摘要:【目的】篩選葡萄類胡蘿卜素裂解雙加氧酶(CCD)基因VvCCD1b啟動子互作的轉(zhuǎn)錄因子,挖掘參與調(diào)控葡萄類胡蘿卜素代謝的潛在因子,為深入探究葡萄類胡蘿卜素的代謝調(diào)控網(wǎng)絡(luò)提供理論參考。【方法】克隆VvCCD1b基因的cDNA及其啟動子序列,利用生物信息學(xué)軟件對VvCCD1b基因的染色體位置、啟動子順式作用元件及其編碼蛋白的理化性質(zhì)、保守結(jié)構(gòu)域等進(jìn)行預(yù)測分析。基于轉(zhuǎn)錄組數(shù)據(jù)分析不同葡萄品種及不同處理下葡萄CCD家族成員表達(dá)模式。通過酵母單雜交技術(shù)篩選與VvCCD1b基因啟動子互作的轉(zhuǎn)錄因子,并進(jìn)行點對點驗證?!窘Y(jié)果】通過PCR克隆獲得VvCCD1b基因序列全長1641 bp,位于13號染色體上,編碼546個氨基酸殘基,為親水性蛋白,二級結(jié)構(gòu)由α-螺旋(16.67%)、β-折疊(5.49%)、延伸鏈(24.54%)和無規(guī)則卷曲(53.30%)構(gòu)成,具有RPE65保守結(jié)構(gòu)域。VvCCD1b基因啟動子含有光響應(yīng)元件(G-box、3-AF1 binding site、GATA-motif、TCT-motif)、水楊酸(SA)響應(yīng)元件(SARE)、脫落酸(ABA)響應(yīng)元件(ABRE)及AP2/ERF、WRKY、MADS-box轉(zhuǎn)錄因子結(jié)合元件。VvCCD1b基因表達(dá)水平隨果實發(fā)育逐漸升高且受光照與逆境脅迫的影響。以VvCCD1b基因啟動子為誘餌,初步篩選出VvRAP2-4、VvWRKY4、VvBHLH137轉(zhuǎn)錄因子及葡萄液泡加工酶、葡萄糖苷酶等18個功能蛋白,其中VvRAP2-4、VvWRKY4轉(zhuǎn)錄因子與VvCCD1b基因啟動子間存在互作?!窘Y(jié)論】VvCCD1b為親水性蛋白,基因表達(dá)水平隨果實發(fā)育逐漸升高,且受到干旱、高溫、水澇脅迫和光照的影響。通過酵母單雜交技術(shù)篩選出與VvCCD1b啟動子互作的候選轉(zhuǎn)錄因子。
關(guān)鍵詞:葡萄;VvCCD1b基因;啟動子;酵母單雜交;轉(zhuǎn)錄因子
中圖分類號:S663.103.6文獻(xiàn)標(biāo)志碼:A文章編號:2095-1191(2024)08-2215-10
Cloning of grape VvCCD1b gene and screening of transcription factors interacting with its promoter
CHENYi-heng LI Shao-nan DONG Tian-yu TANG Mei-ling TANG Wen LU Su-wen FANG Jing-gui1*
(1College of Horticulture,Nanjing Agricultural University/Fruit Crop Genetic Improvement and Seedling PropagationEngineering Center of Jiangsu Province,Nanjing,Jiangsu 210095,China;2Yantai Academy of AgriculturalSciences,Yantai,Shandong 265500,China)
Abstract:【Objective】To screen transcription factors that interacted with the promoter of the grape carotenoid clea-vagedixoygenase(CCD)gene VvCCD1b,and explore the potential factors that involved in the regulation of carotenoid metabolism of grape,which provided theoretical reference for further analysis in the metobolic regulation network of grape carotenoid.【Method】The cDNA and promoter sequences of the VvCCD1b gene were cloned.Bioinformatics soft-wares were utilized to predict and analyze the chromosomal location of the VvCCD1b gene,the cis-acting elements of the promoter,as well as the physicochemical properties and conserved domains of its encoded protein.Based on the transcrip-tome data,the expression patterns of grape CCD family members in different grape varieties and under different treatmentswere analyzed.Additionally,yeast one-hybrid technique was employed to screen for transcription factors that interated with the VvCCD1b gene promoter,and the point-to-point validation was performed.【Result】The 1641 bp full-length se-quence of the VvCCD1b gene was obtained through PCR cloning,located on chromosome 13,encoding 546 amino acid residues.It was a hydrophilic protein with a secondary structure composed ofα-helix(16.67%),β-fold(5.49%),extended chain(24.54%)and random coil(53.30%),and contained the RPE65 conserved domain.The VvCCD1b gene promoter contained transcription factors binding elements of light-responsive elements(G-box,3-AF1 binding site,GATA-motif,TCT-motif),salicylic acid(SA)responsive element SARE,and abscisic acid(ABA)responsive elements(ABRE)and AP2/ERF,WRKY,MADS-box.The expression level of the VvCCD1b gene gradually increased with fruit development and was affected by light and adversity stress.In addition,using the VvCCD1b gene promoter as bait,the transcription factors VvRAP2-4,VvWRKY4,VvbHLH137 and 18 functional proteins including grape vacuolar processing enzymes and glucosidases were preliminarily screened,among which the transcription factors VvRAP2-4 and VvWRKY4 interac-ted with the VvCCD1b gene promoter.【Conclusion】VvCCD1b is a hydrophilic protein,the gene expression level gradual-ly increases with the fruit development,and is affected by drought,high temperature,waterlogging stress and light.Can-didate transcription factors interacting with the VvCCD1b promoter are screened by yeast one-hybrid technology.
Key words:grape;VvCCD1b gene;promoter;yeast one-hybrid;transcription factors
Foundation items:National Natural Science Foundation of China(32272647);General Project of China Postdoc-toral Science Foundation(2019M651857);Shandong Key Research and Development(Agricultural Breeding Enginee-ring)Project(2022LZGCQY1018)
0引言
【研究意義】葡萄(Vitis vinifera L.)是我國廣泛栽培的果樹之一,果實營養(yǎng)價值高,具有鮮食、制干、制酒等用途,是我國重要的經(jīng)濟(jì)果品(胡文效和胡舒曼,2022;邵千朔等,2024)。色澤和香氣是葡萄的重要品質(zhì)性狀,不僅影響葡萄果實的市場價值,還影響葡萄酒等加工產(chǎn)品的品質(zhì)(馮帆等,2024)。類胡蘿卜素是一種天然脂溶性色素,廣泛存在于植物果皮、果肉、花、葉和根等部位,其含量對葡萄顏色和香氣的形成至關(guān)重要,也是白葡萄果實的主要呈色物質(zhì)(Rocchi et al.,2016;張克坤,2019;李璽和岳志強,2023)。此外,類胡蘿卜素作為一種次生代謝物,能通過裂解產(chǎn)生植物激素和降異戊二烯類芳香化合物,其中降異戊二烯類芳香化合物具有豐富的花果香味,是組成葡萄和葡萄酒特征香氣的重要物質(zhì)(Sun et al.,2018;Hermannsaetal.,2020;王雅琛等,2021)。類胡蘿卜素裂解雙加氧酶(Carotenoid cleava-gedixoygenase,CCD)是植物類胡蘿卜素代謝途徑的關(guān)鍵酶(Timmins et al.,2020)。因此,開展葡萄CCmQ53ouPBHVA8XI+aYrJiguZjTenuYFlybFhoRgBtpDs=D基因克隆、生物信息學(xué)分析及其上游轉(zhuǎn)錄因子篩選,探究葡萄類胡蘿卜素代謝途徑及葡萄色澤和香氣的形成機理,對提高胡蘿卜素含量和定向培育芳香濃郁的優(yōu)良葡萄果實品種具有重要意義?!厩叭搜芯窟M(jìn)展】CCD是非血紅素鐵依賴性酶家族成員,能以二價鐵離子為輔助因子,在共軛類胡蘿卜素主鏈中相鄰的碳原子之間摻入氧原子,以催化二氧裂解非芳香族雙鍵,產(chǎn)生酮或醛化合物(Dhar et al.,2020)。CCD家族各成員之間因裂解雙鍵的位點、底物和裂解產(chǎn)物種類的不同,在植物體中發(fā)揮著不同的生物學(xué)功能。CCD1能特異性裂解β-類胡蘿卜素、玉米黃質(zhì)和番茄紅素等類胡蘿卜素,從而生成β-紫羅蘭酮、β-環(huán)檸檬醛等降異戊二烯類芳香化合物(張印等,2020);CCD2和CCD4裂解的類胡蘿卜素產(chǎn)物有助于果實顏色與風(fēng)味的形成(Frusciante et al.,2014);CCD7和CCD8參與獨腳金內(nèi)酯的生物合成(Mishra et al.,2017);9-順式-環(huán)氧類胡蘿卜素雙氧合酶(NCED)作為CCD亞家族成員,參與植物激素脫落酸(ABA)的生物合成(Schwartz et al.,2003)。葡萄VvCCD1與擬南芥AtCCD1屬于同源基因,其編碼蛋白能裂解葡萄β-類胡蘿卜素C9′-C10′位點的雙鍵而生成β-紫羅蘭酮;VvCCD4b蛋白的裂解底物和位點與VvCCD1存在差異,但二者均可裂解番茄紅素和ε-胡蘿卜素,VvCCD4b還能裂解ζ-類胡蘿卜素生成香葉基丙酮(Lashbrooke et al.,2013)。CCD家族成員的表達(dá)水平與類胡蘿卜素及其降解產(chǎn)物的積累有關(guān),如草莓成熟過程中葉黃素含量的降低與FaCDD1基因轉(zhuǎn)錄水平的升高存在相關(guān)性(García-Limones et al.,2008);菊花白色和黃色花瓣中大部分類胡蘿卜素代謝通路相關(guān)基因的表達(dá)水平相近,而CmCCD4a基因在類胡蘿卜素含量較低的白色花瓣中表達(dá)量較高,在黃色花瓣中幾乎不表達(dá),暗示菊花花瓣中類胡蘿卜素的積累與CmCCD4a基因的表達(dá)水平呈負(fù)相關(guān)(Yuan et al.,2015);赤霞珠葡萄中VvCCD4b基因的表達(dá)與β-紫羅蘭酮、6-甲基-5-庚烯-2-酮和香葉基丙酮等降異戊二烯化合物的積累呈顯著正相關(guān)(Meng et al.,2020)。有關(guān)CCD家族基因轉(zhuǎn)錄調(diào)控的研究已在多個物種中展開,如通過酵母單雜交篩選出與蘋果CCD7基因啟動子互作的轉(zhuǎn)錄因子BPC 并利用瞬時過表達(dá)試驗發(fā)現(xiàn)BPC1可抑制CCD7基因啟動子的活性(Yue et al.,2015);藏紅花愈傷組織中過表達(dá)CsULT1基因可增強類胡蘿卜素代謝通路關(guān)鍵基因PSY、PDS和BCH的表達(dá),表明CsULT1基因直接或間接參與這些基因的轉(zhuǎn)錄調(diào)控(Ashrafetal.,2015);桂花OfWRKY3和OfERF61能分別結(jié)合OfCCD4基因啟動子中的W-box和CAACA作用元件,以增強OfCCD4基因的表達(dá),進(jìn)而調(diào)節(jié)桂花β-紫羅蘭酮的合成(Han et al.,2016;Han et al.,2019);柑橘CsMADS6能通過結(jié)合基因的啟動子以激活CsPSY、CsCCD1等基因的表達(dá)(Lu et al.,2018);枸杞乙烯響應(yīng)因子LbERF5.1能正向調(diào)控LbCCD4.1基因,從而減少枸杞類胡蘿卜素的積累(Zhao et al.,2023)。【本研究切入點】在葡萄CCD基因轉(zhuǎn)錄調(diào)控的研究中,關(guān)于調(diào)控VvCCD1b基因的轉(zhuǎn)錄因子鮮有報道,且與VvCCD1b上游互作的蛋白尚待挖掘與研究?!緮M解決的關(guān)鍵問題】克隆VvCCD1b基因的cDNA及啟動子序列,利用生物信息學(xué)軟件對VvCCD1b基因的染色體位置、啟動子順式作用元件及其編碼蛋白的理化性質(zhì)、保守結(jié)構(gòu)域等進(jìn)行預(yù)測分析,利用酵母單雜交技術(shù)篩選與VvCCD1b基因啟動子互作的轉(zhuǎn)錄因子,以期為豐富葡萄類胡蘿卜素的代謝調(diào)控網(wǎng)絡(luò)提供理論參考。
1材料與方法
1.1試驗材料
供試葡萄品種為巨峰(V.labrusca×V.vinifera),種植于江蘇省農(nóng)業(yè)科學(xué)院溧水植物科學(xué)基地,采用平棚架栽培模式。選擇5年樹齡的成年結(jié)果樹,于成熟期采集無病蟲害且大小一致的葡萄果實,液氮速凍后置于-80℃冰箱保存。葡萄cDNA文庫、試驗載體來自南京農(nóng)業(yè)大學(xué)園藝學(xué)院葡萄遺傳育種與基因組學(xué)實驗室。大腸桿菌DH5α感受態(tài)細(xì)胞、農(nóng)桿菌感受態(tài)細(xì)胞(GV3101)購自北京擎科生物科技股份有限公司;酵母感受態(tài)細(xì)胞、Carrier DNA和LiAC/PEG購自上海唯地生物技術(shù)有限公司;限制性內(nèi)切酶、YPD Plus復(fù)蘇培養(yǎng)基購自北京寶日醫(yī)生物技術(shù)有限公司;多糖多酚植物DNA提取試劑盒、金擔(dān)子素A(AbA)購自上海翊圣生物科技股份有限公司;瓊脂粉、氯化鈉、無水葡萄糖、酵母提取物、胰蛋白胨購自南京壽德生物科技有限公司;同源重組試劑盒購自北京金沙生物科技有限公司;MatchmakerTM Insert Check PCR MixⅠ試劑盒購自美國Clontech公司;酵母質(zhì)粒小提試劑盒購自武漢普因特生物工程有限公司;腺嘌呤(Ade)購自上海麥克林生化科技股份有限公司;無氨基酸酵母氮源(YNB)、酵母缺陷型培養(yǎng)基(SD/-Ura、SD/-Leu)購自北京酷來搏科技有限公司。
1.2試驗方法
1.2.1 VvCCD1b基因及共啟動子序列克隆采用張孟偉(2021)改良的CTAB法提取RNA,通過反轉(zhuǎn)錄試劑盒反轉(zhuǎn)錄合成cDNA第一鏈。使用多糖多酚植物DNA提取試劑盒提取巨峰葡萄果皮DNA。通過Ensembl數(shù)據(jù)庫下載葡萄VvCCD1b基因編碼區(qū)(CDS)序列和啟動子序列(1380 bp),據(jù)此設(shè)計引物VvCCD1b-F:5'-ATGCCGAAGAAGATGGCGGAGAA-3',VvCCD1b-R:5'-AAGTTTTGCTTGTTCTTTGAGTTG C-3';pro-VvCCD1b-F:5'-TCGTGGTGCCAAGGTTA G-3',proVvCCD1b-R:5'-TGGAGC-TTTTATCACCTC CTC-3'。分別以巨峰葡萄cDNA和DNA為模板,PCR克隆得到VvCCD1b基因的CDS和啟動子序列(pro-VvCCD1b)后進(jìn)行測序。
1.2.2生物信息學(xué)分析分別使用ExPASy(https://web.expasy.org/protparam/)網(wǎng)站預(yù)測VvCCD1b蛋白的理化性質(zhì),PRABI(http://www.prabi.fr/)網(wǎng)站預(yù)測蛋白的二級結(jié)構(gòu),SWISS-MODEL(https://swissmo-del.expasy.org/interactive)網(wǎng)站構(gòu)建蛋白的三級結(jié)構(gòu)模型,Ensembl(http://plants.ensembl.org/)數(shù)據(jù)庫查找基因所在的染色體位置,MG2C(http://mg2c.iask.in/mg2c_v2.0/)繪制染色體定位圖,PlantCARE(http://bioinformatics.psb.ugent.be/webtools/plantcare/html/)和Softberry(http://linux1.softberry.com/)網(wǎng)站分析啟動子的順式作用元件,TBtools進(jìn)行可視化分析,SMART(http://smart.embl-heidelberg.de/)網(wǎng)站預(yù)測蛋白的保守結(jié)構(gòu)域。從NCBI(https://www.ncbi.nlm.nih.gov/)數(shù)據(jù)庫下載不同葡萄品種及不同處理下的轉(zhuǎn)錄組數(shù)據(jù),包括夏黑葡萄不同時期果實發(fā)育(GSE77218)、水澇脅迫(SRP070475)、干旱脅迫(SRP074162);巨峰葡萄高溫脅迫(PRJNA752263);赤霞珠葡萄轉(zhuǎn)色期摘葉處理(GSE157347)。利用TBtools繪制葡萄CCD家族成員基因表達(dá)熱圖。
1.2.3誘餌載體菌株構(gòu)建將VvCCD1b基因啟動子序列連接至pAbAi載體,得到重組質(zhì)粒pAbAi-proVvCCD1b。使用BstBⅠ限制性內(nèi)切酶對pAbAi-proVvCCD1b進(jìn)行酶切,經(jīng)過1.2%瓊脂糖凝膠電泳檢測后回收純化酶切產(chǎn)物。將酶切后的重組質(zhì)粒轉(zhuǎn)化酵母感受態(tài)細(xì)胞,并涂布于SD/-Ura酵母培養(yǎng)基,28℃培養(yǎng)3 d,待長出酵母單菌落后,使用Match-makerTM Insert Check PCR MixⅠ試劑盒進(jìn)行PCR鑒定,得到陽性誘餌載體菌株。
1.2.4誘餌載體自激活檢測將含誘餌載體的酵母單菌落挑至0.9%的生理鹽水中,將菌液OD600 nm調(diào)至0.00 吸取100μL稀釋后的菌液,依次涂布到含有不同濃度(0、10、25、40、50 ng/mL)AbA的SD/-Ura酵母培養(yǎng)基中,28℃培養(yǎng)3~4 d,觀察不同濃度AbA培養(yǎng)基中酵母的生長情況,篩選出抑制酵母自激活的最適AbA濃度。
1.2.5酵母單雜交文庫篩選將cDNA文庫轉(zhuǎn)化含有誘餌載體的酵母感受態(tài)細(xì)胞中,涂布于30個SD/-Leu/AbA酵母培養(yǎng)基中。28℃培養(yǎng)3~4 d,挑取生長狀態(tài)良好的酵母單菌落,劃線至SD/-Leu/AbA固體培養(yǎng)基上,初步去除假陽性克隆菌株。挑取正常生長的菌落進(jìn)行菌液PCR鑒定,1.2%瓊脂糖凝膠電泳檢測后將鑒定正確的菌株送往通用生物(安徽)股份有限公司測序,測序引物為pGADT7通用引物(F:5'-TAATACGACTCACTATAGGGC-3',R:5'-AGAT GGTGCACGATGCACAG-3')。測序結(jié)果通過NCBI數(shù)據(jù)庫進(jìn)行BLAST比對分析,以獲取序列的名稱、登錄號及完整的CDS序列。
1.2.6點對點驗證將待驗證的酵母單菌落挑至4 mL YPDA培養(yǎng)基中,28℃190 r/min培養(yǎng)至菌液渾濁。使用酵母質(zhì)粒小提試劑盒提取質(zhì)粒并轉(zhuǎn)化DH5α感受態(tài)細(xì)胞,通過菌液擴大培養(yǎng)及質(zhì)粒提取獲得高濃度質(zhì)粒。分別將其與pGADT7空載質(zhì)粒轉(zhuǎn)化含有誘餌載體的酵母感受態(tài)細(xì)胞,并涂布至SD/-Leu和SD/-Leu/AbA酵母培養(yǎng)基中,待單菌落長大,挑取單克隆打點在SD/-Leu/AbA固體培養(yǎng)基上,稀釋倍數(shù)分別為10-1、10-2和10-3,28℃培養(yǎng)3~4 d,觀察菌落的生長情況。
2結(jié)果與分析
2.1 VvCCD1b基因克隆及生物信息學(xué)分析結(jié)果
通過PCR擴增得到VvCCD1b基因CDS序列長1641 bp(圖1)。TBtools可視化VvCCD1b基因的染色體位置,發(fā)現(xiàn)該基因位于13號染色體上(圖2)。通過生物信息學(xué)在線網(wǎng)站分析發(fā)現(xiàn),VvCCD1b基因編碼546個氨基酸殘基,蛋白分子量為61634.87 Da,理論等電點(pI)為6.13,屬于親水性蛋白;該蛋白二級結(jié)構(gòu)由α-螺旋(16.67%)、β-折疊(5.49%)、無規(guī)則卷曲(53.30%)和延伸鏈(24.54%)組成(圖3-A)。SWISS-MODEL構(gòu)建的VvCCD1b三級結(jié)構(gòu)模型如圖3-B所示。SMART預(yù)測結(jié)果顯示,VvCCD1b蛋白具有RPE65保守結(jié)構(gòu)域(圖4)。
2.2 VvCCD1b基因啟動子序列克隆及順式作用元件分析結(jié)果
通過PCR擴增得到VvCCD1b基因上游啟動子序列長1380bp(圖5-A)。在線網(wǎng)站分析順式作用元件發(fā)現(xiàn),該序列包含4個光響應(yīng)元件(G-box、3-AF1binding site、GATA-motif和TCT-motif)、1個水楊酸(SA)響應(yīng)元件(SARE)、1個ABA響應(yīng)元件(ABRE)、2個MADS-box轉(zhuǎn)錄因子結(jié)合元件(CArG-box)、1個AP2/ERF轉(zhuǎn)錄因子結(jié)合元件(GCC-box)和1個WRKY轉(zhuǎn)錄因子結(jié)合元件(W-box)(圖5-B),表明VvCCD1b基因表達(dá)可能受光照、ABA和SA的影響,MADS-box、AP2/ERF和WRKY家族的轉(zhuǎn)錄因子也可能對VvCCD1b基因存在調(diào)控作用。
2.3葡萄CCD家族成員表達(dá)模式分析結(jié)果
對夏黑葡萄不同發(fā)育時期的轉(zhuǎn)錄組數(shù)據(jù)分析發(fā)現(xiàn),CCD家族成員中VvCCD1b基因的表達(dá)水平最高,從綠果期至成熟期的表達(dá)水平整體呈上升趨勢(圖6-A)。為了探究不同非生物脅迫對VvCCD1b基因表達(dá)水平的影響,分析夏黑葡萄在干旱脅迫和水澇脅迫的轉(zhuǎn)錄組數(shù)據(jù),結(jié)果發(fā)現(xiàn)干旱和水澇脅迫導(dǎo)致VvCCD1b基因的表達(dá)水平升高(圖6-B和圖6-C)。通過分析巨峰葡萄高溫脅迫的轉(zhuǎn)錄組數(shù)據(jù)發(fā)現(xiàn),47℃處理4h后VvCCD1b基因的表達(dá)水平升高(圖6-D)。VvCCD1b基因的啟動子序列中含有較多的光響應(yīng)元件,通過分析轉(zhuǎn)錄組數(shù)據(jù)發(fā)現(xiàn),赤霞珠葡萄轉(zhuǎn)色期進(jìn)行摘葉處理可提高成熟果實中VvCCD1b基因的表達(dá)水平(圖6-E),且摘葉處理還可改善葡萄果實的光照條件,表明VvCCD1b基因表達(dá)水平可能與光照有關(guān)。
2.4 VvCCD1b基因誘餌載體菌株構(gòu)建結(jié)果
將酶切后的pAbAi載體與VvCCD1b基因啟動子片段進(jìn)行同源重組,并通過PCR和瓊脂糖凝膠電泳檢測出與啟動子片段長度一致的條帶(圖7-A),說明成功構(gòu)建誘餌載體pAbAi-proVvCCD1b。將誘餌載體pAbAi-proVvCCD1b進(jìn)行單酶切線性化(圖7-B),并轉(zhuǎn)化酵母感受態(tài)細(xì)胞。由圖7-C可知,酵母菌在SD/-Ura培養(yǎng)基上生長狀態(tài)良好,表明誘餌載體酵母菌株構(gòu)建成功。
2.5誘餌載體自激活檢測結(jié)果
誘餌載體自激活通常會導(dǎo)致篩選調(diào)控蛋白的過程中出現(xiàn)過多的假陽性克隆。將含有pAbAi-proVvCCD1b的酵母菌分別涂布于不同濃度AbA的SD/-Ura培養(yǎng)基中,結(jié)果如圖8所示。50 ng/mL的AbA能最大程度抑制含有pAbAi-proVvCCD1b的酵母菌自激活。
2.6酵母單雜交文庫篩選結(jié)果
將cDNA文庫轉(zhuǎn)化含有pAbAi-proVvCCD1b的酵母感受態(tài)細(xì)胞中,涂布于30個SD/-Leu/AbA50培養(yǎng)基中進(jìn)行酵母單雜交文庫篩選。由圖9-A可知,共生長出72個單菌落,將單菌落劃線至SD/-Leu/AbA50培養(yǎng)基中生長3 d進(jìn)行初步篩選。利用pGADT7引物從劃線平板中選取生長狀態(tài)良好的酵母菌進(jìn)行菌液PCR鑒定,結(jié)果如圖9-B所示。將測序結(jié)果在NCBI數(shù)據(jù)庫中進(jìn)行BLAST比對,初步篩選出與VvCCD1b基因啟動子互作的VvRAP2-4、VvWRKY4、VvBHLH137轉(zhuǎn)錄因子和葡萄液泡加工酶、葡萄糖苷酶等18個功能蛋白(表1)。
2.7酵母互作點對點驗證
為篩選VvCCD1b基因的轉(zhuǎn)錄調(diào)控因子,提取注釋信息為VvWRKY4、VvBHLH137和VvRAP2-4陽性克隆的酵母質(zhì)粒,轉(zhuǎn)化大腸桿菌感受態(tài)細(xì)胞,經(jīng)擴大培養(yǎng)和質(zhì)粒提取得到高濃度質(zhì)粒,將高濃度質(zhì)粒轉(zhuǎn)化含pAbAi-proVvCCD1b的酵母感受態(tài)細(xì)胞中,以pGADT7空載質(zhì)粒為陰性對照,分別涂布于SD/-Leu/AbA0和SD/-Leu/AbA50固體培養(yǎng)基上,結(jié)果(圖10)發(fā)現(xiàn)酵母在SD/-Leu培養(yǎng)基上生長良好,表明質(zhì)粒成功轉(zhuǎn)入酵母感受態(tài)細(xì)胞。在SD/-Leu/AbA50培養(yǎng)基中,轉(zhuǎn)化pGADT7-VvBHLH137和pGADT7質(zhì)粒的酵母感受態(tài)細(xì)胞不能生長,轉(zhuǎn)化pGADT7-VvRAP2-4和pGADT7-VvWRKY4質(zhì)粒的酵母感受態(tài)細(xì)胞能正常生長。為了進(jìn)一步驗證互作關(guān)系,將稀釋倍數(shù)為10-1、10-2和10-3的酵母感受態(tài)細(xì)胞點板于SD/-Leu/AbA50培養(yǎng)基中,轉(zhuǎn)化pGADT7-VvRAP2-4和pGADT7-VvWRKY4質(zhì)粒的酵母感受態(tài)細(xì)胞在不同的稀釋倍數(shù)下均能正常生長,轉(zhuǎn)化pGADT7-VvBHL137質(zhì)粒的酵母感受態(tài)細(xì)胞不能正常生長,轉(zhuǎn)化pGADT7的酵母感受態(tài)細(xì)胞在10-1稀釋倍數(shù)下能微弱生長,在10-2和10-3稀釋倍數(shù)下不能正常生長。上述結(jié)果表明,轉(zhuǎn)錄因子VvRAP2-4和VvWRKY4與VvCCD1b基因的啟動子存在互作。
3討論
本研究克隆得到葡萄CCD基因VvCCD1b,編碼546個氨基酸殘基,與石榴PgCCD1b(劉盛雨等,2018)和杏PaCCD1(付鴻博等,2024)均為親水性蛋白;該蛋白二級結(jié)構(gòu)中各組分占比排序為無規(guī)則卷曲>延伸鏈>α-螺旋>β-折疊,與梨CCD蛋白(胡盼盼和付鴻博,2023)的研究結(jié)果一致。VvCCD1b蛋白含有RPE65保守結(jié)構(gòu)域,該結(jié)構(gòu)域包含多個組氨酸活性位點,是CCD蛋白行使功能的主要區(qū)域(Polia-kovetal.,2005)。已有研究表明,葡萄類胡蘿卜素含量隨果實發(fā)育成熟呈下降趨勢(張禎,2022)。本研究通過VvCCD1b基因啟動子順式作用元件分析發(fā)現(xiàn),VvCCD1b基因包含較多的光響應(yīng)元件和激素響應(yīng)元件;轉(zhuǎn)錄組數(shù)據(jù)分析發(fā)現(xiàn),VvCCD1b基因從綠果期至成熟期的表達(dá)水平呈升高趨勢,推測VvCCD1b基因轉(zhuǎn)錄水平與葡萄類胡蘿卜素的變化存在相關(guān)性。ABA和SA等激素信號分子在植物抵御干旱和水澇脅迫中發(fā)揮重要作用(孫彤彤,2019;項洪濤等,2022;郗慧茹等,2023)。通過轉(zhuǎn)錄組數(shù)據(jù)分析發(fā)現(xiàn),葡萄在干旱和水澇脅迫下VvCCD1b基因表達(dá)水平升高,可能與該基因啟動子中含有的ABA和SA響應(yīng)元件有關(guān)。研究發(fā)現(xiàn),葡萄β-大馬士酮等降異戊二烯類物質(zhì)的積累與降水和濕度有關(guān),葡萄CCD家族成員基因的表達(dá)也受水分的影響(Xu et al.,2015;Savoietal.,2016)。
乙烯響應(yīng)因子RAP2-4屬于AP2/ERF家族成員,該家族在調(diào)節(jié)植物生長發(fā)育、激素信號轉(zhuǎn)導(dǎo)及生物和非生物脅迫反應(yīng)中發(fā)揮重要作用(Feng et al.,2005)。研究表明,擬南芥AtRAP2-4能激活β-酮脂酰-CoA合成酶基因AtKCS2和烷烴合成酶基因AtCER1的表達(dá),有利于干旱脅迫下擬南芥蠟質(zhì)層的生物合成(Yang et al.,2020)。過表達(dá)AtRAP2-4基因還能導(dǎo)致擬南芥葉綠素降解加快和衰老相關(guān)基因表達(dá)水平升高(Xu etal.,2010)。WRKY轉(zhuǎn)錄因子主要參與調(diào)控植物的生長發(fā)育及響應(yīng)生物和非生物脅迫的過程(Lai et al.,2008)。在鹽脅迫和茉莉酸甲酯(MeJA)脅迫下,擬南芥AtWRKY3和AtWRKY4基因表達(dá)水平顯著升高,敲除AtWRKY3和AtWRKY4突變體植株的根系生長則受顯著抑制(Li etal.,2021)。Liang和Jiang(2017)通過鹽脅迫處理巴氏杜氏藻發(fā)現(xiàn),部分含有W-box結(jié)合位點的類胡蘿卜素代謝基因和4個WRKY轉(zhuǎn)錄因子基因的表達(dá)水平升高,表明巴氏杜氏藻可能通過WRKY轉(zhuǎn)錄因子調(diào)控類胡蘿卜素含量以適應(yīng)鹽脅迫環(huán)境,且WRKY轉(zhuǎn)錄因子已被證明受到SA、茉莉酸(JA)和ABA等多種信號物質(zhì)的誘導(dǎo)(Li etal.,2021)。OsWRKY4作為重要的正調(diào)節(jié)因子,能通過JA依賴性信號通路參與水稻紋枯病的防御反應(yīng)(Wang et al.,2015)。吳淼(2017)使用SA、JA和ABA處理桂花后發(fā)現(xiàn)OfWRKY3和OfCCD4基因的表達(dá)水平基本一致,通過煙草轉(zhuǎn)化試驗證明OfWRKY3能促進(jìn)OfCCD4基因的表達(dá)。本研究結(jié)合啟動子順式作用元件和轉(zhuǎn)錄組數(shù)據(jù)分析發(fā)現(xiàn),VvCCD1b含有SA和ABA響應(yīng)元件且表達(dá)水平受干旱、水澇和高溫脅迫的影響。但葡萄VvRAP2-4和VvWRKY4能否在激素介導(dǎo)或逆境脅迫條件下調(diào)控VvCCD1b基因的表達(dá),仍需進(jìn)一步探索。
4結(jié)論
VvCCD1b為親水性蛋白,基因表達(dá)水平隨果實發(fā)育逐漸升高,且受到干旱、高溫、水澇脅迫和光照的影響。通過酵母單雜交技術(shù)篩選出與VvCCD1b啟動子互作的候選轉(zhuǎn)錄因子。在激素響應(yīng)、逆境脅迫條件下候選蛋白對VvCCD1b表達(dá)的轉(zhuǎn)錄調(diào)控機制將是后續(xù)重點研究方向。
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