孫曉琛，栗錦鵬，原靜靜，王惠珍，杜弢

WRKY轉(zhuǎn)錄因子在植物干旱響應(yīng)機(jī)制中的作用研究進(jìn)展

孫曉琛，栗錦鵬，原靜靜，王惠珍，杜弢

甘肅中醫(yī)藥大學(xué)藥學(xué)院，甘肅 蘭州 730000

WRKY轉(zhuǎn)錄因子是調(diào)控植物發(fā)育和應(yīng)對(duì)外界脅迫刺激反應(yīng)的主要調(diào)控因子，在植物抵御干旱過程中的作用至關(guān)重要。本文就近年來WRKY轉(zhuǎn)錄因子抵御干旱脅迫依賴的信號(hào)通路、干旱脅迫下其參與的植物生長(zhǎng)發(fā)育和生理調(diào)控，以及對(duì)藥用植物次生代謝產(chǎn)物的調(diào)控相關(guān)研究進(jìn)行梳理，為進(jìn)一步探討植物的抗旱分子機(jī)制、培育耐旱品系，探索植物次生代謝產(chǎn)物的藥用價(jià)值提供參考。

WRKY轉(zhuǎn)錄因子；干旱脅迫；信號(hào)通路；生長(zhǎng)發(fā)育；次級(jí)代謝產(chǎn)物；綜述

植物早期從水生環(huán)境遷移到陸地易遭受干旱脅迫、鹽害、極端溫度等不利因素影響，其中干旱脅迫會(huì)對(duì)植物造成致命傷害[1]，因此，提高植物對(duì)干旱脅迫的耐受性是迄今植物保護(hù)地區(qū)促進(jìn)可持續(xù)發(fā)展的有效策略，越來越多的國(guó)家和國(guó)際組織也在積極開展探索植物抗旱機(jī)制的相關(guān)研究，以確定提高植物抗旱性的關(guān)鍵基因或工具。在分子水平上，脅迫相關(guān)基因的誘導(dǎo)有助于提高植物適應(yīng)不利環(huán)境因子的能力，在該過程中，許多轉(zhuǎn)錄調(diào)控網(wǎng)絡(luò)被激活，其中WRKY作為植物中最大的轉(zhuǎn)錄因子家族之一，在植物對(duì)干旱脅迫反應(yīng)的調(diào)控網(wǎng)絡(luò)中發(fā)揮重要作用[2]。

最初，WRKY被認(rèn)為是高等植物特有的，后在蕨類植物和藍(lán)氏賈第鞭毛蟲與盤狀網(wǎng)柄菌中鑒定出WRKY基因[3]，表明其為起源于原核生物與真核生物分化之前的轉(zhuǎn)錄因子大家族。首個(gè)WRKY cDNASPF1是從甘薯[4]中克隆所得，隨后ABF1,2在野燕麥[5]中發(fā)現(xiàn)并進(jìn)一步在皺葉歐芹中得到WRKY1、WRKY2和WRKY3，并創(chuàng)造WRKY[6]。WRKY家族成員共同特征是具有高度保守的60個(gè)氨基酸區(qū)域的結(jié)構(gòu)域，由N末端保守氨基酸序列WRKY GQK和C末端鋅指狀基序C2H2或C2HC組成[7]。該結(jié)構(gòu)域可形成一種4條鏈的β-折疊，其穩(wěn)定性由β-折疊端的鋅結(jié)合袋所決定，表明N端保守序列可以直接與DNA結(jié)合[8]。根據(jù)WRKY結(jié)構(gòu)域的數(shù)量和鋅指狀基序的類型，通常將其分為以下3組亞家族，由此反映其不同功能：第一組由2個(gè)WRKY結(jié)構(gòu)域組成，分為Ia和Ib亞組，Ia含C2HC鋅指，Ib也含有C2HC鋅指；第二組只有1個(gè)WRKY結(jié)構(gòu)域和1個(gè)C2H2鋅指，根據(jù)其系統(tǒng)發(fā)育關(guān)系分為5個(gè)亞組，即Ia、Ib、Ic、Id和Ie；第三組也只有1個(gè)WRKY結(jié)構(gòu)域，但其鋅指結(jié)構(gòu)為C2HC[7]。多數(shù)WRKY轉(zhuǎn)錄因子可通過核定位信號(hào)、亮氨酸拉鏈、絲氨酸/蘇氨酸富集區(qū)、富含谷氨酰胺的區(qū)域、富含脯氨酸的區(qū)域、激酶結(jié)構(gòu)域、TIR-NBS-LRr等結(jié)構(gòu)參與植物的多種調(diào)節(jié)途徑[2]。近10年來，WRKY不僅在農(nóng)作物和果蔬煙草抵御干旱脅迫機(jī)制中研究廣泛，還在人參、丹參、紅豆杉、青蒿等植物次級(jí)代謝產(chǎn)物的藥用價(jià)值中取得進(jìn)展。茲就相關(guān)研究進(jìn)行綜述。

1 WRKY調(diào)控植物抗旱反應(yīng)

WRKY是最大的植物特異性轉(zhuǎn)錄因子超家族之一，可通過識(shí)別和結(jié)合其啟動(dòng)子中的W盒（TTGACC/T）正調(diào)控下游基因表達(dá)，而這些下游基因又通過多種生理過程賦予植物非生物脅迫和生物脅迫耐受性，使其成為改善干旱脅迫反應(yīng)中的主要候選靶基因[9]。此外，WRKY家族成員還在調(diào)控植株胚胎、莖葉生長(zhǎng)，衰老、糖信號(hào)傳導(dǎo)及毛狀體形態(tài)中起著重要作用[10]。見表1。

表1 部分響應(yīng)干旱的WRKY轉(zhuǎn)錄因子

基因物種研究方法文獻(xiàn) AtWRKY46，AtWRKY54，AtWRKY70擬南芥Arabidopsis thaliana轉(zhuǎn)錄組分析[11] AtWRKY57擬南芥Arabidopsis thaliana獲得功能突變體[12] MdWRKY20，MdWRKY22，MdWRKY40，MdWRKY47，MdWRKY53，MdWRKY77，MdWRKY90，MdWRKY91，MdWRKY100，MdWRKY125蘋果Malus domestica轉(zhuǎn)錄組分析[13] VlWRKY48，VlWRKY30葡萄Vitis vinifera過表達(dá)到擬南芥[14-15] HvWRKY38大麥Hordeum vulgare轉(zhuǎn)錄組分析[16] TaWRKY1，TaWRKY33小麥Triticum aestivum過表達(dá)到擬南芥[17] OsWRKY30，OsWRKY45水稻Oryza satiwa過表達(dá)到擬南芥[18-19] ZmWRKY58玉米Zea mays過表達(dá)到水稻[20] NtWRKY3，NtWRKY10，NtWRKY12，NtWRKY69煙草Nicotiana tabacum轉(zhuǎn)錄組分析[21] GsWRKY20野大豆Glycine soja過表達(dá)到苜蓿[22] MtWRKY76蒺藜苜蓿Medicago truncatula過表達(dá)[23] CmWRKY10菊花Chrysanthemum過表達(dá)[24] ZbWRKY33花椒Zanthoxylum bungeanum過表達(dá)[25] PtrWRKY2 枳Poncirus trifoliata RNA印跡分析[26] PbWRKY白梨Pyrus bretschneideri 轉(zhuǎn)錄組分析[27] IbWRKY2番薯Ipomoea batatas轉(zhuǎn)錄組分析[28] BcWRKY46不結(jié)球白菜Brassica campestris過表達(dá)到煙草[29] MuWRKY3硬皮豆Macrotyloma uniflorum過表達(dá)到花生[30]

1.1 干旱脅迫下WRKY依賴的信號(hào)通路

干旱應(yīng)激信號(hào)傳導(dǎo)途徑包括信號(hào)感知、信號(hào)傳導(dǎo)、應(yīng)激反應(yīng)。首先，植物細(xì)胞膜上的各種質(zhì)膜蛋白作為傳感器感知脅迫信號(hào)，然后由激素和第二信使活性氧自由基、Ca2+、環(huán)核苷酸（cAMP和cGMP）等啟動(dòng)相應(yīng)的信號(hào)轉(zhuǎn)導(dǎo)途徑，最終影響調(diào)節(jié)網(wǎng)絡(luò)并誘導(dǎo)應(yīng)激反應(yīng)基因的表達(dá)[31]。

1.1.1 自我調(diào)節(jié)和交叉調(diào)節(jié)

轉(zhuǎn)錄因子可通過與相同蛋白質(zhì)或同一家族其他成員的物理相互作用分別形成同二聚體或異二聚體，或與其他蛋白質(zhì)家族的轉(zhuǎn)錄因子建立復(fù)合物，并在轉(zhuǎn)錄調(diào)控過程中提供巨大的組合靈活性[31]。因此，該轉(zhuǎn)錄因子不僅能實(shí)現(xiàn)WRKY-WRKY蛋白作用，如番茄中由干旱誘導(dǎo)的9個(gè)WRKY基因，尤其WRKY58，可單獨(dú)或與其他基因組合進(jìn)一步作為耐旱轉(zhuǎn)基因的靶標(biāo)[32]；還可以與其他蛋白相互作用，如ZmWRKY25、ZmWRKY47、ZmWRKY80的啟動(dòng)子具有W盒順式作用元件，這3種蛋白可相互作用，并通過與其他蛋白質(zhì)相互作用而參與干旱響應(yīng)[2]。

盡管WRKY具有功能多樣性，但幾乎所有WRKY蛋白都能識(shí)別W盒序列，因此，除識(shí)別核心W盒啟動(dòng)子元件外，還需其他機(jī)制以實(shí)現(xiàn)WRKY轉(zhuǎn)錄因子的調(diào)控特異性[33]。如單個(gè)WRKY蛋白可與多個(gè)轉(zhuǎn)錄調(diào)控輔助因子VQ蛋白的相互作用，賦予WRKY蛋白廣泛的生物學(xué)功能，干旱能誘導(dǎo)VQ蛋白表達(dá)，IbWRKY2通過與IbVQ4和AtVQ4交互作用，充當(dāng)植物干旱脅迫耐受性的正調(diào)節(jié)劑[28]。

1.1.2 絲裂原活化蛋白激酶對(duì)WRKY的調(diào)節(jié)

絲裂原活化蛋白激酶（MAPK）級(jí)聯(lián)是植物感受到內(nèi)部發(fā)育和外部生物脅迫和非生物脅迫信號(hào)后被激活的中樞信號(hào)通路，其中已確定MAPK信號(hào)通路參與干旱脅迫響應(yīng)[34]。WRKY可被MAPK磷酸化，與其啟動(dòng)子區(qū)的特定順式元件相互作用直接調(diào)節(jié)一系列下游基因表達(dá)[35]。如煙草中MAP激酶WIPK和苜蓿中SAMK可被寒冷、干旱、傷害和生物信號(hào)激活[36]。Shen等[18]研究表明，MAP激酶激活OsWRKY30的過表達(dá)賦予植株耐旱性，其過程為OsWRKY30與OsMPK3、OsMPK4、OsMPK7、OsMPK14、OsMPK20-4及OsMPK20-5相互作用，同時(shí)被OsMPK3、OsMPK7和OsMPK14磷酸化。Li等[37]鑒定了1個(gè)完整的MAP激酶級(jí)聯(lián)反應(yīng)，在此反應(yīng)中其介導(dǎo)GhWRKY轉(zhuǎn)錄因子被激活并磷酸化，還闡明了一種由GhMAP3K15-GhMKK4-GhMPK6-GhWRKY59- GhDREB2組成調(diào)控模塊，該模塊參與控制棉花的干旱反應(yīng)。

1.2 WRKY參與脫落酸介導(dǎo)的信號(hào)途徑

一般而言，干旱反應(yīng)途徑可分為兩類：一類是脫落酸（ABA）依賴途徑，另一類則獨(dú)立于ABA。一方面，ABA作為一種脅迫信號(hào)在植物的干旱脅迫反應(yīng)中充當(dāng)內(nèi)源信使，還可在脅迫條件下對(duì)植物的生長(zhǎng)發(fā)育進(jìn)行微調(diào)，控制的生理過程包括生長(zhǎng)、氣孔孔徑和導(dǎo)水率的調(diào)節(jié)等[38]。9-順式環(huán)氧類胡蘿卜素雙加氧酶（NCED）是干旱脅迫下ABA合成的關(guān)鍵酶，NCED基因的過度表達(dá)可增強(qiáng)ABA積累，增強(qiáng)植物的抗旱能力，Liu等[39]研究表明，PbrWRKY53是一個(gè)抗旱積極因子，能直接與PbrNCED1啟動(dòng)子結(jié)合并正調(diào)控PbrNCED1表達(dá)響應(yīng)干旱。在小麥研究中檢測(cè)到脫落酸合成基因ABA1和ABA2，意味著ABA生產(chǎn)加速，且ABI5轉(zhuǎn)錄豐度增加，表明TaWRKY33通過脫落酸合成和轉(zhuǎn)導(dǎo)途徑提高耐旱水平[17]。另一方面，ABA可修飾組成性表達(dá)的轉(zhuǎn)錄因子，導(dǎo)致早期反應(yīng)轉(zhuǎn)錄激活因子表達(dá)，然后激活下游脅迫耐受效應(yīng)基因[40]。甘油醛-3-磷酸脫氫酶是一種在非生物脅迫和植物發(fā)育過程中發(fā)揮重要作用的多功能酶。Zhang等[41]研究表明，當(dāng)植物遭受干旱脅迫時(shí)，TaWRKY40與TaGAPC1啟動(dòng)子結(jié)合并增強(qiáng)啟動(dòng)子活性，從而增加ABA信號(hào)通路中的TaGAPC1基因表達(dá)水平，以增強(qiáng)植物抗旱性。Yan等[42]研究顯示，在干旱脅迫條件下，野生型棉花ABA誘導(dǎo)基因AREB、DREB、NCED、ERD和LEA的轉(zhuǎn)錄水平比轉(zhuǎn)基因植物抑制作用明顯，由此得到GhWRKY17通過ABA信號(hào)響應(yīng)干旱的結(jié)論。并且，過度表達(dá)活性ABA響應(yīng)元件結(jié)合蛋白AREB1和活化的AREB1（AREB1?QT）的植物能表現(xiàn)出更強(qiáng)的耐旱性[43]。

此外，F(xiàn)ei等[25]通過STRING預(yù)測(cè)表明WRKY還涉及3種激素信號(hào)通路——茉莉酸、水楊酸和乙烯信號(hào)通路。WRKY在激素的上下游發(fā)揮作用，參與水楊酸和茉莉酸/乙烯的拮抗作用，通過生長(zhǎng)素、細(xì)胞分裂素和油菜素甾醇類激素（BR）控制發(fā)育過程[9]，其中ZbWRKY33對(duì)干旱脅迫反應(yīng)強(qiáng)烈，主要依賴于茉莉酸信號(hào)通路為中心的調(diào)控網(wǎng)絡(luò)[25]。

1.3 WRKY調(diào)控植物發(fā)育和生理反應(yīng)抵御干旱脅迫

1.3.1 根

根系是植物吸收土壤水分和養(yǎng)分、感知和傳遞土壤水分虧缺信號(hào)的重要器官，植物通過更深的根系從更深的土壤剖面中提取水分的能力是干旱脅迫下直接影響產(chǎn)量的最相關(guān)特征之一[44]。BR除調(diào)節(jié)根系生長(zhǎng)發(fā)育還具有保護(hù)植物免受各種環(huán)境脅迫的能力[45]，Chen等[11]發(fā)現(xiàn)，一組WRKY轉(zhuǎn)錄因子WRKY46、WRKY54、WRKY70，其中WRKY54與BES1協(xié)同介導(dǎo)BR調(diào)節(jié)的干旱反應(yīng)，分別通過與W盒和G盒區(qū)域結(jié)合抑制干旱誘導(dǎo)基因GLYI7轉(zhuǎn)錄，而ABA會(huì)調(diào)節(jié)BIN2糖原合成酶激酶GSK-3抑制BR信號(hào)轉(zhuǎn)導(dǎo)，導(dǎo)致干旱脅迫下BIN2水平升高、WRKY54和BES1蛋白失穩(wěn)，最終導(dǎo)致干旱誘導(dǎo)基因的表達(dá)增加以抗旱生存。此外，WRKY轉(zhuǎn)錄因子可以和干旱誘導(dǎo)轉(zhuǎn)錄因子相互作用調(diào)節(jié)根系發(fā)育。Wang等[46]研究表明，GmWRKY27可與GmMYB174相互作用，通過抑制GmNAC29表達(dá)提高轉(zhuǎn)基因大豆毛狀根抗旱能力。而ZmWRKY40過表達(dá)激活干旱應(yīng)激反應(yīng)基因STZ、DREB和RD29A的表達(dá)促進(jìn)干旱脅迫下轉(zhuǎn)基因擬南芥根系生長(zhǎng)，降低水分流失率，提高了轉(zhuǎn)基因擬南芥的耐旱性[47]。

1.3.2 葉

葉片對(duì)干旱脅迫的形態(tài)和生理響應(yīng)是減少水分流失、提高水分利用效率的基礎(chǔ)[48]。在熱休克蛋白101啟動(dòng)子控制下，OsWRKY11過表達(dá)導(dǎo)致葉片萎蔫率降低，維持葉綠素和葉面積穩(wěn)定，這些因素有助于提高作物的耐旱性[49]。葉片中氣孔介導(dǎo)植物與大氣之間交換，其周圍保衛(wèi)細(xì)胞膨脹壓力的變化控制著氣孔開閉。

保衛(wèi)細(xì)胞轉(zhuǎn)錄組富含轉(zhuǎn)錄因子編碼基因，其中WRKY46已被證明參與調(diào)節(jié)光依賴性氣孔開放并調(diào)節(jié)干旱脅迫的反應(yīng)[50]。Sun等[51]研究表明，激活A(yù)tWRKY53表達(dá)可通過促進(jìn)淀粉代謝，促進(jìn)氣孔開放、調(diào)節(jié)氣孔運(yùn)動(dòng)，減少保衛(wèi)細(xì)胞中的H2O2含量，從而負(fù)調(diào)節(jié)干旱耐受性。但GmWRKY54可直接激活并結(jié)合PYL8、SRK2A、CIPK11及CPK3等基因，通過ABA和Ca2+信號(hào)通路促進(jìn)氣孔關(guān)閉，減少水分流失以賦予植株耐旱性[52]。

1.3.3 滲透調(diào)節(jié)和抗氧化反應(yīng)

轉(zhuǎn)錄因子本身在轉(zhuǎn)錄水平上受到其他上游成分調(diào)控，在轉(zhuǎn)錄后水平上經(jīng)過泛素化等修飾后，形成一個(gè)復(fù)雜的調(diào)控網(wǎng)絡(luò)，調(diào)節(jié)應(yīng)激反應(yīng)基因表達(dá)、各種生理和代謝過程。耐旱植物可通過積累蔗糖、海藻糖及棉子糖系列寡糖增強(qiáng)其抗旱性[53]，肌醇半乳糖苷合成酶（GolS）是棉子糖代謝過程中第一個(gè)限速步驟的關(guān)鍵酶。

Wang等[54]研究表明，BhGolS1賦予轉(zhuǎn)基因煙草脫水耐受性，未受脅迫的煙草中未檢測(cè)到半乳糖醇內(nèi)部積累，當(dāng)處于干旱脅迫環(huán)境時(shí)，WRKY轉(zhuǎn)錄因子與BhGolS1啟動(dòng)子的W盒結(jié)合導(dǎo)致轉(zhuǎn)基因煙草耐旱性提高。同樣，OsWRKY11能激活一些棉子糖合成相關(guān)基因表達(dá)，促進(jìn)植株體內(nèi)棉子糖的積累以抵御干旱脅迫[49]。此外，植物遭受干旱脅迫后，會(huì)伴隨次生脅迫損傷，如活性氧損傷，VlWRKY48在干旱脅迫下能提高過氧化氫酶、過氧化物酶、超氧化物歧化酶等抗氧化酶活性，清除活性氧（ROS）以提高葡萄抗旱性[14]。GhWRKY41/ SpWRKY1則調(diào)節(jié)氣孔導(dǎo)度和誘導(dǎo)抗氧化基因表達(dá)、降低丙二醛含量和ROS水平，提高轉(zhuǎn)基因煙草的耐旱性[55-56]。PbrWRKY53還能通過抗壞血酸途徑將H2O2轉(zhuǎn)化為H2O清除，減輕干旱造成的氧化損傷[39]。

2 WRKY參與植物次級(jí)代謝產(chǎn)物合成

根據(jù)化學(xué)成分，次生代謝產(chǎn)物大致分為兩類，即含氮分子（生物堿）和缺氮分子（萜類和酚類）。植物中生物堿、萜類、黃酮等化合物與植物逆境反應(yīng)有關(guān)，且干旱脅迫等逆境信號(hào)會(huì)誘導(dǎo)大量的轉(zhuǎn)錄因子形成調(diào)控網(wǎng)絡(luò)，其中WRKY轉(zhuǎn)錄因子可介導(dǎo)次生代謝產(chǎn)物在植物脅迫反應(yīng)中的作用[57]。見圖1。

許多植物合成的生物堿具有很高藥用價(jià)值，已被用于治療多種晚期疾病[58]。長(zhǎng)春花中大量萜類吲哚生物堿（TIA）是天然或半合成抗癌藥的重要來源，從其幼苗分離出的CrWRKY1被證明在TIA生物合成中起關(guān)鍵作用[59]。酚類化合物通常有一個(gè)帶有羥基的芳香環(huán)，其生物合成依賴于2條途徑（莽草酸途徑和丙二酸途徑），木質(zhì)素是該類群的重要成員[57]。已有研究表明，干旱會(huì)影響細(xì)胞壁木質(zhì)素的生物合成，擬南芥WRKY13通過直接結(jié)合NST2 18的啟動(dòng)子積極調(diào)節(jié)莖中木質(zhì)素生物合成[60]；此外，WRKY還控制黃酮醇和單寧化合物生成，WRKY23以生長(zhǎng)素誘導(dǎo)方式調(diào)節(jié)黃酮醇產(chǎn)生，實(shí)現(xiàn)根系正常生長(zhǎng)和發(fā)育[61]。

圖1 WRKY轉(zhuǎn)錄因子調(diào)控代謝途徑合成的植物化學(xué)物質(zhì)

萜類化合物具有多種生物學(xué)功能，丹參酮是一類具有生物活性的二萜類化合物，廣泛應(yīng)用于治療心血管疾病。Cao等[62]發(fā)現(xiàn)，SmWRKY1過度表達(dá)顯著提高M(jìn)EP途徑中編碼酶基因轉(zhuǎn)錄本，尤其1-脫氧-D-木糖-5-磷酸合成酶和1-脫氧-D-木酮糖-5-磷酸還原酶，使轉(zhuǎn)基因系中丹參酮產(chǎn)量提高5倍以上。并且，青蒿素中紫穗槐-4,11-二烯合酶（ADS）可催化法尼基焦磷酸轉(zhuǎn)化為紫穗槐-4,11-二烯1-羥化酶（CYP71AV1）。Ma等[63]研究表明，ADS是AaWRKY1靶基因，表明AaWRKY1參與了青蒿素生物合成調(diào)控，實(shí)現(xiàn)抗瘧藥青蒿素生物合成的第一步，且進(jìn)一步研究發(fā)現(xiàn)過表達(dá)的AaWRKY1激活了CYP71AV1轉(zhuǎn)錄，上調(diào)的CYP71AV1可促進(jìn)青蒿素生物合成。此外，過表達(dá)TcWRKY8和TcWRKY47能顯著提高紅豆杉中紫杉醇生物合成相關(guān)基因的表達(dá)水平，該成分是目前治療癌癥最有效的化療藥物[64]?？傊?，WRKY可正調(diào)控植物次級(jí)代謝產(chǎn)物合成與積累，有助于增強(qiáng)植株抗旱能力并發(fā)揮藥用價(jià)值。

3 小結(jié)

干旱脅迫會(huì)造成植物生長(zhǎng)不良和作物產(chǎn)量受限，是大部分植物生長(zhǎng)過程面臨的一種嚴(yán)重威脅因素，因此，必須通過一系列生理生化和分子應(yīng)激性反應(yīng)抵御干旱脅迫才能更好生存。轉(zhuǎn)錄調(diào)控對(duì)植物抗旱反應(yīng)起著至關(guān)重要作用，轉(zhuǎn)錄因子能調(diào)節(jié)干旱脅迫反應(yīng)途徑中一整套基因，近年來應(yīng)用RT-PCR、熒光定量PCR、基因芯片、酵母雙雜交等方法分析植物中WRKY家族在干旱脅迫下基因表達(dá)網(wǎng)絡(luò)的研究已成為熱點(diǎn)。盡管WRKY轉(zhuǎn)錄因子作為現(xiàn)代基因組工具對(duì)干旱脅迫耐受性的作用研究已取得重大進(jìn)展，但單個(gè)轉(zhuǎn)錄因子的完整調(diào)節(jié)機(jī)制，包括上下游的共同調(diào)節(jié)因子及其相互作用仍不清楚，未來可通過轉(zhuǎn)錄調(diào)控因子調(diào)控和活性，對(duì)馴化作物品種的遺傳改良，特別是抗逆性和防御反應(yīng)發(fā)揮作用；另外，WRKY能參與植物次級(jí)代謝產(chǎn)物調(diào)控，今后有必要深入研究干旱脅迫下WRKY調(diào)控植物次級(jí)代謝產(chǎn)物合成與積累機(jī)制，探索植物的藥用價(jià)值?？傊?，研究干旱脅迫下WRKY的響應(yīng)機(jī)制，進(jìn)一步闡明WRKY轉(zhuǎn)錄因子在植物抗旱中的作用，為后期應(yīng)用于植物的抗旱工程、培育抗旱新種質(zhì)，以及探索植物次生代謝產(chǎn)物藥用價(jià)值具有重要意義。

[1] ASHRAF M. Inducing drought tolerance in plants：recent advances[J]. Biotechnol Adv,2010,28(1)：169-183.

[2] ZHANG T, TAN D, ZHANG L, et al. Phylogenetic analysis and drought-responsive expression profiles of the WRKY transcription factor family in maize[J]. Agri Gene,2017,3：99-108.

[3] ZHANG Y, WANG L. The WRKY transcription factor superfamily：its origin in eukaryotes and expansion in plants[J]. BMC Evol Biol,2005,5(1)：1.

[4] ISHIGURO S, NAKAMURA K. Characterization of a cDNA encoding a novel DNA-binding protein, SPF1, that recognizes SP8 sequences in the 5′ upstream regions of genes coding for sporamin and β- amylase from sweet potato[J]. Mol Gen Genet,1994,244(6)：563-571.

[5] RUSHTON P J, MACDONALD H, HUTTLY A K, et al. Members of a new family of DNA-binding proteins bind to a conserved cis-element in the promoters of α-Amy2 genes[J]. Plant Mol Bio,1995,29(4)：691-702.

[6] RUSHTON P J , TORRES J T, PARNISKE M, et al. Interaction of elicitor-induced DNA-binding proteins with elicitor response elements in the promoters of parsley PR1 genes[J]. EMBO J, 1996,15(20)：5690-5700.

[7] EULGEM T, RUSHTON P J, ROBATZEK S, et al. The WRKY superfamily of plant transcription factors[J]. Trends in Plant Science,2000, 5(5)：199-206.

[8] YAMASAKI K, KIGAWA T, INOUE M, et al. Solution structure of an Arabidopsis WRKY DNA binding domain[J]. Plant Cell,2005,17(3)：944-956.

[9] TRIPATHI P, RABARA R C, RUSHTON P J. A systems biology perspective on the role of WRKY transcription factors in drought responses in plants[J]. Planta,2014,239(2)：255-266.

[10] BAKSHI M, OELMüLLER R. WRKY transcription factors：Jack of many trades in plants[J]. Plant Signal Behav,2014,9(2)：e27700.

[11] CHEN J, NOLAN T M, YE H, et al. Arabidopsis WRKY46, WRKY54, and WRKY70 transcription factors are involved in brassinosteroid- regulated plant growth and drought responses[J]. The Plant Cell, 2017,29(6)：1425-1439.

[12] JIANG Y, LIANG G, YU D. Activated expression of WRKY57 confers drought tolerance in Arabidopsis[J]. Mol Plant,2012,5(6)：1375- 1388.

[13] MENG D, LI Y, BAI Y, et al. Genome-wide identification and characterization of WRKY transcriptional factor family in apple and analysis of their responses to waterlogging and drought stress[J]. Plant Physi Biochem,2016,103：71-83.

[14] ZHAO J, ZHANG X, GUO R, et al. Over-expression of a grape WRKY transcription factor gene, VlWRKY48, in Arabidopsis thaliana increases disease resistance and drought stress tolerance[J]. Plant Cell, Tissue and Organ Culture,2018,132(2)：359-370.

[15] ZHU D, CHE Y, XIAO P, et al. Functional analysis of a grape WRKY30 gene in drought resistance[J]. Plant Cell, Tissue and Organ Culture,2018,132(3)：449-459.

[16] RUSHTON P J, SOMSSICH I E, RINGLER P, et al. WRKY transcription factors[J]. Trends Plant Sci,2010,15(5)：247-258.

[17] HE G H, XU J Y, WANG Y X, et al. Drought-responsive WRKY transcription factor genes TaWRKY1 and TaWRKY33 from wheat confer drought and/or heat resistance in Arabidopsis[J]. BMC Plant Biol,2016,16(1)：116.

[18] SHEN H, LIU C, ZHANG Y, et al. OsWRKY30 is activated by MAP kinases to confer drought tolerance in rice[J]. Plant Mol Biol, 2012,80(3)：241-253.

[19] TAO Z, KOU Y, LIU H, et al. OsWRKY45 alleles play different roles in abscisic acid signalling and salt stress tolerance but similar roles in drought and cold tolerance in rice[J]. J Exp Bot,2011, 62(14)：4863-4874.

[20] CAI R H, ZHAO Y, WANG Y F, et al. Overexpression of a maize WRKY58 gene enhances drought and salt tolerance in transgenic rice[J]. Plant Cell, Tissue and Organ Culture,2014,119(3)：565-577.

[21] RABARA R C, TRIPATHI P, REESE R N, et al. Tobacco drought stress responses reveal new targets for Solanaceae crop improvement[J]. BMC Genomics,2015,16(1)：484.

[22] TANG L, CAI H, ZHAI H, et al. Overexpression of Glycine soja WRKY20 enhances both drought and salt tolerance in transgenic alfalfa (L.)[J]. Plant Cell, Tissue and Organ Culture,2014,118(1)：77-86.

[23] LIU L, ZHANG Z, DONG J, et al. Overexpression of MtWRKY76 increases both salt and drought tolerance in Medicago truncatula[J]. Environmental ＆ Experimental Botany,2016,123：50-58.

[24] JAFFAR M A, SONG A, FAHEEM M, et al. Involvement of CmWRKY10 in drought tolerance of chrysanthemum through the ABA-signaling pathway[J]. Int J Mol Sci,2016,17(5)：693.

[25] FEI X, HOU L, SHI J, et al. Patterns of drought response of 38 WRKY transcription factors of zanthoxylum bungeanum maxim[J]. Int J Mol Sci,2019,20(1)：68.

[26] ?AHIN-?EVIK M. A WRKY transcription factor gene isolated fromshows differential responses to cold and drought stresses[J]. Plant Omics,2012,5(5)：438-445.

[27] HUANG X, LI K, XU X, et al. Genome-wide analysis of WRKY transcription factors in white pear () reveals evolution and patterns under drought stress[J]. BMC Genomics,2015,16：1104.

[28] ZHU H, ZHOU Y, ZHAI H, et al. A novel sweetpotato WRKY transcription factor, IbWRKY2, positively regulates drought and salt tolerance in transgenic Arabidopsis[J]. Biomolecules,2020, 10(4)：506.

[29] WANG F, HOU X, TANG J, et al. A novel cold-inducible gene from Pak-choi (ssp. chinensis), BcWRKY46, enhances the cold, salt and dehydration stress tolerance in transgenic tobacco[J]. Mol Biol Rep,2012,39(4)：4553-4564.

[30] KIRANMAI K, LOKANADHA R G, PANDURANGAIAH M, et al. A novel WRKY transcription factor, MuWRKY3 (Lam. Verdc.) enhances drought stress tolerance in transgenic groundnut (L.) plants[J]. Front Plant Sci,2018,9：346-346.

[31] KHAN S A, LI M Z, WANG S M, et al. Revisiting the role of plant transcription factors in the battle against abiotic stress[J]. Int J Mol Sci,2018,19(6)：1634.

[32] KARKUTE S G, GUJJAR R S, RAI A, et al. Genome wide expression analysis of WRKY genes in tomato () under drought stress[J]. Plant Gene,2018,13：8-17.

[33] ZHOU Y, YANG Y, ZHOU X, et al. Structural and functional characterization of the VQ protein family and VQ protein variants from soybean[J]. Sci Rep,2016,6(1)：34663.

[34] BIGEARD J, HIRT H. Nuclear signaling of plant MAPKs[J]. Front Plant Sci,2018,9：469.

[35] SHEIKH A H, ESCHEN-LIPPOLD L, PECHER P, et al. Regulation of WRKY46 transcription factor function by mitogen-activated protein kinases in Arabidopsis thaliana[J]. Front Plant Sci, 2016,7：61.

[36] BARTELS D, SUNKAR R. Drought and salt tolerance in plants[J]. Critical Reviews in Plant Sciences,2005,24(1)：23-58.

[37] LI F, LI M, WANG P, et al. Regulation of cotton (Gossypium hirsutum) drought responses by mitogenactivated protein (MAP) kinase cascade-mediated phosphorylation of Gh WRKY 59[J]. New Phytologist,2017,215(4)：1462-1475.

[38] ULLAH A, MANGHWAR H, SHABAN M, et al. Phytohormones enhanced drought tolerance in plants：a coping strategy[J]. Environ Sci Pollut Res Int,2018,25(33)：33103-33118.

[39] LIU Y, YANG T, LIN Z. et al. A WRKY transcription factor PbrWRKY53 from pyrus betulaefolia is involved in drought tolerance and AsA accumulation[J]. Plant Biotechnology Journal, 2019,17(9)：1770-1787.

[40] UMEZAWA T, OKAMOTO M, KUSHIRO T, et al. CYP707A3, a major ABA 8'-hydroxylase involved in dehydration and rehydration response in Arabidopsis thaliana[J]. Plant J,2006,46(2)：171-182.

[41] ZHANG L, XU Z, JI H, et al. TaWRKY40 transcription factor positively regulate the expression of TaGAPC1 to enhance drought tolerance[J]. BMC Genomics,2019,20(1)：795.

[42] YAN H, JIA H, CHEN X, et al. The cotton WRKY transcription factor GhWRKY17 functions in drought and salt stress in transgenic Nicotiana benthamiana through ABA signaling and the modulation of reactive oxygen species production[J]. Plant Cell Physiol, 2014,55(12)：2060-2076.

[43] LEITE J P, BARBOSA E G, MARIN S R, et al. Overexpression of the activated form of the AtAREB1 gene (AtAREB1ΔQT) improves soybean responses to water deficit[J]. Genet Mol Res,2014,13(3)：6272-6286.

[44] MOUMENI A, SATOH K, KONDOH H, et al. Comparative analysis of root transcriptome profiles of two pairs of drought-tolerant and susceptible rice near-isogenic lines under different drought stress[J]. BMC Plant Biol,2011,11(1)：174.

[45] ANWAR A, LIU Y, DONG R, et al. The physiological and molecular mechanism of brassinosteroid in response to stress：a review[J]. Biological Res,2018,51(1)：46.

[46] WANG F, CHEN H W, LI Q T, et al. Gm WRKY 27 interacts with Gm MYB 174 to reduce expression of Gm NAC 29 for stress tolerance in soybean plants[J]. Plant J,2015,83(2)：224-236.

[47] WANG C T, RU J N, LIU Y W, et al. The maize WRKY transcription factor ZmWRKY40 confers drought resistance in transgenic Arabidopsis[J]. Int J Mol Sci,2018,19(9)：2580.

[48] BALDONI E, GENGA A, COMINELLI E. Plant MYB transcription factors：their role in drought response mechanisms[J]. Int J Mol Sci,2015,16(7)：15811-15851.

[49] WU X, SHIROTO Y, KISHITANI S, et al. Enhanced heat and drought tolerance in transgenic rice seedlings overexpressing OsWRKY11 under the control of HSP101 promoter[J]. Plant Cell Rep,2009, 28(1)：21-30.

[50] DING Z J, YAN J Y, XU X Y, et al. Transcription factor WRKY 46 regulates osmotic stress responses and stomatal movement independently in Arabidopsis[J]. Plant J,2014,79(1)：13-27.

[51] SUN Y, YU D. Activated expression of AtWRKY53 negatively regulates drought tolerance by mediating stomatal movement[J]. Plant Cell Rep,2015,34(8)：1295-1306.

[52] WEI W, LIANG D W, BIAN X H, et al. GmWRKY54 improves drought tolerance through activating genes in abscisic acid and Ca2+signaling pathways in transgenic soybean[J]. Plant J,2019, 100(2)：384-398.

[53] ALBINI F M, MURELLI C, FINZI P V, et al.Galactinol in the leaves of the resurrection plant Boea hygroscopica[J]. Phytochemistry, 1999,51(4)：499-505.

[54] WANG Z, ZHU Y, WANG L, et al. A WRKY transcription factor participates in dehydration tolerance in Boea hygrometrica by binding to the W-box elements of the galactinol synthase (BhGolS1) promoter[J]. Planta,2009,230(6)：1155-1166.

[55] CHU X, WANG C, CHEN X, et al. The cotton WRKY gene GhWRKY41 positively regulates salt and drought stress tolerance in transgenic Nicotiana benthamiana[J]. PLoS One,2015,10(11)：e0143022.

[56] LI J B, LUAN Y S, LIU Z. Overexpression of SpWRKY1 promotes resistance to Phytophthora nicotianae and tolerance to salt and drought stress in transgenic tobacco[J]. Physiol Plant,2015, 155(3)：248-266.

[57] MERAJ T A, FU J, RAZA M A, et al. Transcriptional factors regulate plant stress responses through mediating secondary metabolism[J]. Genes (Basel),2020,11(4)：346.

[58] PATRA B, SCHLUTTENHOFER C, WU Y. et al. Transcriptional regulation of secondary metabolite biosynthesis in plants[J]. Biochim Biophys Acta,2013,1829(11)：1236-1247.

[59] SUTTIPANTA N, PATTANAIK S, KULSHRESTHA M, et al. The transcription factor CrWRKY1 positively regulates the terpenoid indole alkaloid biosynthesis in Catharanthus roseus[J]. Plant Physiol,2011,157(4)：2081-2093.

[60] LI W, TIAN Z, YU D. WRKY13 acts in stem development in Arabidopsis thaliana[J]. Plant Sci,2015,236：205-213.

[61] GRUNEWALD W, DE SMET I, LEWIS D R, et al. Transcription factor WRKY23 assists auxin distribution patterns during Arabidopsis root development through local control on flavonol biosynthesis[J]. Proc Natl Acad Sci USA,2012,109(5)：1554-1559.

[62] CAO W, WANG Y, SHI M, et al. Transcription factor SmWRKY1 positively promotes the biosynthesis of tanshinones in salvia miltiorrhiza[J]. Front Plant Sci,2018,9：554.

[63] MA D, PU G, LEI C, et al. Isolation and characterization of AaWRKY1, an Artemisia annua transcription factor that regulates the amorpha-4,11-diene synthase gene, a key gene of artemisinin biosynthesis[J]. Plant Cell Physiol,2009,50(12)：2146-2161.

[64] ZHANG M, CHEN Y, NIE L, et al. Transcriptome-wide identification and screening of WRKY factors involved in the regulation of taxol biosynthesis in Taxus chinensis[J]. Sci Rep,2018,8(1)：5197.

Research Progress in the Role of WRKY Transcription Factor inPlant Drought Response Mechanism

SUN Xiaochen, LI Jinpeng, YUAN Jingjing, WANG Huizhen, DU Tao

WRKY transcription factor is the main regulator that regulates plant development and responds to external stress stimuli, and plays an important role in the process of plant resistance to drought. This article summarized the research on the signal pathways that WRKY transcription factors rely on to resist drought stress, the plant growth and physiological regulation under drought stress, and the regulation of secondary metabolites of medicinal plants, in order to provide references for further exploring the molecular mechanism of drought resistance in plants, cultivating drought-tolerant strains, and exploring the medicinal value of plant secondary metabolites.

WRKY transcription factor; drought stress; signal pathway; growth and development; secondary metabolites; review

R2-05；R282.5

A

1005-5304(2021)06-0138-07

10.19879/j.cnki.1005-5304.202007627

國(guó)家自然科學(xué)基金（81760683）；現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)體系建設(shè)專項(xiàng)（CARS-21）

王惠珍，E-mail：whz1974828@163.com

（2020-07-31）

（2020-11-09；編輯：梅智勝）