田玉富 崔璨 謝龍飛等
摘要從吉爾吉斯白樺轉錄組文庫測序中獲得白樺BkWRKY1轉錄因子的cDNA序列,該序列包含2 189個堿基。序列比對和同源性分析表明,該基因cDNA序列包含1 728 bp的開放閱讀框,可編碼575個氨基酸,5′非翻譯區(UTR)為119 bp,3′非翻譯區(UTR)為342 bp。該基因屬于WRKY transcription factor家族,含有2個WRKY結構域,蛋白分子量為62.483 kD,理論等電點為7.32,負電荷殘基(Asp+Glu)總數為62個,正電荷殘基(Arg+Lys)總數為62個。蛋白不含有信號肽,具有一定的親水性,為親水蛋白,無跨膜結構。同源性比較與進化樹分析表明,吉爾吉斯白樺WRKY蛋白與大豆和蒺藜苜蓿的WRKY蛋白在進化上關系較近。該基因在0.6%NaHCO3脅迫處理后表達量增加,為上調表達基因。
關鍵詞吉爾吉斯白樺;WRKY轉錄因子;生物信息學分析
中圖分類號S188文獻標識碼A文章編號0517-6611(2014)23-07703-07
基金項目中央高校基本科研業務費專項資金項目(DL12CA13);東北林業大學大學生創新訓練項目(201310225101)。
作者簡介田玉富(1991- ),男,寧夏同心人,本科生,專業:林學。*通訊作者,碩士研究生,從事植物資源學領域的研究。
收稿日期20140709在眾多的轉錄因子中,WRKY轉錄因子是當前研究較為廣泛的植物特有的轉錄因子,最初是從甜馬鈴薯[1]、野燕麥[2]、歐芹[3]和擬南芥[4]中克隆獲得,由于其蛋白含有高度保守的60個氨基酸組成的WRKY結構域而將其命名為WRKY轉錄因子[5]。WRKY結構域的核心序列靠近氨基(N)末端,由WRKYGQK等7個保守的氨基酸殘基組成,能夠與基因啟動子中的(T)(T)TGAC(C/T)序列(W盒)發生特異性結合,從而調節基因的表達,參與多種與植物生長發育、脅迫應答和物質代謝等有關的重要生理過程;而鋅指結構位于羧基(C)末端。根據WRKY轉錄因子中WRKY結構域的個數以及鋅指的類型將其分為3個大組。1.1試驗材料一年生吉爾吉斯白樺(Betula kirghisorum)葉片。
1.2方法
1.2.1BkWRKY1基因的克隆及序列分析。構建了0.6% NaHCO3 脅迫下吉爾吉斯白樺葉片組織的轉錄組測序文庫,通過對轉錄組文庫隨機測序,獲得BkWRKY1基因cDNA序列。采用NCBI 的開放讀碼框(ORF founder)尋找軟件(http://www.ncbi.nlm.nih.gov/gorf/gorf.html),確定該基因的開放讀碼框;采用ProtParam(http://web.expasy.org/protparam/)軟件計算該基因的分子量、等電點、親水性。
1.2.2BkWRKY1蛋白家族、保守區及二級結構預測。采用pfam27.0(http://pfam.sanger.ac.uk/)軟件預測蛋白家族,采用BlastP(http://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi)預測保守區,采用SOPMA(http://npsa-pbil.ibcp.fr/cgi-bin /secpred_sopma.pl)預測BkWRKY1蛋白的二級結構。
1.2.3BkWRKY1信號肽、疏水性及跨膜結構預測。采用SignalP4.1(http://www.cbs.dtu.dk/services/SignalP/)進行信號肽預測,采用ProScal(http://web.expasy.org/protscale/)進行蛋白疏水性預測。用TMHMM程序(http://www.cbs.dtu.dk/services/TMHMM)對BkWRKY1進行跨膜結構預測。
1.2.4序列相似性分析及進化樹的構建。采用BlastP尋找相似性序列,并選擇與其相似性高的10種不同植物WRKY蛋白的氨基酸序列,采用ClustalW2(http://www.ebi.ac.uk/Tools /msa/ clustalw2/)進行多序列比對;同時用MEGA6軟件構建上述11種植物WRKY蛋白的氨基酸序列系統進化樹。
1.2.50.6% NaHCO3脅迫處理前后基因表達量的分析。基因表達量的計算使用RPKM法[8],以RPKM值估計BkWRKY1基因的表達量,基因表達量符合FDR≤0.001,且log2Ratio|≥1的基因為顯著差異表達基因。其中,Ratio為脅迫處理后RPKM值與對照組RPKM值的比值,log2Ratio為0.6%NaHCO3脅迫處理后BkWRKY1基因相對于對照組BkWRKY1基因表達量的變化。
2結果與分析
2.1吉爾吉斯白樺BkWRKY1基因序列與推斷的氨基酸序列從鹽脅迫后的吉爾吉斯白樺葉片轉錄組文庫中測序獲得了BkWRKY1基因的cDNA序列,測序結果顯示,該基因cDNA包含2 189個堿基,序列比對和同源性分析表明,該基因cDNA序列包含1 728 bp的開放閱讀框,編碼575個氨基酸,5′非翻譯區(UTR)為119 bp,3′非翻譯區(UTR)為342 bp。ProtParam 預測該蛋白的分子量為62.483 kD,理論等電點為7.32,負電荷殘基(Asp+Glu)總數為62個,正電荷殘基(Arg+Lys)總數是62個。
2.2蛋白家族、保守區及二級結構預測對獲得的基因推導的氨基酸序列用BlastP預測蛋白保守區,發現了WRKY結構域,位于227~285、402~461氨基酸之間含有WRKY蛋白的保守序列,pfam蛋白預測表明,與其對應的蛋白質家族WRKY DNA-domain family,以上分析表明該基因屬于WRKY transcription factor家族。SOPMA軟件預測結果表明BkWRKY1蛋白的二級結構以隨機卷曲為主。注:ATG為起始密碼子;*為終止密碼子。
圖2BkWRKY1基因的cDNA序列及由此推導的氨基酸序列2.3信號肽、疏水性及跨膜結構分析通過signalp 4.1預測,該蛋白不含有信號肽。ProScal蛋白親水、疏水性預測表),蛋白疏水性最大值:1.789,疏水性最小值:-3.389,疏水平均值為-0.800,具有一定的親水性。并根據ProtParam軟件預測Grand average of hydropathicity(GRAVY):-0.777,所以該蛋白質為親水蛋白。TMHMM程序預測結果表明,在BkWRKY1長度為575個氨基酸的蛋白序列中無跨膜結構。
2.4吉爾吉斯白樺等物種BkWRKY1基因的多序列比對分析用推導的氨基酸序列與蛋白質數據庫進行同源性比較,其氨基酸序列與川桑(Morus notabilis,EXB67429.1)、煙草(Theobroma cacao,XP_007020620.1)、蓖麻(Ricinus communis、XP_002529048.1)、甜橙(Citrus sinensis,XP_006474948.1)、草莓(Fragaria vesca,XP_004294460.1)、大豆(Glycine max,XP_003553015.1)、葡萄(Vitis vinifera,XP_002274204.2)、麻風樹(Jatropha curcas,AGJ52155.1)、楊樹(Populus trichocarpa,XP_002298853.1)、蒺藜苜蓿(Medicago truncatula,XP_ 003600259.1)等植物WRKY轉錄因子的氨基酸序列進行兩兩比對,相似系數分別為72%、71%、70%、69%、69%、68%、68%、68%、66%、66%,相似性較高。氨基酸序列多重比對結果用MEGA6軟件對該基因及其他物種WRKY轉錄因子的氨基酸序列進行多序列比對,繪制分子進化樹,進化分析結果表明,吉爾吉斯白樺WRKY蛋白與大豆和蒺藜苜蓿的WRKY蛋白在進化上關系較近。
疏水性分析42卷23期田玉富等吉爾吉斯白樺BkWRKY1基因克隆與序列分析2.50.6% NaHCO3脅迫處理后BkWRKY1基因的表達量測得BkWRKY1基因對照組和脅迫處理后的RPKM值分別為19.803 1和23.622 4,log2Ratio為0.254 4,表明該基因在0.6% NaHCO3脅迫處理后表達量增加,為上調表達基因(圖8)。
3結論與討論
以白樺轉錄組文庫獲得的基因序列為信息來源,從中克隆得到了白樺BkWRKY1基因,屬于WRKY family transcription factor家族,該基因含有2個WRKY結構域,可編碼575個氨基酸,對應蛋白的分子量為62.483 kD,理論等電點為7.32,蛋白不含有信號肽,具有一定的親水性,為親水蛋白,不含有跨膜結構。同源性比較與進化樹分析表明,吉爾吉斯白樺WRKY蛋白與大豆和蒺藜苜蓿的WRKY蛋白在進化關系上較近。0.6%NaHCO3脅迫處理后BkWRKY1基因上調表達。
WRKY轉錄因子在植物界中分布廣泛,目前,發現辣椒[9]、油菜[10]、玉米[11]、番木瓜[12]、苜蓿[13]、楊樹[14]、蘋果[15]、森林草莓[16]、水稻[17]等多個種屬植物中均含有WRKY轉錄因子。WRKY轉錄因子參與植物的多種生理生化與生長發育過程,在植物應對外界逆境脅迫時發揮十分重要的功能。如參與側根的生長[18-20],調控衰老反應[21-23],調控新陳代謝[24-25],抑制種子的萌發[26-29],調控非生物脅迫[30-33],參與生物脅迫[34-49],參與抗病相關信號轉導途徑[50-55]。在鹽脅迫條件下,許多植物組織器官中的WRKY基因能夠作出積極的響應,上調或下調表達。QIU等[56]研究水稻中13個WRKY基因,指出其中9個基因能對NaCl做出響應;研究發現擬南芥可以忍受150 mmol/L NaCl脅迫,脅迫處理后WRKY17和WRKY33上調表達,WRKY17在誘導脅迫6h時達最高峰隨后逐漸降低,而WRKY33的豐度在整個處理過程都保持很高;處理48h時WRKY25表達至最高峰,WRKY轉錄因子在鹽脅迫反應中具有重要作用[57]。150 mmol/L NaCl脅迫下,小麥根中WRKY基因表達量隨脅迫時間的延長而逐漸增加;莖中WRKY基因在脅迫1 h時達到最大值,而隨脅迫時間的延長逐漸下降,由此可知對于鹽脅迫,其根比莖敏感[58]。 珠美海棠幼苗在150 mmol/L NaCl脅迫處理后,MzWRKY19~MzWRKY27等共8個基因的表達無明顯變化;葉片中有15個WRKY基因的表達受鹽脅迫誘導、1個基因受鹽脅迫抑制、9個基因的表達無明顯變化[59]。200 mmol/L NaCl能強烈誘導MhWRKY40b表達,且脅迫6h時基因相對表達量達到最高,說明MhWRKY40b能夠響應鹽脅
圖6氨基酸序列的多重比對圖7白樺等11個物種的WRKY序列的系統進化樹圖80.6%NaHCO3脅迫處理后BkWRKY1基因的表達量迫,并有可能在鹽脅迫反應中起到了重要調控作用[60]。
吉爾吉斯白樺BkWRKY1能夠對0.6%NaHCO3脅迫作出上調表達的響應,但具體的響應機制還不清楚。因此,有待于進一步研究鹽脅迫條件下吉爾吉斯白樺BkWRKY1基因及WRKY家族其他成員在抗鹽過程中的功能,為選育抗鹽堿的樺樹品種提供試驗依據。
參考文獻
[1] 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,1994,244:563-571.
[2] 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 a-Amy2 genes[J].Plant Molecular Biology,1995,29(4):691-702.
[3] 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].The EMBO Journal,1996,15(20):5690-5700.
[4] PATER S D,GRECO V,PHAM K,et al.Characterization of a zinc-Dependent transcriptional activator from Arabidopsis[J].Nucleic Acids Resarch,1996,24(23):4624-4631.
[5] EULGEM T,RUSHTON P J,SCHMELZER E,et al.Early nuclear events in plant defense signaling:rapid gene activation by WRKY transcription factors[J].EMBO Journal,1999,18(17):4689-4699.
[6] 賈翠玲,侯和勝.植物WRKY轉錄因子的結構特點及其在植物防衛反應中的作用[J].天津農業科學,2010,16(2):21-26.
[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):200-206.
[8] MORTAZAVI A,WILLIAMS B A,MCCUE K,et al.Mapping and quantifying mammalian transcriptomes by RNA-Seq.Nat Methods,2008,5(7):621-628.
[9] 王育娜.辣椒WRKY轉錄因子cDNA的分離與功能鑒定[D].福州:福建農林大學,2008.
[10] 薛華,張紅巖,李小艷,等.油菜矮稈突變WRKY轉錄因子cDNA克隆及表達分析[J].西北植物學報,2008,28(3):452-458.
[11] 黎華.玉米WRKY家族轉錄因子基因ZmWRKY33的克隆及功能分析[D].揚州:揚州大學,2011.
[12] 潘林杰.番木瓜WRKY轉錄因子的基因表達譜及其功能的初步研究[D].武漢:華中農業大學,2011.
[13] 江騰,林勇祥,劉雪,等.苜蓿全基因組WRKY轉錄因子基因的分析[J].草業學報,2011,20(3):211-218.
[14] 何紅升.楊樹全基因組WRKY基因的鑒定及表達分析[D].合肥:安徽農業大學,2012.
[15] 許瑞瑞,張世忠,曹慧,等.蘋果WRKY轉錄因子家族基因生物信息學分析[J].園藝學報,2012,39(10):2049-2060.
[16] 苗立祥,張豫超,楊肖芳,等.森林草莓全基因組WRKY轉錄因子基因的鑒定與分析[J].核農學報,2012,26(8):1124-1131.
[17] 鄂志國,王磊.水稻WRKY基因家族功能研究進展[J].核農學報,2012,26(5):750-755.
[18] ZHOU Q Y,TIAN A G,ZOU H F,et al.Soybean WRKY-type transcription factor genes,GmWRKY13,GmWRKY21,and GmWRKY54,confer differential tolerance to abiotic stresses in transgenic Arabidopsis plants[J].Plant Biotechnology Journal,2008,6(5):486-503.
[19] DEVAIAH B N,KARTHIKEYAN A S,RAGHOTHAMA K G.WRKY75 transcription factor is a modulator of phosphate acquisition and root development in Arabidopsis[J].Plant Physiology,2007,143(4):1789-1801.
[20] ZHANG J,PENG Y L,GUO Z J.Constitutive expression of pathogen-inducible OsWRKY31 enhances disease resistance and affects root growth and auxin response in transgenic rice plants[J].Cell Research,2008,18(4):508-521.
[21] ROBATZEK S,SOMSSICH I E.A new member of the Arabidopsis WRKY transcription factor family,AtWRKY6,is associated with both senescence- and defence-related processes[J].Plant Journal,2001,28(2):123-133.
[22] ULKER B,MUKHTAR M S,SOMSSICH I E.The WRKY70 transcription factor of Arabidopsis influences both the plant senescence and defense signaling Pathways[J]. Planta,2007,226(1):125-137.
[23] JING S J,ZHOU X,SONG Y,et al.Heterologous expression of OsWRKY23 gene enhances pathogen defense and dark-induced leaf senescence in Arabidopsis[J].Plant Growth Regulation,2009,58(2):181-190.
[24] SUN C,PALMQVIST S,OLSSON H,et al.A novel WRKY transcription factor,SUSIBA2,participates in sugar Signaling in barley by binding to the sugar-responsive elements of the iso1 promoter[J].Plant Cell,2003,15(9):2076-2092.
[25] XU Y H,WANG J W,WANG S,et al.Characterization of GaWRKY1,a cotton transcription factor that regulates the sesquiterpene Synthase gene(+)-δ-cadinene synthase-A[J].Plant Physiology,2004,135(1):507-515.
[26] ZHANG Z L,XIE Z,ZOU X L,et al.A rice WRKY gene encodes a transcriptional repressor of the gibberellin signaling Pathway in aleurone cells[J].Plant Physiology,2004,134(4):1500-1513.
[27] XIE Z,ZHANG Z L,ZOU X L,et al.Interactions of two abscisic-acid induced WRKY genes in repressing gibberellin Signaling in aleurone cells[J].The Plant Journal,2006,46(2):231-242.
[28] XIE Z,ZHANG Z L,HANZLIK S,et al.Salicylic acid inhibits gibberellin-induced alpha-amylase expression and seed germination via a Pathway involving an abscisic- acid-inducible WRKY gene[J].Plant Molecular Biology,2007,64(3):293-303.
[29] ZOU X,NEUMAN D,SHEN Q J.Interactions of two transcriptional repressors and two transcriptional activators in modulating gibberellin signaling in aleurone cells[J].Plant Physiology,2008,148(1):176-186.
[30] WEI W,ZHANG Y,HAN L,et al.A novel WRKY transcriptional factor from Thlaspi caerulescens negatively regulates the osmotic Stress tolerance of transgenic tobacco[J].Plant Cell reports,2008,27(4):795-803.
[31] CHEN Y F,LI L Q,XU Q,et al.The WRKY6 transcription factor modulates PHOSPHATE1 expression in response to Low Pi stress in Arabidopsis[J].The Plant Cell Oline,2009,21(11):3554-3566.
[32] JIANG Y,DEYHOLOS M K.Functional characterization of Arabidopsis NaCl- inducible WRKY25 and WRKY33 transcription factors in abiotic stresses[J].Plant Molecular Biology,2009,69(1/2):91-105.
[33] 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 reports,2009,28(1):21-30.
[34] YANG B,JIANG Y Q,RAHMAN M H,et al.Identification and expression analysis of WRKY transcription factor genes in canola(Brassica napus L.)in response to fungal pathogens and hormone treatments[J].BMC Plant Biology,2009,9(1):68.
[35] KIM K C,LAI Z,FAN B,et al.Arabidopsis WRKY38 and WRKY62 transcription factors interact with histone deacetylase 19 in basal defense[J].The Plant Cell Oline,2008,20(9):2357-2371.
[36] RYU H S,HAN M,LEE S K,et al.A comprehensive expression analysis of the W RKY gene superfamily in rice plants during defense response[J].Plant Cell Reports,2006,25(8):836-847.
[37] ZHENG Z,QAMAR S A,CHEN Z X,et al.Arabidopsis WRKY33 transcription factor is required for resistance to necrotrophic fungal pathogens[J].The Plant Journal,2006,48(4):592-605.
[38] KALDE M,BARTH M,SOMSSICH I E,et al.Members of the Arabidopsis WRKY group Ⅲ transcription factors are part of different plant defense signaling pathways [J].Molecular Plant-microbe Interactions,2003,16(4):295-305.
[39] KNOTH C,RINGLER J,DANGL J L,et al.Arabidopsis WRKY70 is required for full RPP4-mediated disease resistance and basal defense against Hyaloperonospora parasitica [J].Molecular Plant-microbe Interactions,2007,20(2):120-128.
[40] LIU X Q,BAI X Q,QIAN Q,et al.OsWRKY03,a rice transcriptional activator that functions in defense signaling pathway upstream of OsNPR1[J].Cell Research,2005,15(8):593-603.
[41] CATALINO N J,SOMSSICH I E,ROBY D,et al.The transcription factors WRKY11 and WRKY17 act as negative regulators of basal resistance in Arabidopsis thaliana[J].The Plant Cell Oline,2006,18(11):3289-3302.
[42] OH S K,YI S Y,YU S H,et al.CaWRKY2,a chili pepper transcription factor,is rap idly induced by incompatible plant pathogens[J].Molecular Cells,2006,22(1):58-64.
[43] XU X P,CHEN C H,FAN B F,et al.Physical and functional interactions between pathogen-induced Arabidopsis WRKY18,WRKY40,and WRKY60 transcription factors[J].The Plant Cell Oline,2006,18(5):1310-1326.
[44] LIPPOK B,BIRKENBIHL R P,RIVORY G,et al.Expression of AtWRKY33 encoding a pathogen- or PAMP-responsive WRKY transcription factor is regulated by a composite DNA motif containing W box elements[J].Molecular Plant-microbe Interactions,2007,20(4):420-429.
[45] ZHENG Z Y,MOSHER S L,FAN B F,et al.Functional analysis of Arabidopsis WRKY25 transcription factor in plant defense against Pseudomonas syringae[J].
BMC Plant Biology,2007,7(2):1-13.
[46] YANG P Z,CHEN C H,WANG Z,et al.A pathogen- and salicylic acid-induced WRKY DNA-binding activity recognizes the elicitor response element of the tobacco class I chitinase gene promoter[J].The Plant Journal,1999,18(2):141-149.
[47] YODA H,OGAWA M,YAMAGUCHI Y,et al.Identification of early-responsive genes associated with the hypersensitive response to tobacco mosaic virus and characterization of a WRKY-type transcription factor in tobacco plants[J].Molecular Genetics Genomics,2002,267(2):154-161.
[48] PARK C J,SHIN Y C,LEE B J,et al.A hot pepper gene encoding WRKY transcription factor is induced during hypersensitive response to tobacco mosaic virus and Xanthomonas campestris[J].Planta,2006,223(2):168-179.
[49] CORMACK R S,EULGEM T,RUSHTON P J,et al.Leucine zipper-containing WRKY proteins widen the spectrum of immediate early elicitor-induced WRKY transcription factors in parsley[J].Biochimica et Biophysica Acta,2002,1576(1):92-100.
[50] CHEN C H,CHEN Z X.Potentiation of developmentally regulated plant defense r esponse by AtWRKY18,a pathogen-induced Arabidopsis transcription factor[J].Plant Physiology,2002,129(2):706-716.
[51] LIU X Q,BAI X Q,WANG X J,et al.OsWRKY71,a rice transcription factor,is involved in rice defense response[J].Plant Physiology,2007,164(8):969-979.
[52] ISHIDA T,HATTORI S,SANO R,et al.Arabidopsis TRANSPARENT TESTA GLABRA2 is directly regulated by R2R3 MYB transcription factors and is involved in regulation of GLABRA2 transcription in epidermal differentiation[J].Plant Cell,2007,19(8):2531-2543.
[53] MCGRATH K C,DOMBRECHT B,MANNERS J M,et al.Repressor-and activator-type ethylene response factors functioning in jasmonate signaling and disease resistance identified via a genome-wide screen of Arabidopsis transcription factor gene expression[J].Plant Physiology,2005,139(2):949-959.
[54] MAO P,DUAN M R,WEI C H,et al.WRKY62 transcription factor acts down stream of cytosolic NPR1 and negatively regulates jasmonate-responsive gene expression[J].Plant Cell Physiology,2007,48(6):833-842.
[55] QIU D Y,XIAO J,DING X H,et al.OsWRKY13 mediates rice disease resistance by regulating defense-related genes in salicylate-and jasmonate-dependent signaling [J].Molecular Plant-microbe Interactions,2007,20(5):492-499.
[56] QIU Y,JING S,FU J,et al.Cloning and analysis of expression profile of 13WRKY genes in rice[J].Chinese Science Bulletin,2004,49(20):2159-2168.
[57] JIANG Y,DEYHOLOS M K.Comprehensive transcriptional profiling of NaCl- stressed Arabidopsis roots reveals novel classes of responsive genes[J].BMC Plant Biology,2006,6(1):25.
[58] KAWAURA K,MOCHIDA K,OGIHARA Y.Genome-wide analysis for identification of salt-responsive genes in common wheat[J].Functional & Integrative Genomics,2008,8(3):277-286.
[59] 蔣阿維,張素維,孫楊吾,等.珠美海棠MzWRKY基因家族鹽脅迫應答模式研究[J].園藝學報,2010,37(8):1213-1219.
[60] 羅昌國,渠慎春,張計育,等.湖北海棠MhWRKY40b在幾種脅迫下的表達分析[J].園藝學報,2013,40(1):1-9.安徽農業科學,Journal of Anhui Agri. Sci.2014,42(23):