实施例4:运用iTRAQ(isobaric tags for relative and absolutequantification)技术进行干旱处理和对照烟草材料的差异表达蛋白的筛选
标记采用8-plex标记,方法参考说明书,6个样本标记完以后等量混合。将混合后的样本分成12个组分,色谱仪是Thermo DINOEX Ultimate 3000 BioRS,分析柱是Durashell C18(5μm,100Å,4.6mm×250mm)。质谱仪是AB SCIEX nano LC-MS/MS(Triple TOF5600 plus),分析柱是AB SCIEX分析柱(75μm内径,充填3μm,120 Å的ChromXP C18柱料,长10cm),喷针是NEW objective(20μm内径,喷针口的直径是10μm),捕获柱是eksigentChromxp Trap Column(3μm C18-CL, 120 Å, 350μm×0.5mm)。LC-MS/MS条件:A: 0.1%甲酸,5%乙腈;B: 0.1%甲酸,95%乙腈;Loading Buffer: 0.1%甲酸,3%乙腈。LC-MS/MS的液相方法以90min为例,上样5μL。
取等量肽段(50μg)进行同位素标记,标记方案如表3所示。
表3 同位素标记方案
样品名称 |
样品描述 |
标记号码 |
T1 |
干旱处理的烟草叶片样品 |
113 |
T2 |
干旱处理的烟草叶片样品 |
114 |
T3 |
干旱处理的烟草叶片样品 |
115 |
CK1 |
正常生长烟草 |
116 |
CK2 |
正常生长烟草 |
117 |
CK3 |
正常生长烟草 |
118 |
本次实验采用基于质谱方法的蛋白质组鉴定基本流程,即对MS/MS质谱数据经过系列优化处理后与数据库进行相似性比较打分从而进行蛋白鉴定,该方法是目前应用最广也是业界公认的高通量鉴定蛋白质方法。具有鉴定准确度高,通量大,无需人工序列解析等优点。
使用与AB Sciex 5600 plus配套的搜索引擎——ProteinpilotTM V4.0.8085。Proteinpilot在搜索时由于考虑了全部可能的修饰种类,同时增加了自动容错匹配功能,在保证鉴定结果可信度的前提下,能够比同类软件检索到更多的结果。
对于Proteinpilot的鉴定结果,做了进一步过滤,对于鉴定到的蛋白,认为unusedscore≥1.3(即可信度水平在95%以上),每个蛋白至少包含一个unique肽段的蛋白为可信蛋白,不符合该条件的蛋白不包括在本报告中;对于鉴定的肽段,以conf≥95过滤,即可信度在95%以上认为可信肽段,对于蛋白质定量,为了得到更全面的关于某蛋白的定量信息,Proteinpilot软件使用了conf≥15的所有肽段。
本次实验中,质谱产生的二级谱图数、解析的二级谱图数分别为396496、125770,谱图鉴定率达到了31%以上,鉴定到的肽段和蛋白数总体情况请参见表4。
表4蛋白质鉴定信息统计总表
注:“*”表示可信度至少为95%,“**”表示至少含有2个unique肽段的鉴定蛋白质数目。
重复性分析指的是通过分析生物重复样品数据的再现性,以判断实验操作的重复性和仪器的稳定性,重复性分析可以从两个角度进行:同一样品不同生物重复的CV值分布的分析和样品间的相关性分析。
CV(Coefficient of Variation)变异系数可以反映数据的离散程度,是数据标准方差和平均值的比值,用百分数表示,具体表达式为
CV =(标准偏差 SD /平均值MEAN)×100%。
图2表示不同样品的CV值分布。从图2可见:CK样品的CV值主要集中在0%~20%,而T样品的CV值主要集中在0%~15%。相对来说,T样品的CV值更加集中在低值区域,说明T样品的重复性更好。
通过图3更加直观地显示出不同实验组CV值的对比,不同颜色的盒形图代表了不同实验组的CV分布,盒子的上下两边为上下四分位数线,盒子中间的黑色横线是数据中位数(数据中占据中间位置的数)。通过盒子的上下四分位数可以判断出:T样品的CV数据更加集中,这与图2的分析是一致的。通过盒子的中位数线可以判断出两组样品的CV值中位数都小于20%,图3自左向右2个盒子的CV中位数分别为9.96%和9%,说明重复性较好。
相关性分析可以衡量出不同样品之间的相关密切程度。图4综合反映了不同实验样品(m113:T1,m114:T2,m115:T3,m116:CK1,m117:CK2,m118:CK3)之间的两两相关性,其中对角线上的值代表了不同样品,下三角为两两样品之间的蛋白质丰度分布的线性回归拟合图,上三角的数字代表了两两样品之间的相关系数。从下三角可以看出不同样品之间数据都可以用一条直线很好地拟合,从上三角可以看出样品之间的相关系数都超过了0.9,说明样品间大部分蛋白质丰度未发生明显变化,且重复样品之间的相关系数达到了0.95以上,大于非重复样品之间的相关系数,说明重复性较好。
iTRAQ标记方法能够实现对多个样品同时进行相对定量,且定量具有较高的准确性。我们使用Proteinpilot软件实现蛋白质组iTRAQ定量。当差异倍数达到1.2倍及以上(即up_regulate≥1.2和down_regulate≤0.83),且经过显著性统计检验其q-value值≤0.01时,视为显著差异蛋白。
对于存在生物学重复或技术重复样品的设计,首先,利用待比较样品间所有重复样品每个蛋白质的肽段定量值进行t-检验,计算出P-value,并利用Benjamini-Hochberg多重假设检验的方法校正P值,得到校正后的P值——q-value。其次,计算各个重复样品相对应蛋白质定量值的中位数作为待比较样品的定量值,并据此计算待比较样品间蛋白的最终差异倍数。最后,根据差异倍数和q-value来筛选出差异蛋白。在差异倍数≥1.2或者≤0.83倍,q-value≤0.01的条件下,两两样品间蛋白显著差异数量如表5。
表5两两样品间蛋白显著差异数量
类 型 |
T/CK |
总定量数 |
5570 |
上调蛋白数量 |
260 |
下调蛋白数量 |
206 |
在差异表达蛋白质列表中,我们发现编号为3465的蛋白质在干旱处理烟草中表达明显上调,较未经处理的红花大金元上调9.94倍,t检验P值为4.29E-04,达到极显著水平。
随后,经过LC-MS/MS 质谱鉴定和数据库搜索得2个非重复肽段与蛋白质histoneH4 isoform X1型组蛋白相符,氨基酸覆盖率为54.42%,具体结果详见表6。histone H4isoform X1型组蛋白序列见SEQ ID NO:1。
表6 histone H4 isoform X1型组蛋白质谱鉴定结果
在差异表达蛋白质列表中,我们发现编号为1113的蛋白质在干旱处理烟草中表达明显上调,较未经处理的红花大金元上调2.38倍,t检验P值为1.35E-10,达到极显著水平。随后经过LC-MS/MS 质谱鉴定和数据库搜索得7个非重复肽段与蛋白质heat shockprotein 82相符,氨基酸覆盖率为54.42%,具体结果详见表7。heat shock protein 82蛋白序列见SEQ ID NO:2。
表7 heat shock protein 82蛋白质谱鉴定结果
综上所述,histone H4 isoform X1型组蛋白及heat shock protein 82蛋白在烟草干旱处理植株与未经处理植株存在差异表达,显然与烟草耐旱性有密切的相关性,因此其表达量可以作为一个指标用于烟草耐旱性检测。这对于利用传统杂交育种手段进行筛选耐旱烟草品种的技术人员来说是显而易见的。
虽然,有关histone H4 isoform X1型组蛋白及heat shock protein 82蛋白生物学功能及其相应的机制还有待进一步研究,但是将其作为检测烟草耐旱性标记物却是肯定的。
因此,本发明的histone H4 isoform X1型组蛋白及heat shock protein 82蛋白在烟草耐旱性检测中的应用可以简单、方便、快速、可靠、灵敏地检测烟草耐旱性,为筛选耐旱烟草品种以及辅助传统杂交育种提供一条全新的途径,适于大规模推广应用。
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序列表
SEQ ID NO:1
<110> 云南省烟草农业科学研究院
<120> 一种蛋白在烟草耐旱性检测中的应用
<130> 2015
<160> 2
<170> PatentIn version 3.3
<210> 1
<211> 103
<212> PRT
<213> Nicotiana sp.
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Gly Leu Ile Tyr Glu Glu Thr Arg Gly Val Leu Lys Val Phe Leu Glu
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SEQ ID NO:2
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<212> PRT
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Lys Glu Ile Phe Leu Arg Glu Leu Ile Ser Asn Ser Ser Asp Ala Leu
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Asp Lys Ile Arg Phe Glu Ser Leu Thr Asp Lys Ser Lys Leu Asp Ala
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Gln Pro Glu Leu Phe Ile Arg Leu Val Pro Asp Lys Ala Asn Lys Thr
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Leu Ser Ile Ile Asp Ser Gly Ile Gly Met Thr Lys Ala Asp Leu Val
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Asn Asn Leu Gly Thr Ile Ala Arg Ser Gly Thr Lys Glu Phe Met Glu
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Ala Leu Gln Ala Gly Ala Asp Val Ser Met Ile Gly Gln Phe Gly Val
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Gly Phe Tyr Ser Ala Tyr Leu Val Ala Glu Lys Val Ile Val Thr Thr
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Lys His Asn Asp Asp Glu Gln Tyr Val Trp Glu Ser Gln Ala Gly Gly
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Ser Phe Thr Val Thr Arg Asp Val Asn Gly Glu Gln Leu Gly Arg Gly
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Thr Lys Ile Thr Leu Phe Leu Lys Glu Asp Gln Leu Glu Phe Leu Glu
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Glu Arg Arg Ile Lys Asp Leu Val Lys Lys His Ser Glu Phe Ile Ser
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Tyr Pro Ile Tyr Leu Trp Thr Glu Lys Thr Thr Glu Lys Glu Ile Ser
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Asp Asp Glu Asp Asp Glu Pro Lys Lys Asp Glu Glu Gly Ala Val Glu
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Trp Leu Arg Lys Pro Glu Glu Ile Thr Lys Asp Glu Tyr Ala Ser Phe
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Tyr Lys Ser Leu Thr Asn Asp Trp Glu Asp His Leu Ala Val Lys His
290 295 300
Phe Ser Val Glu Gly Gln Leu Glu Phe Lys Ala Ile Leu Phe Val Pro
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Lys Arg Ala Pro Phe Asp Leu Phe Asp Thr Arg Lys Lys Met Asn Asn
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Ile Lys Leu Tyr Val Arg Arg Val Phe Ile Met Asp Asn Cys Glu Glu
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Leu Ile Pro Glu Tyr Leu Gly Phe Val Lys Gly Val Val Asp Ser Asp
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Asp Leu Pro Leu Asn Ile Ser Arg Glu Met Leu Gln Gln Asn Lys Ile
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Leu Lys Val Ile Arg Lys Asn Leu Val Lys Lys Cys Ile Glu Met Phe
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Asn Glu Ile Ala Glu Asn Lys Glu Asp Tyr Asn Lys Phe Tyr Glu Ala
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Phe Ser Lys Asn Leu Lys Leu Gly Ile His Glu Asp Ser Gln Asn Arg
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Ala Lys Leu Ala Asp Leu Leu Arg Tyr His Ser Thr Lys Ser Gly Asp
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Glu Met Thr Ser Leu Lys Asp Tyr Val Thr Arg Met Lys Glu Gly Gln
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Lys Asp Ile Tyr Tyr Ile Thr Gly Glu Ser Lys Lys Ala Val Glu Asn
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Ser Pro Phe Leu Glu Arg Leu Lys Lys Lys Gly Tyr Glu Val Leu Tyr
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Met Val Asp Ala Ile Asp Glu Tyr Ala Val Gly Gln Leu Lys Glu Tyr
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Asp Gly Lys Lys Leu Val Ser Ala Thr Lys Glu Gly Leu Lys Leu Asp
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Asp Asp Ser Glu Glu Glu Lys Lys Lys Lys Glu Glu Lys Lys Lys Ser
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Phe Glu Asn Leu Cys Lys Ile Ile Lys Asp Ile Leu Gly Asp Arg Val
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Glu Lys Val Val Val Ser Asp Arg Ile Val Asp Ser Pro Cys Cys Leu
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Val Thr Gly Glu Tyr Gly Trp Thr Ala Asn Met Glu Arg Ile Met Lys
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Ala Gln Ala Leu Arg Asp Ser Ser Met Ser Ser Tyr Met Ser Ser Lys
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Lys Arg Ala Glu Ala Asp Lys Asn Asp Lys Ser Val Lys Asp Leu Val
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Leu Leu Leu Phe Glu Thr Ala Leu Leu Thr Ser Gly Phe Ser Leu Asp
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Asp Pro Asn Thr Phe Ala Ala Arg Ile His Arg Met Leu Lys Leu Gly
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Leu Ser Ile Asp Glu Glu Glu Glu Ala Val Glu Asp Ala Asp Met Pro
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Ala Leu Glu Glu Thr Gly Glu Glu Ser Lys Met Glu Glu Val Asp
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