劉昌云,李欣羽,田紹銳,王靖,裴悅宏,馬小舟,2,樊光進(jìn),汪代斌,孫現(xiàn)超
番茄的克隆、表達(dá)與抗病毒功能
劉昌云1,李欣羽1,田紹銳1,王靖1,裴悅宏1,馬小舟1,2,樊光進(jìn)1,汪代斌3*,孫現(xiàn)超1*
1西南大學(xué)植物保護(hù)學(xué)院,重慶 400715;2西南大學(xué)園藝園林學(xué)院南方山地園藝學(xué)教育部重點(diǎn)實(shí)驗(yàn)室,重慶 400715;3重慶煙草科學(xué)研究所,重慶400715
【目的】番茄()作為重要的蔬菜作物,其生長(zhǎng)受到包括害蟲(chóng)、真菌、細(xì)菌和病毒等各種生物因素的危害。明確番茄抗性基因的抗病毒功能與機(jī)制,為番茄的抗病毒育種與抗病毒藥劑的靶向開(kāi)發(fā)提供理論依據(jù)。【方法】從茄科植物基因組數(shù)據(jù)庫(kù)Solanaceae Genomics Network中獲得的全長(zhǎng),并將其分為4段,利用融合聚合酶鏈?zhǔn)椒磻?yīng)(fusion PCR)擴(kuò)增獲得的序列全長(zhǎng);通過(guò)生物信息學(xué)分析SlN-like的進(jìn)化關(guān)系、蛋白特征、保守結(jié)構(gòu)域、亞細(xì)胞定位以及互作關(guān)系;通過(guò)實(shí)時(shí)熒光定量PCR分析在番茄根、莖、葉、花和果實(shí)中的表達(dá)情況及其在煙草花葉病毒(tobacco mosaic virus,TMV)侵染后的葉片表達(dá)量;借助煙草脆裂病毒(tobacco rattle virus,TRV)介導(dǎo)的基因沉默技術(shù)(virus induced gene silencing,VIGS)沉默番茄內(nèi)源,摩擦接種TMV-GFP于沉默植株,明確對(duì)病毒侵染的影響。實(shí)時(shí)熒光定量PCR分析沉默植株中脫落酸(abscisic acid)、茉莉酸(jasmonic acid)和乙烯(ethylene)激素相關(guān)基因的表達(dá)量及在外施乙烯利(ethephon,ETH)3、6、12、24 h后的表達(dá)情況,最終明確SlN-like調(diào)控激素途徑響應(yīng)病毒侵染的機(jī)制?!窘Y(jié)果】通過(guò)分子克隆與融合PCR技術(shù),從番茄品種Micro-Tom中克隆獲得全長(zhǎng)3 444 bp的,上傳至NCBI獲得序列號(hào)MW792493。通過(guò)生物信息學(xué)分析發(fā)現(xiàn)SlN-like含有TIR、NB-ARC和NACHT結(jié)構(gòu)域,并與馬鈴薯()N-like(AAP44394.1)親緣關(guān)系最近。在番茄各組織中均有表達(dá),在莖中的表達(dá)量最高,其次是根、花,葉和果實(shí)中的表達(dá)量最低。TMV-GFP侵染番茄后第5、7天的表達(dá)顯著高于PBS處理,分別是PBS處理的1.6和2.2倍,并且TMV-GFP侵染會(huì)使的表達(dá)持續(xù)升高。TRV載體介導(dǎo)沉默番茄的,發(fā)現(xiàn)沉默78.3%的不會(huì)影響番茄生長(zhǎng)表型,但可促進(jìn)TMV-GFP侵染;實(shí)時(shí)熒光定量PCR分析發(fā)現(xiàn)沉默植株中的表達(dá)顯著降低,僅為對(duì)照組的12.5%;外施乙烯利處理番茄3 h后表達(dá)量升高,并在12 h達(dá)到最高峰,是對(duì)照組的2.71倍,24 h后恢復(fù)正常?!窘Y(jié)論】番茄SlN-like屬NBS-LRR類(lèi)抗病蛋白,其表達(dá)受TMV侵染誘導(dǎo),沉默促進(jìn)TMV-GFP侵染,降低乙烯相關(guān)基因的表達(dá),而外施乙烯利導(dǎo)致的差異表達(dá),揭示了SlN-like作為正調(diào)控因子可能影響乙烯途徑介導(dǎo)的番茄抗病毒防御。
番茄;SlN-like;煙草花葉病毒;基因表達(dá);乙烯
【研究意義】番茄()是茄科番茄屬的一種一年生或多年生草本植物,在農(nóng)業(yè)種植方面有著重要的地位。生產(chǎn)過(guò)程中,番茄會(huì)遭受高溫、干旱等非生物脅迫或病毒、真菌等生物脅迫,造成生物組織的損傷,進(jìn)而引起減產(chǎn)。其中由煙草花葉病毒(tobacco mosaic virus,TMV)引起的番茄病毒病是番茄生產(chǎn)過(guò)程的重要病害之一。挖掘并研究番茄抗病毒基因及其抗病毒機(jī)制,對(duì)番茄抗病毒育種及利用藥劑誘導(dǎo)調(diào)控抗病毒基因防控病毒病具有重要意義?!厩叭搜芯窟M(jìn)展】是最早發(fā)現(xiàn)的抗TMV基因,煙草可對(duì)包括TMV、番茄花葉病毒(tomato mosaic virus,ToMV)在內(nèi)的絕大多數(shù)煙草花葉病毒組成員產(chǎn)生抗性,屬TIR-NBS-LRR類(lèi)植物抗性基因家族中的一員[1-2]。早期研究發(fā)現(xiàn),TMV復(fù)制酶126 kD能夠引起介導(dǎo)的超敏反應(yīng)(hypersensitivity,HR)[3],而位于復(fù)制酶126 kD羧基端末端的約50 kD的解旋酶片段(p50)能夠?qū)е罗D(zhuǎn)錄產(chǎn)物的積累,并有效地引起介導(dǎo)的HR反應(yīng)[4-5],因此編碼p50的核苷酸序列又被稱(chēng)為對(duì)應(yīng)的無(wú)毒基因(avirulence,)。TMV侵染引起心葉煙()、三生煙(var.Samsun NN)等抗病品種壞死斑的形成是植物體自身防御病原微生物侵入所形成的細(xì)胞程序性死亡(programmed cell death,PCD)[6]。目前介導(dǎo)的TMV識(shí)別過(guò)程及其對(duì)下游抗病基因的誘導(dǎo)已經(jīng)研究得非常透徹[7]。NRIP1(N receptor- interacting protein 1)是一種同時(shí)與N蛋白的TIR結(jié)構(gòu)域和p50產(chǎn)生相互作用的硫氰酸酶(硫轉(zhuǎn)移酶),NRIP1定位于葉綠體中。SPL6(squamosa promoter binding protein-like 6)是一種與N蛋白在核小體內(nèi)互作的轉(zhuǎn)錄因子。在TMV未侵染的細(xì)胞中,N蛋白處于活性被抑制的狀態(tài),其表達(dá)極低,并且分布在細(xì)胞核和細(xì)胞質(zhì)中[8]。此時(shí)核內(nèi)的N蛋白不與SPL6結(jié)合。當(dāng)TMV通過(guò)機(jī)械損傷進(jìn)入植物體內(nèi)后,病毒在細(xì)胞質(zhì)中脫殼、復(fù)制、轉(zhuǎn)錄和翻譯,p50激發(fā)子引起了NRIP1的重新定位。NRIP1與p50結(jié)合后,被細(xì)胞質(zhì)中的N蛋白識(shí)別,三者形成NRIP1-p50-N復(fù)合體[9]。隨著三者的結(jié)合,p50引起了N蛋白構(gòu)象上的變化,而該變化可能需要ATP結(jié)合或水解。結(jié)合ATP的N蛋白進(jìn)入細(xì)胞核,與SPL6互作進(jìn)而引起SPL6的轉(zhuǎn)錄激活功能,激活了下游抗性基因的表達(dá)[10]。此外,NRIP1-p50-N形成復(fù)合體的同時(shí),N蛋白利用其LRR結(jié)構(gòu)域與p50形成次級(jí)結(jié)合,釋放出TIR-NBS區(qū)段以提高核酸結(jié)合能力,促成N蛋白的聚合。聚合后的N蛋白進(jìn)入核內(nèi),與SPL6結(jié)合,激活并引起下游抗性基因的表達(dá)[11]?!颈狙芯壳腥朦c(diǎn)】是的同源基因,同樣含有TIR-NBS-LRR結(jié)構(gòu)域,其TIR-NBS保守結(jié)構(gòu)域區(qū)段同樣可與TMV p50產(chǎn)生HR反應(yīng),而LRR并不能和p50產(chǎn)生HR反應(yīng)[12],因此推測(cè)這可能與N-like與TMV的識(shí)別有關(guān)[13],并且可能行駛的第一種調(diào)控模式。但番茄中如何響應(yīng)病毒侵染,如何調(diào)控寄主免疫防御知之甚少[14-15]?!緮M解決的關(guān)鍵問(wèn)題】通過(guò)克隆番茄抗性基因的cDNA全長(zhǎng),并對(duì)核酸序列和蛋白質(zhì)序列進(jìn)行生物信息學(xué)分析,利用實(shí)時(shí)熒光定量PCR技術(shù)明確的表達(dá)模式,通過(guò)病毒介導(dǎo)的基因沉默(virus-induced gene silencing,VIGS)分析對(duì)TMV-GFP侵染的影響,確定SlN-like的抗病功能,并明確SlN-like可能影響的激素通路,為解析SlN-like在番茄抗病應(yīng)答中的調(diào)控機(jī)制提供科學(xué)依據(jù),同時(shí)為番茄抗病品種的選育和抗病毒藥劑的靶向開(kāi)發(fā)提供理論依據(jù)。
試驗(yàn)于2020—2021年在西南大學(xué)植物保護(hù)學(xué)院植物免疫與植物病害生態(tài)防控實(shí)驗(yàn)室完成。
1.1.1 供試菌株與植物 供試大腸桿菌()DH5和農(nóng)桿菌()GV3101購(gòu)自上海唯地生物技術(shù)有限公司;VIGS沉默載體和煙草花葉病毒熒光標(biāo)記載體TMV-GFP(pSDK661)由清華大學(xué)劉玉樂(lè)教授課題組饋贈(zèng);供試番茄Micro-Tom品種在恒溫培養(yǎng)室中播種,培養(yǎng)至4—6葉期左右備用。
1.1.2 試劑和引物 DNA純化回收試劑盒和質(zhì)粒提取試劑盒購(gòu)自擎科興業(yè)生物技術(shù)有限公司;總RNA提取劑、反轉(zhuǎn)錄試劑盒、高保真酶PrimeSTAR? GXL DNA Polymerase DNA聚合酶、T4 DNA連接酶購(gòu)自大連TaKaRa公司;實(shí)時(shí)熒光定量試劑盒購(gòu)自莫納生物。引物和測(cè)序由上海生工生物工程公司完成。
番茄Micro-Tom總RNA提取按照TaKaRa RNAisoPlus(Total RNA 提取試劑)試劑盒手冊(cè)進(jìn)行。根據(jù)茄科植物基因組數(shù)據(jù)庫(kù)Solanaceae Genomics Network[16](https://solgenomics.net/)中預(yù)測(cè)到的番茄序列,將其分為4段分段擴(kuò)增,引物詳見(jiàn)表1。以Micro-Tom番茄的cDNA為模板,擴(kuò)增獲得4段PCR片段,并利用融合PCR將4段片段融合。將序列上傳至NCBI,獲得序列號(hào)。運(yùn)用ExPASy ProtParam(https://web.expasy.org/protparam/)分析SlN-like的蛋白理化性質(zhì),TMHMM 2.0(http://www.cbs.dtu.dk/ services/)分析SlN-like的跨膜區(qū)域,Cell-PLoc 2.0(http://www.csbio.sjtu.edu.cn/bioinf/Cell-PLoc-2/)預(yù)測(cè)SlN-like的亞細(xì)胞定位[17],STRING(https://string- db.org/)分析SlN-like的互作網(wǎng)絡(luò),SMART(http:// smart.embl-heidelberg.de/)分析SlN-like的保守結(jié)構(gòu)域,NCBI Blastp比對(duì)出與番茄SlN-like同源的N-like蛋白,利用MEGA X分析并制茄科植物N-like系統(tǒng)進(jìn)化樹(shù)。
表1 本研究所用到的引物
下劃線的堿基為所加酶切位點(diǎn) The underlined bases were the restriction enzyme sites
TMV接種方法詳見(jiàn)文獻(xiàn)[18]。將0.1 g帶有TMV-GFP的鮮樣葉片放置研缽中,加入石英砂,并使用pH 7.2—7.4的磷酸緩沖液研磨至勻漿狀。獲得的勻漿在5 000×離心機(jī)中離心3 min,取上清進(jìn)行摩擦接種。每片葉片接種100 μL,每株植株接種兩片葉。
沉默載體的構(gòu)建基于煙草脆裂病毒(tobacco rattle virus,TRV)改造的沉默體系。首先根據(jù)的全長(zhǎng),利用Solanaceae Genomics Network的VIGS Tool(https://vigs.solgenomics.net/)分析獲得的最佳沉默片段,設(shè)計(jì)含有H I和I的沉默片段引物,將其連接在同樣被H I和I雙酶切的pTRV2載體上,構(gòu)建pTRV2:SlN-like載體。以空載體pTRV2為對(duì)照,將pTRV1和pTRV2:SlN-like轉(zhuǎn)化至農(nóng)桿菌GV3101中,過(guò)夜培養(yǎng)至OD600=0.6,等比混合后接種六葉期番茄。14 d后利用實(shí)時(shí)熒光定量PCR檢測(cè)沉默效率。
實(shí)時(shí)熒光定量PCR利用qTOWER2.0 real-time PCR(Analytikjena,Germany)和MonAmpTMChemoHS qPCR Mix(Monad,China)分析靶基因的相對(duì)表達(dá)水平。使用Primer3web(https://bioinfo.ut.ee/primer3/)軟件根據(jù)每個(gè)基因的編碼序列設(shè)計(jì)基因特異性引物。選擇番茄作為內(nèi)參,使用2-ΔΔCt法定量計(jì)算基因轉(zhuǎn)錄水平的相對(duì)變化[19-20]。
六葉期番茄噴施100 mmol·L-1的乙烯利(Aladdin),以噴施無(wú)菌水為對(duì)照,并在3、6、12、24 h取樣,保存至-80℃冰箱用于下步試驗(yàn)。
所有試驗(yàn)和數(shù)據(jù)至少3個(gè)重復(fù),數(shù)據(jù)表示為平均值±標(biāo)準(zhǔn)誤(SE),統(tǒng)計(jì)分析采用SPSS軟件student’s檢驗(yàn)(*0.01<<0.05,**0.001<<0.01,***<0.001)和ANOVA單因素分析(LSD檢驗(yàn),<0.05)。
首先根據(jù)本氏煙TMV,在茄科植物基因組數(shù)據(jù)庫(kù)Sol Network中比對(duì)出番茄的可能序列。根據(jù)序列結(jié)構(gòu)將預(yù)測(cè)的番茄核苷酸分為4段,命名為P1—P4,長(zhǎng)度分別為493、1 132、1 357和529 bp。以番茄Micro-Tom品種cDNA為模板,分別擴(kuò)增4段片段,長(zhǎng)度和預(yù)測(cè)相符,總長(zhǎng)度3 444 bp,命名為。上傳至NCBI,獲得序列號(hào)MW792493。編碼蛋白共1 147個(gè)氨基酸,ProtParam預(yù)測(cè)結(jié)果顯示其理論分子量為130.48 kD,理論等電點(diǎn)為8.74,分子式為C5866H9357N1575O1671S56。TMHMM 2.0分析結(jié)果顯示SlN-like不具有跨膜結(jié)構(gòu)。Cell-PLoc 2.0亞細(xì)胞定位預(yù)測(cè)結(jié)果表明SlN-like可能定位于細(xì)胞質(zhì)與細(xì)胞膜。STRING互作蛋白預(yù)測(cè)顯示SlN-like可能與線粒體小核糖體亞基蛋白(mitochondrial small ribosomal subunit protein,Solyc01g081520.2.1)、半胱氨酸蛋白酶抑制劑(cysteine proteinase inhibitor,Solyc09g097850.1.1)、五肽重復(fù)PPR超家族蛋白(pentatricopeptide repeat superfamily protein,Solyc05g047540.2.1)和EDS1(enhanced disease susceptibility 1,Solyc06g071280.2.1)等蛋白存在互作。SMART預(yù)測(cè)SlN-like保守結(jié)構(gòu)域表明SlN-like含有TIR、NB-ARC和NACHT保守結(jié)構(gòu)域,為NBS-LRR類(lèi)抗病蛋白。
根據(jù)SlN-like的氨基酸序列,在NCBI對(duì)比茄科植物中的SlN-like同源蛋白。下載茄科植物中10個(gè)物種的N-like氨基酸序列,利用MEGA X構(gòu)建進(jìn)化樹(shù)。由圖1可知,SlN-like與馬鈴薯()N-like(AAP44394.1)的氨基酸親緣關(guān)系最近,與野生煙草()N-like(AKN63563.1)和中華辣椒()N-like(PHU14921.1)的親緣關(guān)系較遠(yuǎn)。
利用實(shí)時(shí)熒光定量PCR檢測(cè)在根、莖、葉、花和果實(shí)各組織中的表達(dá)量。結(jié)果顯示,在莖中的表達(dá)量最高,其次是花和根,在葉和果實(shí)中的表達(dá)量最低(圖2-A),表明表達(dá)具有組織差異性。為進(jìn)一步明確在TMV侵染番茄過(guò)程中的表達(dá),以PBS為對(duì)照,摩擦接種TMV-GFP,并于接種后第3、5、7天取樣,利用實(shí)時(shí)熒光定量PCR檢測(cè)TMV-GFP侵染番茄Micro-Tom后的表達(dá)量。結(jié)果顯示,TMV-GFP侵染后3 d,處理組中的表達(dá)是對(duì)照組的1.4倍,但差異不顯著。TMV-GFP侵染后5、7 d,處理組中的表達(dá)顯著高于對(duì)照,分別為是對(duì)照組的1.6、2.2倍。TMV-GFP侵染后呈現(xiàn)表達(dá)逐漸上升趨勢(shì)(圖2-B),說(shuō)明TMV-GFP侵染會(huì)誘導(dǎo)的表達(dá),揭示SlN-like可能參與番茄抗TMV響應(yīng)。
為進(jìn)一步明確對(duì)TMV-GFP侵染的影響,利用TRV介導(dǎo)的基因沉默技術(shù)沉默番茄內(nèi)源。以TRV:00為對(duì)照,沉默14 d后,發(fā)現(xiàn)沉默植株與對(duì)照植株相比并無(wú)顯著的表型差異(圖3-A),說(shuō)明沉默不會(huì)影響番茄生長(zhǎng);沉默效率檢測(cè)表明,TRV:SlN-like植株中的表達(dá)量?jī)H為對(duì)照的21.7%(圖3-B),說(shuō)明成功沉默。
圖1 SlN-like及其同源基因系統(tǒng)發(fā)育分析
A:SlN-like的組織表達(dá),統(tǒng)計(jì)分析采用ANOVA(LSD檢測(cè),P<0.05)Tissue expression of SlN-like, the statistical analyses were performed using One-way ANOVA (LSD’s test, P<0.05);B:TMV侵染后SlN-like的表達(dá)。統(tǒng)計(jì)分析采用Student’s t檢驗(yàn)(**0.001<P<0.01,***P<0.001),每個(gè)處理進(jìn)行3次生物學(xué)重復(fù),每次生物學(xué)重復(fù)3株番茄,數(shù)值代表3次生物學(xué)重復(fù)的平均值±標(biāo)準(zhǔn)誤SlN-like expression after TMV infection.The statistical analyses were performed using Student’s t-test (**0.001<P<0.01, ***P<0.001).The experiments were repeated three times with three plants each time.Values represent means±SE from three biological replications
A:SlN-like沉默后的番茄表型Tomato phenotype after SlN-like silenced;B:TRV:SlN-like的沉默效率檢測(cè)。統(tǒng)計(jì)分析采用Student’s t檢驗(yàn) (***P<0.001),每個(gè)處理進(jìn)行3次生物學(xué)重復(fù),每次生物學(xué)重復(fù)10株番茄,數(shù)值代表3次生物學(xué)重復(fù)的平均值±標(biāo)準(zhǔn)誤silencing efficiency detection in TRV:SlN-like.The statistical analyses were performed using Student’s t-test (***P<0.001).The experiments were repeated three times with ten plants each time.Values represent means±SE from three biological replications
對(duì)成功沉默的植株進(jìn)行攻毒試驗(yàn)。接種TMV-GFP于沉默植株TRV:SlN-like和對(duì)照組TRV:00,于接種后第3、5、7天在手持紫外燈下觀察TMV-GFP的熒光斑點(diǎn)數(shù)(圖4-A),并取樣利用實(shí)時(shí)熒光定量PCR對(duì)TMV進(jìn)行定量分析,明確沉默后TMV-GFP的侵染情況(圖4-B)。結(jié)果顯示,沉默后接種TMV-GFP第3、5天時(shí),沉默植株中接種葉的熒光斑點(diǎn)數(shù)明顯多于對(duì)照植株,實(shí)時(shí)熒光定量PCR也顯示同樣結(jié)果。沉默后接種TMV-GFP第7天,實(shí)時(shí)熒光定量PCR表明沉默植株系統(tǒng)葉中TMV的含量顯著高于對(duì)照組,為對(duì)照的4.58倍,說(shuō)明沉默會(huì)促進(jìn)TMV-GFP侵染,SlN-like可能作為正調(diào)控因子抑制TMV-GFP侵染。
A:TRV:SlN-like和TRV:00接種TMV-GFP后的癥狀圖Symptoms after inoculation with TMV-GFP in TRV:SlN-like and TRV:00;B:TRV:SlN-like和TRV:00中TMV MP含量檢測(cè)。統(tǒng)計(jì)分析采用Student’s t檢驗(yàn)(**0.001<P<0.01,***P<0.001),每個(gè)處理進(jìn)行3次生物學(xué)重復(fù),每次生物學(xué)重復(fù)10株番茄,數(shù)值代表3次生物學(xué)重復(fù)的平均值±標(biāo)準(zhǔn)誤 Detection of TMV MP content in TRV:SlN-like and TRV:00.The statistical analyses were performed using Student’s t-test (**0.001<P<0.01, ***P<0.001).The experiments were repeated three times with ten plants each time.Values represent means±SE from three biological replications
為探討SlN-like參與抗病毒防御的機(jī)制,以TRV:00為對(duì)照,對(duì)沉默植株中乙烯(ethylene,ET)相關(guān)基因、脫落酸(abscisic acid,ABA)相關(guān)基因以及茉莉酸(jasmonic acid,JA)相關(guān)基因的表達(dá)進(jìn)行實(shí)時(shí)熒光定量PCR分析。結(jié)果顯示,沉默后,乙烯途徑相關(guān)基因的表達(dá)量呈現(xiàn)極顯著下降,僅為對(duì)照的12.5%。而脫落酸相關(guān)基因與茉莉酸相關(guān)基因的表達(dá)量未出現(xiàn)明顯變化(圖5),說(shuō)明沉默可能會(huì)降低乙烯含量,揭示SlN-like可能參與乙烯介導(dǎo)的抗病毒防御。
統(tǒng)計(jì)分析采用Student’s t檢驗(yàn)(**0.001<P<0.01,***P<0.001),每個(gè)處理進(jìn)行3次生物學(xué)重復(fù),每次生物學(xué)重復(fù)3株番茄,數(shù)值代表3次生物學(xué)重復(fù)的平均值±標(biāo)準(zhǔn)誤The statistical analyses were performed using Student’s t-test (**0.001<P<0.01, ***P<0.001).The experiments were repeated three times with three plants each time.Values represent means±SE from three biological replications。圖6同The same as Fig.6
沉默會(huì)降低乙烯相關(guān)基因的表達(dá),揭示沉默可能影響乙烯合成。為明確乙烯對(duì)表達(dá)的影響,試驗(yàn)以無(wú)菌水為對(duì)照,通過(guò)外施乙烯利(ethephon,ETH),并分別在外施后3、6、12、24 h取樣,提取總RNA,利用實(shí)時(shí)熒光定量PCR檢測(cè)的表達(dá)量。結(jié)果顯示,外施乙烯利后3 h,的表達(dá)與無(wú)菌水處理并無(wú)顯著性差異,而后開(kāi)始上升;外施乙烯利后6 h,的表達(dá)持續(xù)上升,并在12 h達(dá)到最高,是對(duì)照組的2.71倍。之后的表達(dá)開(kāi)始降低,24 h時(shí)恢復(fù)到與對(duì)照組相等水平(圖6),說(shuō)明外施乙烯利會(huì)促進(jìn)的差異表達(dá),進(jìn)一步驗(yàn)證了通過(guò)介導(dǎo)乙烯通路參與抗病毒防御。
圖6 外施乙烯利后SlN-like的表達(dá)
植物病毒嚴(yán)重威脅著作物的產(chǎn)量與品質(zhì)。作物在對(duì)抗病毒過(guò)程中,演化出一系列抵御病毒侵染的機(jī)制,其中包括病原體相關(guān)分子模式觸發(fā)的免疫反應(yīng)(pathogen- associated molecular patterns-triggered immunity,PTI)和效應(yīng)因子觸發(fā)的免疫反應(yīng)(effector-triggered immunity,ETI)。PTI和ETI是植物免疫防御中不可或缺的防御機(jī)制,但ETI防御速度更快、強(qiáng)度更強(qiáng)。TMV是危害最為嚴(yán)重、寄主范圍最廣的植物病毒[21],位列十大植物病毒之首,一旦發(fā)生極難防治[22]。在與植物病毒的長(zhǎng)期協(xié)同進(jìn)化中,某些作物品種進(jìn)化出一些抵御病毒侵染的抗性基因,稱(chēng)為(resistance gene)基因[8]。大部分編碼核苷酸結(jié)合位點(diǎn)-富含亮氨酸重復(fù)結(jié)構(gòu)域(nucleotide binding site and leucine rich repeat domains,NBS-LRR)。NBS-LRR類(lèi)抗病蛋白能夠特異性地識(shí)別病原組分的無(wú)毒蛋白,從而激活效應(yīng)因子觸發(fā)的植物免疫防御反應(yīng)[23]。植物NBS-LRR 蛋白具有針對(duì)細(xì)菌、病毒及真菌病原體“基因?qū)颍╣ene for gene concept)”的抗性,即植物和病原菌中的無(wú)毒基因存在一對(duì)一的關(guān)系,并共同構(gòu)成了一個(gè)全面的病原體檢測(cè)系統(tǒng)[24]。目前已從擬南芥()、水稻()、馬鈴薯等作物中鑒定出多個(gè)NBS-LRR類(lèi)抗性基因,而分離自煙草野生種粘煙草()的便是NBS-LRR類(lèi)抗病基因之一[25-28]。煙草編碼蛋白與TMV解旋酶蛋白p50發(fā)生互作,并通過(guò)識(shí)別p50誘發(fā)HR反應(yīng),造成PCD以限制TMV的進(jìn)一步擴(kuò)張侵染。是植物中鑒定的第一個(gè)TIR-NBS-LRR(toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat)類(lèi)抗病基因,其包含N末端結(jié)構(gòu)域、NB-ARC結(jié)構(gòu)域(APAF-1,disease resistance proteins,CED-4,亦稱(chēng)NBS結(jié)構(gòu)域)及C端的LRR結(jié)構(gòu)域。則是的同源基因,且煙草編碼蛋白含有TIR-NBS-LRR結(jié)構(gòu)域。通過(guò)克隆,并對(duì)其保守結(jié)構(gòu)域進(jìn)行分析,發(fā)現(xiàn)編碼蛋白包含TIR-NBS-NACHT結(jié)構(gòu)域,這與煙草N-like存在差異[12]。研究表明,煙草N-like的TIR-NBS參與TMV p50介導(dǎo)的HR反應(yīng),而LRR并不影響p50依賴(lài)的HR反應(yīng)。SlN-like與煙草N-like僅在TIR-NBS存在相似性,表明SlN-like可能同樣能與p50存在HR反應(yīng)。同樣,本研究表明TMV侵染會(huì)促進(jìn)的表達(dá)(圖2-B),而沉默則促進(jìn)TMV-GFP的侵染(圖4),進(jìn)一步驗(yàn)證了SlN-like可能參與p50的識(shí)別并引起番茄抗病毒防御,但SlN-like與p50的直接識(shí)別證據(jù)仍需進(jìn)一步探索。
乙烯是一種被人們熟知且已經(jīng)被廣泛應(yīng)用于農(nóng)業(yè)的小分子氣體植物激素,是植物三大抗逆激素之一[29-30]。ERF(ethylene-responsive factor)轉(zhuǎn)錄因子家族基因是乙烯信號(hào)傳遞調(diào)控因子EIN3/EIL1的直接作用目標(biāo),其通過(guò)GCC-box直接與乙烯誘導(dǎo)基因啟動(dòng)子的順式作用元件結(jié)合,進(jìn)而調(diào)控植物的生物與非生物脅迫反應(yīng)[31]。多項(xiàng)研究表明乙烯是植物免疫防御的正調(diào)節(jié)因子[32-34]。抗病蛋白R(shí)PW8.1(resistance to powdery mildew 8.1)結(jié)合并穩(wěn)定ACC氧化酶4(acyl-CoA oxidase 4,ACO4),而ERF59能與啟動(dòng)子結(jié)合并抑制其表達(dá),從而反饋抑制RPW8.1介導(dǎo)的細(xì)胞死亡及抗病機(jī)制[35];ERF轉(zhuǎn)錄因子能與病程相關(guān)蛋白(pathogenesis-related protein,PR)啟動(dòng)子結(jié)合,調(diào)控PR蛋白表達(dá),引起抗病防御[36];外源施用乙烯會(huì)誘發(fā)擬南芥植株系統(tǒng)性積累防衛(wèi)素,并提高植物防御素的轉(zhuǎn)錄和翻譯[37]。乙烯對(duì)植物病毒侵染也存在調(diào)控,但研究相對(duì)較少。花椰菜花葉病毒(cauliflower mosaic virus,CaMV)的癥狀產(chǎn)生可能是由于P6與乙烯相關(guān)基因的互作引起[38];NbALD1通過(guò)介導(dǎo)水楊酸和乙烯途徑響應(yīng)蕪菁花葉病毒(turnip mosaic virus,TuMV)侵染[39];乙烯介導(dǎo)植株對(duì)番茄叢矮病毒(tomato bushy stunt virus,TBSV)的極端抗性[40]。本研究表明,沉默后乙烯相關(guān)基因的表達(dá)量降低(圖5),而外施乙烯利后的表達(dá)量升高(圖6),揭示可能通過(guò)影響乙烯含量引起抗病防御。
筆者研究團(tuán)隊(duì)前期研究發(fā)現(xiàn),番茄IP-L(interaction
protein L)、SlHIN1(harpin-induced gene 1)以及SlSYTA(Synaptotagmin A)均可在TMV侵染后高表達(dá),但三者對(duì)病毒侵染的影響不盡相同[20,41-42]。通過(guò)對(duì)番茄抗性基因的挖掘與機(jī)制解析,對(duì)于理解以外殼蛋白互作蛋白IP-L為起點(diǎn),SlHIN1、SlN-like為核心,運(yùn)動(dòng)蛋白互作蛋白SlSYTA為終點(diǎn)的影響病毒侵染的關(guān)系鏈至關(guān)重要,可為番茄的抗性遺傳育種提供理論依據(jù)。
在番茄中克隆并得到具有NBS-LRR結(jié)構(gòu)域的抗病蛋白SlN-like,其表達(dá)受TMV侵染誘導(dǎo),并且作為植物正調(diào)控因子抑制TMV-GFP侵染。沉默降低了的表達(dá),外施乙烯利引起的差異表達(dá),表明SlN-like通過(guò)介導(dǎo)乙烯通路參與抗病毒防御。
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Cloning, Expression and Anti-Virus Function Analysis of
LIU ChangYun1, LI XinYu1, TIAN ShaoRui1, WANG Jing1, PEI YueHong1, MA XiaoZhou1,2, FAN GuangJin1, WANG DaiBin3*, SUN XianChao1*
1College of Plant Protection, Southwest University, Chongqing 400715;2Key Laboratory of Horticulture Science for Southern Mountainous Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715;3Chongqing Tobacco Science Research Institute, Chongqing 400715
【Objective】As an important vegetable crop, tomato () is endangered by various biological factors including pests, fungi, bacteria and viruses.The objective of this study is to clarify the antiviral function and mechanism ofresistance gene, and to provide a theoretical basis for the genetic breeding of antiviraland the targeted development of the antiviral agents.【Method】The full length ofwas obtained from the Solanaceae Genomics Network database and was divided into four segments, fusion PCR was used to amplify the full length of sequence.Bioinformatics was used to analyze the evolutionary relationship, protein characteristics, conserved domains, subcellular location and interaction relationship of SlN-like.real-time fluorescent quantitative PCR was used to analyze theexpression inroots, stems, leaves, flowers and fruits and its response after tobacco mosaic virus (TMV) infection.endogenouswas silenced using tobacco rattle virus (TRV)-mediated gene silencing technology, and the silent plants were inoculated with TMV-GFP to clarify the influence ofon virus infection.The expressions of abscisic acid (ABA), jasmonic acid (JA) and ethylene (ET) hormone-related genes in silenced plants, and the expression ofafter application of ethephon (ETH) for 3, 6, 12 and 24 h were analyzed by real-time fluorescence quantitative PCR to investigate the mechanism of SlN-like regulatory hormone pathway in response to virus infection.【Result】Through molecular cloning and fusion PCR technology, a 3 444 bpwas cloned fromvariety Micro-Tom, and uploaded to NCBI to obtain the sequence number MW792493.Through bioinformatics analysis, it was found that SlN-like contains TIR, NB-ARC and NACHT domains, and is closely related toN-like (AAP44394.1).expressed in all tissues of, with the highest expression in stems, followed by roots, flowers, leaves and fruits.After TMV-GFP infectionat 5th and 7th day, theexpression level was higher than that of PBS treatment, and TMV-GFP infection would cause the expression ofto increase continuously.TRV vector induced silencing ofin, and it was found that silencing 78.3% ofdid not affect tomato growth phenotype, but silencingpromoted the infection of TMV-GFP.Real-time fluorescent quantitative PCR analysis found that the expression of-silent plants was significantly reduced, only 12.5% of that in the control group.The expression ofincreased after 3 h of external application of ethephon, and reached the highest peak at 12 h, which was 2.71 times that of the control group, and returned to normal at 24 h.【Conclusion】SlN-like belongs to the NBS-LRR disease-resistant protein family, its expression is induced by TMV infection.Silencingcan promote TMV-GFP infection and reduce the expression of ethylene-related gene, while external application of ethephon resulted in the differential expression of, revealing that SlN-like participates inantiviral defense through the ethylene pathway.
; SlN-like; tobacco mosaic virus (TMV); gene expression; ethylene
2021-04-02;
2021-04-24
國(guó)家自然科學(xué)基金(31870147,31670148)、西南大學(xué)大學(xué)生創(chuàng)新創(chuàng)業(yè)訓(xùn)練計(jì)劃(X202010635495)、中國(guó)煙草總公司重慶公司科技項(xiàng)目(A20201NY02-1306,B20211-NY1315,B20202NY1338)
劉昌云,E-mail:15228920380@163.com。通信作者孫現(xiàn)超,E-mail:sunxianchao@163.com。通信作者汪代斌,E-mail:467572562@qq.com
(責(zé)任編輯 岳梅)