黃桂媛 張瑛 林玲 韓佳宇 時(shí)曉芳 曹雄軍 郭榮榮
摘要:【目的】利用酵母單雜交文庫篩選巨峰葡萄VvFT基因啟動子上游調(diào)控因子,挖掘參與調(diào)控葡萄開花時(shí)間的因子,為揭示花期轉(zhuǎn)變代謝通路和定向改良葡萄品種提供理論參考。【方法】利用PlantCARE分析預(yù)測VvFT基因啟動子順式作用元件,并以VvFT基因啟動子為誘餌,利用酵母單雜交文庫篩選技術(shù),篩選作用在VvFT基因啟動子上游的調(diào)控因子。【結(jié)果】葡萄VvFT基因啟動子區(qū)域存在13種啟動子順式作用元件,包括A-box、CAAT-box和TATA-box組成型調(diào)控元件;光響應(yīng)調(diào)控元件ATC-motif、Box 4、G-Box和GT1-motif;茉莉酸甲酯(MeJA)響應(yīng)調(diào)控元件CGTCA-motif和TGACG-motif;干旱誘導(dǎo)的MYB結(jié)合位點(diǎn)元件MBS;玉米蛋白代謝必需的調(diào)控元件O2-site;參與生物鐘控制的調(diào)控元件circadian;厭氧誘導(dǎo)必需調(diào)控元件ARE。以VvFT基因啟動子為誘餌,篩選獲得34條表達(dá)序列標(biāo)簽(EST),其中有21條為未知功能,有13條在植物生長、抗逆防御、信號轉(zhuǎn)導(dǎo)、轉(zhuǎn)錄調(diào)控、蛋白酶等方面均有已知或預(yù)測的功能,包括轉(zhuǎn)錄抑制因子ft41、GRF1互作因子ft44、NAP1相關(guān)蛋白ft64及ft70分子伴侶DnaJ10。酵母單雜交點(diǎn)對點(diǎn)驗(yàn)證結(jié)果表明VvDnaJ10和VvFT基因啟動子之間有相互作用。【結(jié)論】通過酵母單雜交文庫篩選獲取13條候選EST,雖然大部分EST功能預(yù)測分析結(jié)果與VvFT調(diào)控開花時(shí)間無明顯的直接關(guān)系,但研究結(jié)果為進(jìn)一步探索VvFT轉(zhuǎn)錄或表達(dá)水平控制葡萄開花時(shí)間的分子機(jī)制提供侯選基因。
關(guān)鍵詞: 葡萄;VvFT基因;啟動子;酵母單雜交文庫;調(diào)控因子;篩選
中圖分類號: S663.1? ? ? ? ? ? ? ? ? ? ? ? ?文獻(xiàn)標(biāo)志碼: A 文章編號:2095-1191(2020)12-2875-09
Abstract:【Objective】Screening of upstream regulatory factors of VvFT gene promoter in kyoho grape by yeast one-hybrid library and exploring factors that involved in the regulation of flowering time of grape could help to reveal the me-tabolic pathway during flowering and provide a theoretical basis for the directional improvement of grape varieties. 【Me-thod】Potential cis-acting regulatory elements of the VvFT promoter were analyzed online in PlantCARE database. VvFT promoter sequence was used as a bait to search potential regulatory factors acting on VvFT promoter upstream by yeast one-hybrid library screening system in latent buds. 【Result】There were 13 cis-acting elements in the VvFT promoter region of kyoho grape, including constitutive regulatory elements(A-box, CAAT-box and TATA-box), light responsive elements(ATC-motif, Box 4, G-box and GT1-motif), cis-acting regulatory elements involved in the MeJA-responsiveness(CGTCA-motif and TGACG-motif), MYB binding site involved in drought-inducibility, cis-acting regulatory element involved in zein metabolism regulation(O2-site), cis-acting regulatory element involved in circadian control(circadian) and cis-acting regulatory element essential for the anaerobic induction(ARE). Using VvFT promoter as a bait,a total of 34 ESTs were acquired in the yeast one-hybrid library. Functional classification results showed that 21 were unknown functional proteins,and 13 had known or predicted functions including plant growth, stress resistance, signal transduction, transcriptional regulation, proteases. Among them,there were transcriptional suppressor ft41,GRF1 interaction factor ft44, NAP1-related protein ft64 and ft70 molecular chaperone DnaJ10. The results of yeast single hybridization point to point verification showed that there was interaction between VvDnaJ10 and VvFT promoter. 【Conclusion】In this study,13 candidate ESTs are obtained by yeast one-hybrid library screening system. Although most of the results of ESTs function prediction analysis have no obvious direct relationship with VvFT regulating flowering time,? the results provide candidate gene resources for further exploration of the molecular mechanism of VvFT transcription or expression level controlling flowering time in grape.
Key words: grape; VvFT gene; promoter; yeast one-hybrid library; regulator; screening
Foundation item: Guangxi Natural Science Foundation(2017GXNSFBA198100,2020GXNSFBA297006);Key Research and Development Plan Project of Guangxi(Guike AB18126005); Basic Research Project of Guangxi Academy of Agricultural Sciences(Guinongke 2021YT127)
0 引言
【研究意義】光周期、春化、環(huán)境溫度、植物激素和自主開花通路相互關(guān)聯(lián)并協(xié)調(diào)開花時(shí)間,以提高植物適應(yīng)性和繁殖率(Wickland and Hanzawa,2015) 。自主開花通路下游有2個(gè)重要基因,分別為FT(FLOWERING LOCUS T)和TFL1(TERMINAL FLOWER 1),其編碼1對與磷脂酰乙醇胺結(jié)合蛋白(PEBP)高度同源性的開花調(diào)節(jié)因子(Wickland and Hanzawa,2015),控制植物開花時(shí)間。葡萄(Vitis vinifera L.)是世界上廣泛種植的果樹之一,我國的鮮食葡萄產(chǎn)量占全球葡萄產(chǎn)量的14%(高世敏等,2018)。挖掘參與葡萄開花時(shí)間調(diào)控因子,如參與溫度、激素和調(diào)節(jié)自主開花等響應(yīng)因子,揭示開花時(shí)間調(diào)控代謝通路,有助于定向改良葡萄品種,優(yōu)化葡萄植株?duì)I養(yǎng)生長與生殖生長的時(shí)空關(guān)系,以實(shí)現(xiàn)葡萄高產(chǎn)優(yōu)產(chǎn)的目的?!厩叭搜芯窟M(jìn)展】莖頂端分生組織向花分生組織的分化是有花植物的一個(gè)關(guān)鍵發(fā)育過程?;ㄆ谵D(zhuǎn)變主要通過整合環(huán)境和內(nèi)源性刺激來調(diào)節(jié),從而形成一個(gè)復(fù)雜的分級信號網(wǎng)絡(luò)。FT蛋白是其中的一個(gè)重要移動信號,也是成花素的主要成分,在介導(dǎo)開花過程中發(fā)揮核心作用,其編碼基因轉(zhuǎn)錄受正調(diào)控因子和負(fù)調(diào)控因子調(diào)控。葉片維管組織中轉(zhuǎn)錄調(diào)控因子CO(CONSTANS)與FT基因啟動子近端區(qū)域的一個(gè)獨(dú)特的順式元件結(jié)合并激活FT基因轉(zhuǎn)錄,有效地促進(jìn)花期的轉(zhuǎn)變(An et al.,2004;Tiwari et al.,2010)。除光周期外,環(huán)境因素也調(diào)節(jié)FT基因表達(dá)。針對FT基因啟動子或非編碼區(qū)域的溫度響應(yīng)型FT調(diào)節(jié)因子FLC(FLOWERING LOCUS C)與SVP(SHORT VEGETATIVE PHASE)形成MADS-box蛋白復(fù)合物,并直接與第一個(gè)內(nèi)含子和FT啟動子區(qū)域的CArG位點(diǎn)結(jié)合來抑制FT基因轉(zhuǎn)錄(Searle et al.,2006;Lee et al.,2007;Li et al.,2008)。與大多數(shù)參與發(fā)育機(jī)制的基因轉(zhuǎn)錄本一樣,F(xiàn)T基因mRNA也會迅速降解(Seo et al.,2011)。但近年研究表明,F(xiàn)T基因mRNA是由WER(WEREWOLF)的間接作用穩(wěn)定下來,而WER是只存在于表皮組織的蛋白復(fù)合物的一部分(Seo et al.,2011)。此外,已有較多FT基因互作蛋白的相關(guān)研究報(bào)道(Liu et al.,2012)。如編碼分子伴侶DnaJ蛋白的J3基因能調(diào)控?cái)M南芥提前開花(Shen et al.,2011),說明DnaJ蛋白對FT基因功能具有潛在調(diào)節(jié)作用;蘋果中VOZ1(Vascular plant one zinc finger protein 1)和TCP(TEOSINTE BRANCHED 1,CYCLOIDEA and PROLIFERATING CELL FACTORs)蛋白均與FT蛋白相互作用控制葉片和果實(shí)的發(fā)育(Mimida et al.,2011)?!颈狙芯壳腥朦c(diǎn)】FT基因的功能在蛋白水平上的調(diào)控機(jī)制鮮有報(bào)道,更多的FT互作蛋白有待被挖掘與研究。與研究葡萄FT基因(VvFT)功能相比,對VvFT基因啟動子區(qū)域潛在的調(diào)控因子挖掘,更有利于從轉(zhuǎn)錄水平了解該基因?qū)ζ咸验_花時(shí)間的調(diào)控機(jī)理,但目前鮮見相關(guān)報(bào)道?!緮M解決的關(guān)鍵問題】利用PlantCARE預(yù)測VvFT基因啟動子順式作用元件,并以VvFT基因啟動子為誘餌,利用酵母單雜交文庫篩選技術(shù)篩選作用于VvFT基因啟動子上游的調(diào)控因子,挖掘潛在參與調(diào)控葡萄開花時(shí)間的因子,為揭示VvFT基因?qū)ㄆ诘恼{(diào)控機(jī)制、花期轉(zhuǎn)變代謝通路和定向改良葡萄品種提供理論參考。
1 材料與方法
1. 1 試驗(yàn)材料
供試葡萄品種為6年生巨峰葡萄(V. labrusca×V. vinifera‘Kyoho),種植于廣西農(nóng)業(yè)科學(xué)院五十畝雙季葡萄栽培示范基地,采用簡易避雨雙十字V型架栽培模式,栽植密度為2.0 m×3.3 m,樹勢中等,管理水平良好。采集巨峰葡萄一季果冬芽,用于VvFT基因啟動子克隆、酵母單雜交文庫構(gòu)建和VvDnaJ10基因克隆。高效植物基因組DNA提取試劑盒購自天根生化科技(北京)有限公司。T4 DNA連接酶,Taq DNA聚合酶、SD/-Ura DO Supplement、SD/Leu DO Supplement、金擔(dān)子素A(AbA)、Matchmaker Insert Check PCR Mix 1、CHROMA SPIN TE-400層析柱和Make Your Own “Mate & Plate” Library System試劑盒均購自Clontech公司;腺嘌呤硫酸鹽[Adenine Sulfate(Ade)]購自Amresco公司;限制性內(nèi)切酶和凝膠回收試劑盒均購自Fermentas公司。
1. 2 試驗(yàn)方法
1. 2. 1 VvFT啟動子克隆及序列分析 以歐洲葡萄黑比諾中FT基因上游1500 bp左右的序列設(shè)計(jì)引物pFT-F:5'-CGGGGTACCATGAGTTTTTTTATTTAT TGTTATCTCATA-3'(下劃線為Kpn I酶切位點(diǎn))和pFT-R:5'-CCCAAGCTTAGCTATCCAAACTGTATT GATCTATGGATT-3'(下劃線為Hind III酶切位點(diǎn))。使用高效植物基因組DNA提取試劑盒提取巨峰葡萄冬芽總DNA。以巨峰葡萄冬芽總DNA為模板,PCR擴(kuò)增VvFT基因啟動子序列(pVvFT),PCR反應(yīng)體系25.0 μL:Premix TaqTM 12.5 μL,10 μmol/L引物pFT-F和pFT-R各1.0 μL,50 ng/μL DNA模板1.0 μL,ddH2O補(bǔ)足至25.0 μL。擴(kuò)增程序:94 ℃ 3 min;94 ℃ 30 s,55 ℃ 30 s,72 ℃ 1 min 30 s,進(jìn)行33個(gè)循環(huán);72 ℃ 10 min。將擴(kuò)增的目的片段連接至pMD18-T載體上,獲得重組質(zhì)粒pMD18-T-pVvFT,送至北京六合華大基因科技股份有限公司測序。利用PlantCARE對VvFT基因啟動子序列進(jìn)行順式調(diào)控元件預(yù)測分析。
1. 2. 2 誘餌載體pAbAi-pVvFT構(gòu)建 用限制性內(nèi)切酶Kpn I和Hind III對測序正確的重組質(zhì)粒pMD18-T-pVvFT和pAbAi載體進(jìn)行雙酶切,回收目的片段并進(jìn)行連接,獲得誘餌載體pAbAi-pVvFT,轉(zhuǎn)化大腸桿菌TOP10感受態(tài)細(xì)胞,取150 μL菌液涂布于含30 ng/mL氨芐青霉素的LB固體培養(yǎng)基上,37 ℃過夜培養(yǎng)。提取陽性克隆單菌落的重組質(zhì)粒pAbAi-pVvFT進(jìn)行雙酶切鑒定,并送至北京六合華大基因科技股份有限公司測序鑒定。
1. 2. 3 誘餌載體pAbAi-pVvFT轉(zhuǎn)化酵母菌株 分別將限制性內(nèi)切酶Bstb I線性化的誘餌載體pAbAi-pVvFT和陽性對照質(zhì)粒pAbAi-p53轉(zhuǎn)化Y1HGold酵母感受態(tài)細(xì)胞,并各取150 μL菌液涂布于SD/-Ura和SD/-Ura/AbA(500 ng/mL)培養(yǎng)基上,30 ℃培養(yǎng)3 d。挑取SD/-Ura培養(yǎng)基上的單菌落,利用Matchmaker Insert Check PCR Mix 1進(jìn)行菌落PCR鑒定。分別挑取含誘餌載體pAbAi-pVvFT和陽性對照pAbAi-p53的陽性單菌落,在SD/-Ura/AbA(500 ng/mL)培養(yǎng)基上劃線培養(yǎng)3 d,獲得Y1H-pAbAi-pVvFT和Y1H-pAbAi-p53酵母菌株。
1. 2. 4 cDNA文庫構(gòu)建 參照TRIzol試劑盒說明提取冬芽總RNA,采用Oligotex mRNA試劑盒分離純化mRNA。以mRNA為模板,經(jīng)SMART逆轉(zhuǎn)錄合成cDNA第一鏈,利用長距離PCR(LD-PCR)擴(kuò)增技術(shù)合成雙鏈cDNA,并用1%瓊脂糖凝膠電泳進(jìn)行檢測,最后用CHROMA SPIN TE-400層析柱進(jìn)行純化,參照Make Your Own “Mate & Plate”Library System試劑盒使用說明構(gòu)建葡萄冬芽cDNA文庫。
1. 2. 5 VvFT基因啟動子互作蛋白篩選 通過酵母單雜交技術(shù)篩選出與VvFT啟動子互作的蛋白,具體操作:將cDNA文庫和pGADT7-Rec線性化質(zhì)粒共轉(zhuǎn)化陽性誘餌菌株Y1H-pAbAi-pVvFT感受態(tài)細(xì)胞,取150 μL轉(zhuǎn)化菌液涂布于SD/-Leu/AbA(500 ng/mL)培養(yǎng)基上,30 ℃培養(yǎng)3 d,挑選陽性克隆至YPDA液體培養(yǎng)基擴(kuò)大培養(yǎng)3 d后抽提質(zhì)粒,并利用獵物質(zhì)粒pGADT7-T的通用引物(T7:5'-TAATACGACTCAC TATAGGGCGAGCGCCGCCATG-3'和ADR:5'-GTG AACTTGCGGGGTTTTTCAGTATCTACGATT-3')進(jìn)行PCR鑒定,以pGADT7-T質(zhì)粒為模板作為陽性對照,以水為模板作為陰性對照。PCR產(chǎn)物用1%瓊脂糖凝膠電泳檢測,將電泳圖譜中500~2000 bp間有條帶的質(zhì)粒送北京六合華大基因科技股份有限公司測序。利用NCBI的BLASTx在線工具對cDNA插入片段進(jìn)行序列比對,對其進(jìn)行功能注釋,從而篩選出與VvFT基因啟動子互作的蛋白(鄒禹等,2019)。
1. 2. 6 酵母單雜交點(diǎn)對點(diǎn)驗(yàn)證互作蛋白 根據(jù)NCBI數(shù)據(jù)庫中VvDnaJ10基因(GenBank登錄號XM_010665750.2)序列設(shè)計(jì)PCR引物,VvDnaJ10-F:5'-GGAATTCCATATGGTGAAGGAGACAGAATACT ATG-3'(下劃線為Nde I酶切位點(diǎn))和VvDnaJ10-R:5'-CCGCTCGAGTCACTCTCTGCCTGTTGAAG-3'(下劃線為Xho I酶切位點(diǎn))。以巨峰葡萄冬芽總DNA為模板克隆VvDnaJ10基因,連接至pMD18-T上后進(jìn)行測序鑒定。用限制性內(nèi)切酶Nde I和Xho I對測序正確的pMD18-T-VvDnaJ10重組質(zhì)粒和pGADT-7空載體進(jìn)行雙酶切,回收目的片段進(jìn)行連接,以構(gòu)建獵物質(zhì)粒pGADT7-VvDnaJ10,將其轉(zhuǎn)化Y1H-pAbAi-pVvFT菌株感受態(tài)細(xì)胞,涂布于SD/-Leu和SD/-Leu/AbA(200 ng/mL)培養(yǎng)基,30 ℃培養(yǎng)3 d,觀察菌斑生長情況。以陽性質(zhì)粒pGADT7-p53轉(zhuǎn)化Y1H-pAbAi-p53菌株為陽性對照、獵物空載體pGADT-7轉(zhuǎn)化Y1H-pAbAi-p53菌株為陰性對照。
2 結(jié)果與分析
2. 1 VvFT基因啟動子序列分析
以巨峰葡萄冬芽總DNA為模板克隆VvFT基因啟動子,經(jīng)測序鑒定該序列長1466 bp。利用PlantCARE數(shù)據(jù)庫在線分析VvFT基因啟動子的順式作用調(diào)控元件,結(jié)果(表1)顯示,共預(yù)測到13種順式作用調(diào)控元件,包括A-box、CAAT-box和TATA-box組成型調(diào)控元件;光響應(yīng)調(diào)控元件ATC-motif、Box 4、G-Box和GT1-motif;茉莉酸甲酯(MeJA)響應(yīng)調(diào)控元件CGTCA-motif和TGACG-motif;干旱誘導(dǎo)的MYB結(jié)合位點(diǎn)元件MBS;玉米蛋白代謝必需的調(diào)控元件O2-site;參與生物鐘控制的調(diào)控元件circadian;厭氧誘導(dǎo)必需調(diào)控元件ARE,推測VvFT基因啟動子區(qū)域具有潛在調(diào)節(jié)因子結(jié)合的結(jié)構(gòu)基礎(chǔ)。
2. 2 誘餌菌株Y1H-pAbAi-pVvFT構(gòu)建
使用T4 DNA連接酶將VvFT基因啟動子序列(1466 bp)與pAbAi質(zhì)粒連接構(gòu)建誘餌載體pAbAi-pVvFT,用限制性內(nèi)切酶Bstb I線性化后轉(zhuǎn)化Y1HGold酵母感受態(tài)細(xì)胞,涂布于SD/-Ura培養(yǎng)基上培養(yǎng)3 d,挑取單菌落進(jìn)行PCR驗(yàn)證,結(jié)果顯示成功構(gòu)建Y1H-pAbAi-pVvFT誘餌菌株。將其涂布于SD/-Ura和SD/-Ura/AbA(500 ng/mL)培養(yǎng)基上培養(yǎng),結(jié)果(圖1)顯示,當(dāng)AbA濃度為500 ng/mL時(shí)完全抑制酵母單菌落生長,因此確定AbA的工作濃度為500 ng/mL。
2. 3 cDNA文庫構(gòu)建及互作蛋白篩選
提取的葡萄冬芽總RNA電泳檢測結(jié)果(圖2)顯示,28S rRNA條帶的亮度約是18S rRNA的2倍,說明總RNA的完整性良好;OD260/OD280為1.94,濃度為4799 ng/μL,說明RNA純度質(zhì)量好,可用于cDNA文庫的構(gòu)建。以純化的mRNA為模板,通過逆轉(zhuǎn)錄和LD-PCR獲得雙鏈cDNA,再利用CHROMA SPIN TE-400層析柱純化雙鏈 cDNA,用于構(gòu)建葡萄冬芽cDNA文庫。將cDNA文庫和線性化pGADT7-Rec質(zhì)粒共轉(zhuǎn)化Y1H-pAbAi-pVvFT感受態(tài)細(xì)胞,涂布于SD/-Leu/AbA(500 ng/mL)培養(yǎng)基上,30 ℃培養(yǎng)3 d,提取陽性克隆質(zhì)粒進(jìn)行PCR鑒定,PCR產(chǎn)物用瓊脂糖凝膠電泳檢測,結(jié)果如圖3所示。cDNA插入片段的大小不一,陽性克隆所含質(zhì)粒攜帶基因大小為500~2000 bp。將38個(gè)陽性克隆質(zhì)粒進(jìn)行測序,結(jié)果獲得34條表達(dá)序列標(biāo)簽(EST)序列,其中100~500 bp序列占7.7%;501~1000 bp序列占76.9%;大于1000 bp序列占15.3%。
2. 4 EST序列的BLASTx分析和功能注釋結(jié)果
對測序獲得34條EST序列進(jìn)行BLASTx比對搜索,篩選出期望值e-10以下的序列進(jìn)行同源對比,并對其進(jìn)行功能注釋,結(jié)果發(fā)現(xiàn)21條EST為未知功能序列,其余13條EST被功能注釋(表2)。13條EST序列與同源基因表現(xiàn)出較高的相似性,僅ft64序列與同源基因的相似性為93%,其他EST序列與同源基因的相似性均大于95%,尤其是ft15和ft41序列與同源基因的相似性高達(dá)100%。13條EST序列中,38.46%與植物生長、抗逆防御、信號轉(zhuǎn)導(dǎo)及轉(zhuǎn)錄調(diào)控相關(guān),其中ft49(休眠相關(guān)蛋白)與植物休眠相關(guān),ft64(NAP1相關(guān)蛋白)和ft44(GRF1互作因子3)與植物器官生長發(fā)育相關(guān),ft70(分子伴侶DnaJ10)與高溫脅迫和花芽分化相關(guān),ft41(轉(zhuǎn)錄抑制因子ILP1)與基因轉(zhuǎn)錄調(diào)節(jié)相關(guān);38.46%的EST被注釋為蛋白酶,包括肽蛋氨酸亞砜還原酶B5(ft15)、角鯊烯環(huán)氧酶3(ft19)、S-腺苷甲硫氨酸合成酶(ft42)、氧依賴的糞卟啉原-III氧化酶(ft60)和超氧化物歧化酶(ft68)。
2. 5 VvDnaJ10與VvFT基因啟動子互作驗(yàn)證結(jié)果
采用同源克隆的方法獲得VvDnaJ10基因。通過酵母單雜交點(diǎn)對點(diǎn)鑒定VvDnaJ10與VvFT基因啟動子間是否存在互作。將獵物質(zhì)粒pGADT7-VvDnaJ10轉(zhuǎn)化Y1H-pAbAi-pVvFT菌株感受態(tài)細(xì)胞,取不同稀釋倍數(shù)(10-1、10-2、10-3和10-4倍)的感受態(tài)細(xì)胞涂布于SD/-Leu和SD/-Leu/AbA(200 ng/mL)培養(yǎng)基上,結(jié)果(圖4)顯示,轉(zhuǎn)化菌均在SD/-Leu和SD/-Leu/AbA(200 ng/mL)培養(yǎng)基上有菌落生長,而轉(zhuǎn)化獵物空載體pGADT-7的Y1H-pAbAi-pVvFT和Y1H-pAbAi-p53菌株感受態(tài)細(xì)胞在SD/-Leu/AbA(200 ng/mL)培養(yǎng)基上均不能生長,表明獵物蛋白VvDnaJ10與VvFT基因啟動子之間相互作用激活了報(bào)告基因AbA的表達(dá),從而證明VvDnaJ10與VvFT基因啟動子存在互作。
3 討論
基因表達(dá)調(diào)控網(wǎng)絡(luò)由順反作用因子構(gòu)成。葡萄VvFT基因啟動子上游存在13種順式調(diào)控元件。CGTCA-motif和TGACG-motif為MeJA響應(yīng)元件。MeJA參與植物根的生長、逆境脅迫及開花時(shí)間的調(diào)控(張旺等,2000;Rakwal et al.,2002;閆志強(qiáng)等,2014)。據(jù)文獻(xiàn)報(bào)道,水稻噴施MeJA不僅有效促進(jìn)花期提前(閆志強(qiáng)等,2014),還可誘導(dǎo)粳稻不育系開穎,提高作物產(chǎn)量(張旺等,2000)。植物轉(zhuǎn)錄因子MYB參與花藥和花粉的分化發(fā)育調(diào)控(錢景華等,2016)。VlFT基因啟動子上游的MYB結(jié)合位點(diǎn)CAACTG是葡萄控制花器官性別分化的結(jié)構(gòu)基礎(chǔ)之一。
ILP1是一種轉(zhuǎn)錄抑制因子,與GCF(GC-binding factor)的C端結(jié)構(gòu)域同源。GCF也是一種轉(zhuǎn)錄抑制因子,可與表皮生長因子受體(Epidermal growth factor receptor,EGFR)、β-actin和鈣依賴蛋白酶基因啟動子區(qū)域的GC-rich序列相結(jié)合(Kageyama and Pastan,1989)。核內(nèi)再復(fù)制是細(xì)胞周期的一種,從常規(guī)的有絲分裂細(xì)胞周期進(jìn)入可能涉及不同的細(xì)胞周期相關(guān)基因表達(dá)。CYCLINA2(CYCA2)家族的所有成員在ILP1過表達(dá)系中的表達(dá)均降低。擬南芥中CYCA2;1表達(dá)的缺失導(dǎo)致多倍體的增加,證明ILP1通過調(diào)控CYCA2基因轉(zhuǎn)錄來控制核內(nèi)再復(fù)制(Imai et al.,2006)。
轉(zhuǎn)錄共激活因子GIF,即GRF相互作用因子(GRF-interacting factor)是細(xì)胞增殖的正向調(diào)節(jié)因子,在植物體側(cè)器官生長發(fā)揮重要作用。GIF蛋白家族由GIF1、GIF2和GIF3組成,與生長調(diào)節(jié)因子GRF形成功能復(fù)合體(Kim and Kende,2004;Horiguchi et al.,2005;Lee et al.,2009)。擬南芥中g(shù)if1 gif2 gif3三重突變體表現(xiàn)出嚴(yán)重的花藥結(jié)構(gòu)和功能缺陷,既不產(chǎn)生小孢子囊,也不產(chǎn)生花粉粒(Lee et al.,2014)?;蛐蛄蟹治霰砻?,GIF1是人類SYT(Synovial sarcoma translocation)轉(zhuǎn)錄共激活子的功能同源物。Kim和Kende(2004)研究發(fā)現(xiàn)GIF1蛋白的N端區(qū)域參與其與GRF1的相互作用。grf突變體和gif1突變體的葉片和花瓣較野生型窄,且gif1與grf突變組合表現(xiàn)出協(xié)同效應(yīng)。gif1和grf三倍體的窄葉表型是由沿葉寬軸的細(xì)胞數(shù)量減少引起。因此,GRF1和GIF1分別是轉(zhuǎn)錄激活因子和共激活因子,為調(diào)控葉子和花瓣生長及形狀復(fù)合物的一部分。
組蛋白伴侶伴隨初生組蛋白從細(xì)胞質(zhì)到細(xì)胞核,參與DNA復(fù)制、修復(fù)和基因轉(zhuǎn)錄過程中染色質(zhì)的動態(tài)調(diào)控(Ransom et al.,2010;Avvakumov et al.,2011;Zhu et al.,2013)。NAP1屬于H2A-H2B組蛋白分子伴侶。在擬南芥中NAP1相關(guān)蛋白(NAP1-rela-ted protein,NRP)NRP1和NRP2的雙突變體nrp1-1nrp2-1的根尖細(xì)胞周期在G2/M時(shí)停止,植株表現(xiàn)出短根和異位根毛等異常表型,進(jìn)一步分析發(fā)現(xiàn)根毛形成關(guān)鍵轉(zhuǎn)錄因子基因GLABRA2(GL2)表達(dá)水平下降;染色質(zhì)免疫共沉淀(ChIP)檢測結(jié)果顯示,NRP1和NRP2與位于轉(zhuǎn)錄活躍的常染色質(zhì)上的基因相結(jié)合(Zhu et al.,2006)。Zhu等(2017)研究證實(shí),NRP1在體內(nèi)與轉(zhuǎn)錄因子WER相互作用,并以WER依賴的方式在GL2基因啟動子區(qū)域富集,經(jīng)結(jié)晶學(xué)分析發(fā)現(xiàn),NRP1通過N-末端的α-螺旋結(jié)構(gòu)形成二聚體,NRP1的突變體中α-螺旋二聚作用被破壞或C末端的酸性尾巴被移除,從而損害其與組蛋白和WER的結(jié)合,無法激活GL2基因轉(zhuǎn)錄,導(dǎo)致nrp1-1nrp2-1突變表型異常。干細(xì)胞生態(tài)位(SCN)的完整性對生物體的發(fā)育至關(guān)重要。H3/H4組蛋白伴侶染色質(zhì)組裝因子1(CAF-1)和H2A/H2B組蛋白伴侶NAP1相關(guān)蛋白1/2(NRP1/2)在擬南芥根SCN維持中發(fā)揮協(xié)同作用;與m56-1雙突變體(NRP1和NRP2缺失)和fas2-4突變體(CAF-1缺失)相比,m56-1fas2-4雙突變體的短根表型更嚴(yán)重(Ma et al.,2018)。
DnaJ蛋白家族屬于熱休克蛋白(Heat-shock proteins,HSPs),作為分子伴侶,其單獨(dú)或與HSP70伴侶相結(jié)合,參與植物發(fā)育、信號轉(zhuǎn)導(dǎo)和逆境脅迫的生理過程(Shen et al.,2011;Yang et al.,2009,2010;Zhou et al.,2012)。植物中SVP是抑制FT和SOC1(SUPPRESSOR of the OVEREXPRESSION of CO1)表達(dá)的關(guān)鍵開花調(diào)控因子。Shen等(2011)研究發(fā)現(xiàn)擬南芥中的開花啟動子DnaJ同源蛋白3(J3)通過與SVP的相互作用介導(dǎo)開花信號的整合;J3在細(xì)胞核中直接與SVP相互作用,阻止SVP與SOC1和FT調(diào)節(jié)序列相結(jié)合,上調(diào)SOC1和FT基因表達(dá)從而實(shí)現(xiàn)花期轉(zhuǎn)變,而J3功能的喪失導(dǎo)致出現(xiàn)晚花表型,推測是由于SOC1和FT的表達(dá)降低導(dǎo)致。DnaJ蛋白是細(xì)胞的壓力傳感器,其表達(dá)受熱、強(qiáng)光和低溫誘導(dǎo)(Piippo et al.,2006;Scarpeci et al.,2008;Rajan and DSilva,2009)。高溫脅迫常引起植物蛋白質(zhì)的變性。因此,維持蛋白質(zhì)的功能構(gòu)象對植物在高溫脅迫下的生存尤為重要(Lee and Vierling,2000;Yang et al.,2010)。研究發(fā)現(xiàn),DnaJ蛋白在重建正常蛋白構(gòu)象和細(xì)胞蛋白穩(wěn)態(tài)過程中發(fā)揮分子伴侶的作用(Wang et al.,2004);編碼擬南芥DnaJ蛋白的TMS1基因在花粉管的耐熱性中發(fā)揮重要調(diào)控作用(Yang et al.,2009);敲除AtDjB1基因會降低擬南芥的耐熱性(Zhou et al.,2012 )。
為了探究調(diào)控葡萄開花時(shí)間核心基因VvFT的分子調(diào)控機(jī)制,更多直接或間接參與調(diào)節(jié)開花時(shí)間的調(diào)控因子有待挖掘。進(jìn)一步通過基因遺傳轉(zhuǎn)化及表觀遺傳學(xué)分析等技術(shù)手段驗(yàn)證候選調(diào)控基因的生物學(xué)功能,為研究VvFT基因的功能和分子機(jī)理提供參考。
4 結(jié)論
通過葡萄冬芽cDNA文庫構(gòu)建及酵母單雜交技術(shù)篩選出13個(gè)與VvFT啟動子區(qū)域結(jié)合的潛在調(diào)控因子基因,其在植物生長、抗逆防御、信號轉(zhuǎn)導(dǎo)、轉(zhuǎn)錄調(diào)控、蛋白酶等方面均有已知或預(yù)測功能的候選調(diào)控因子基因。雖然大部分基因預(yù)測功能與VvFT調(diào)控開花時(shí)間無明顯的直接關(guān)系,但研究結(jié)果為進(jìn)一步探索VvFT轉(zhuǎn)錄或表達(dá)水平控制葡萄開花時(shí)間的分子機(jī)制提供了候選基因。
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(責(zé)任編輯 陳 燕)