信號轉導在這一過程中起到了至關重要的作用，因此，闡明脅迫響應信號轉導分子機制、識別相關調控因子是研究植物抗逆的關鍵。WRKY轉錄因子作為一種多效性、瞬時性轉錄因子，能夠參與多種生物或非生物脅迫反應以及植物發(fā)育等生理過程[1-2]，但其在脫落酸（ABA）響應的逆境脅迫信號轉導中的作用研究較少。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導機制中扮演重要角色[3]。筆者主要從WRKY轉錄因子在非生物脅迫響應過程中的作用及其參與的ABA信號轉導方面闡述最近的研究進展。

1植物WRKY轉錄因子

2WRKY轉錄因子參與的ABA信號轉導

2.1 ABAR受體介導的ABA信號轉導

ABAR普遍存在于植物的綠色和非綠色組織，在植物細胞中發(fā)揮多重功能，不僅參與葉綠素合成，也是質體與細胞核之間信號轉導的重要組分。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，能夠特異性結合ABA，參與ABA信號轉導，并正向調控信號轉導的發(fā)生[22]。通過免疫熒光技術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末端在基質一側，C末端能夠結合ABA或與一組擬南芥WRKY轉錄因子（AtWRKY18、AtWRKY40、AtWRKY60）相互作用[6, 26]。其中ABAR與AtWRKY40的相互作用表明，AtWRKY40作為主要的負調控因子，可抑制ABA響應基因如ABI5的表達。當外源ABA刺激擬南芥植株時，ABA誘導AtWRKY40從細胞核向細胞質移動，促進ABAR與AtWRKY40的相互作用，從而緩解ABA響應基因的表達抑制。除了AtWRKY18、AtWRKY40、AtWRKY60基因的突變體植株，在ABA誘導的情況下，全部表現ABA過敏感型。除ABAR外，利用ChIP技術發(fā)現，WRKY40還能夠直接與許多ABA響應基因如ABI4、ABI5、ABF4、MYB2等的啟動子結合，從而調控基因表達[6]。這些試驗結果也將WRKY確定在其他已知ABA響應轉錄因子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試驗結果，在種子發(fā)芽及發(fā)育階段，AtWRKY40負調控ABA響應，AtWRKY18和AtWRKY60正調控ABA響應，且AtWRKY18和AtWRKY40能夠被ABA快速誘導，AtWRKY60則較慢。研究人員還發(fā)現，AtWRKY40和AtWRKY18能夠識別AtWRKY60啟動子，調節(jié)AtWRKY60表達，這也說明了WRKY轉錄因子參與ABA信號轉導的復雜性[8]。

2.2PYR/PYL/RCAR受體介導的ABA信號轉導

3展望

隨著新興技術的發(fā)展，植物逆境脅迫響應信號轉導與基因調控領域的研究不斷深入，一些信號受體及轉錄調控因子的識別與定位，為我們更好地理解植物復雜的信號轉導機制提供了新的思路。WRKY轉錄因子作為ABA信號通路中的關鍵調控因子，其參與植物非生物脅迫響應的研究成果，將會在農業(yè)生產上發(fā)揮重要的作用。

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