全 文 :书食用菌学报2012.19(4):1~6
收稿日期:2012-10-15原稿;2012-11-15修改稿
基金项目:上海市科委重点科技攻关项目(编号:10391900900)、种业发展专项[编号:沪农科种字(2012)第6号]的
部分研究内容
作者简介:张 丹(1986-),男,2011年毕业于扬州大学农学院,硕士,研究实习员,主要从事食用菌遗传育种研究。
*本文通讯作者 E-mail:xdshang@163.com
文章编号:1005-9873(2012)04-0001-06
基于香菇全基因组序列开发的部分
SSR标记多态性分析与品种鉴定初探
张 丹1,巫 萍1,2,章炉军1,唐利华1,宋春艳1,尚晓冬1!,鲍大鹏1,谭 琦1
(1上海市农业科学院食用菌研究所,农业部南方食用菌资源利用重点实验室,国家食用菌工程技术研究中心,
国家食用菌加工技术研发分中心,上海市农业遗传育种重点开放实验室,上海201403;
2南京农业大学生命科学学院,江苏南京210095)
摘 要:利用香菇(Lentinula edodes)全基因组序列信息开发的35个香菇SSR(simple sequence repeat)分子
标记用于中国25个香菇品种的鉴定。所选SSR标记共检测出174个条带,各引物检测到的条带数量变化范
围为2~12。筛选出的7对SSR引物组合显示了良好的品种特异性鉴定能力,可以有效地鉴定部分国审香菇
品种。
关键词:香菇;全基因组序列;SSR;品种鉴定
简单序列重复(simple sequence repeat,SSR),
又称微卫星DNA,是以2~6个碱基为重复基元的
串联重复序列,广泛存在于高等生物的基因组中。
在众多的分子标记方法中,基于PCR的SSR标记具
有位点特异、共显性、复等位、基因组中分布广泛等
特点,成为构建连锁遗传图谱、研究群体遗传学、绘
制品种指纹图谱、筛选目标性状分子标记及分子标记
辅助育种等的理想工具。在未知基因组序列信息的
情况下,一般可从EST序列[1]或通过构建微卫星文
库[2,3]开发SSR标记。此过程需构建文库并测序,步
骤繁琐、耗时长、开发的标记数量少、难度大、成功率
低[4],限制了SSR技术的普遍应用。与EST-SSR相
比,基于全基因组信息开发的SSR类型更多、多态性
更高、分布更广泛[5]。随着下一代全基因组测序技术
的普及,获得全基因组信息进而开发SSR已经变得十
分快捷,其开发与应用将会越来越多。
香菇(Lentinula edodes)是我国十分重要的
栽培食用菌,近年来栽培地域、季节得到快速拓
展,产量增长较快。香菇栽培的快速发展需要多
品种支撑,目前通过国审的香菇品种已经超过20
个,各地还有许多同种异名或同名异种的品种在
大量使用。为满足不同栽培需求而进行的多品
种配套使用很容易造成菌种混乱,严重时会影响
香菇正常生产甚至绝产,迫切需要快速、准确的
菌种“产前”鉴定方法。基于香菇基因组序列的
SSR标记的开发对于我国香菇资源的遗传结构
分析,分子标记辅助育种,我国主栽香菇品种的
亲缘关系理清具有重要应用价值。
1 材料与方法
1.1菌株
25份香菇(L.edodes)栽培品种和2份野生
菌种作为供试材料(表1)。
1.2SSR引物开发与合成
香菇L135菌株2个原生质体单核体135A、
135B及其转色阶段的转录组交由深圳华大基因
科技有限公司进行测序,测序采用solexa和454
相 结 合 的 方 法,测 序 深 度 为 6 倍。 用
SSRhunter1.3软件[6]对香菇基因组中SSR的总
数、分布、motif类型等信息进行了分析。利用
primer premier 5.0[7]软件,设计了108对SSR引
物,委托生工生物工程(上海)有限公司合成。
1.3SSR引物扩增片段多态性初步分析
选用香菇栽培菌株L808、香九及另外2株野
生菌株 HN10Le317、HN10Le318的DNA为模
板,对合成的108对SSR引物进行预扩增。将预
扩增筛选得到的SSR引物对25株栽培品种和2
株野生菌株进行扩增试验。
DOI:10.16488/j.cnki.1005-9873.2012.04.007
食 用 菌 学 报 第19卷
1.4香菇栽培品种鉴定
初选25个国审认定的香菇品种作为供试材
料(表1),利用基于香菇全基因组序列开发的条
带清晰的SSR标记对香菇品种进行特异性鉴定。
根据所有SSR标记的基因型扩增结果,筛选出
SSR标记,构建SSR标记指纹图谱。
1.5DNA提取
将供试菌株菌丝接种至PDA液体培养基,
表1 供试香菇栽培品种来源
Table 1 Sources of L.edodes test strains
编号
No.
菌株
Strain
系谱来源
Pedigree
品种来源
Source
1 申香8号Shen-8 70×苏香Suxiang
2 申香10号Shen-10 26×苏香Suxiang
3 申香12号Shen-12 69×苏香Suxiang
上海Shanghai
4 Cr02 7402×Lc-01
5 L135
国外引进品种筛选育成
Derived from an overseas strain by systematic breeding
6 闵丰1号 Minfeng-1 L12×L34
7 Cr62 7917×L21
8 Cr04 7917×L21
福建省
Fujian Province
9
庆元9015
Qingyuan 9015
241、8210、日丰34三个菌株经组织分离筛选育成。
Derivedfrom strains 241,8210and Rifeng 34
by systematic breeding
10 241-4
241菌株筛选育成 Derived from strain 241
by systematic breeding
11 武香1号 Wuxiang-1
国外引进菌种系统选育而成
Derived from an overseas strain by systematic breeding
浙江省
Zhejiang Province
12 赣香1号 Ganxiang-1 1303×HO3
江西省
Jiangxi Province
13 金地香菇Jindi L939×135
四川省
Sichuan Province
14 森源1号Senyuan-1 8404×856
15 森源10号Senyuan-10 8404×135
16 森源8404Senyuan 8404 野生种驯化育成 Domesticated from a wild-type strain
湖北省
Hubei Province
17 香九 Xiang-9 野生种驯化育成 Domesticated from a wild-type strain
18 香杂26Xiangza-26 No.8×No.40
19 广香 Guangxiang 野生菌株驯化育成Domesticated from a wild-type strain
广东省
Guangdong
Province
20 华香8号 Huaxiang-8
栽培品种经分离系统选育而成
Derived from acultivated strain by systematic breeding
21 华香5号 Huaxiang-5
国外引进菌株经分离选育而成
Derived from an overseas strain by systematic breeding
22 L952
国外引进菌株经系统选育而成
Derived from an overseas strain by systematic breeding
湖北省
Hubei Province
23 菌兴8号Junxing-8
野生香菇驯化栽培育成
Domesticated from a wild-type strain
24 L9319
农民菇棚采集种菇分离驯化育成
Derived from a cultivated strain using tissue isolation
25 L808
国外引进菌株经分离选育而成
Derived from an overseas strain by systematic breeding
浙江省
Zhejiang Province
26 HN10Le317 野生种 Wild strain
27 HN10Le318 野生种 Wild strain
湖南省
Hunan Province
2
第4期 张 丹,等:基于香菇全基因组序列开发的部分SSR标记多态性分析与品种鉴定初探
在25℃、140 r/min振荡培养4 d。过滤收集菌
丝,采用CTAB法[8]提取基因组DNA。使用分
光光度计(NANODROP-1000型,美国 Thermo
公司产品)对提取的DNA进行浓度及纯度检测。
将DNA溶液稀释至50 ng/μL,4℃保存备用。
1.6SSR基因型鉴定
PCR扩增体系为:总体积20μL,包括:10×
PCR 缓冲液 2μL,25 mmol/L MgCl2 2μL,
10 mmol/L dNTP0.4μL,5 U/μL Taq DNA酶
0.2μL,10μmol/L SSR标记正向引物和反向引
物体积各1.5μL,浓度20~30 ng/μL提取的
DNA模板2μL,ddH2O10.4μL。PCR反应程
序为:94℃5 min;94℃50 s,55℃50 s,72℃
50 s,30个循环;72℃保持5 min。
1.7凝胶电泳及数据分析
PCR扩增反应完成后,将12μL1×加样缓
冲液加入20μL PCR扩增产物中混匀,于95℃
变性 5 min,结束后置于冰水混合物中冷却
3 min,点样3μL于6%变性聚丙烯酰胺凝胶上
电泳,电泳缓冲液为1×TBE,电压1000 v,电流
200 mA,功率200 W,电泳45 min,银染,显色,
拍照,分析结果。
2 结果与分析
2.1香菇基因组测序及SSR引物
从香菇 135 菌株的 2 个单核体基因组
scalfold数据和转录组unigene数据中,分别搜索
到2889、2972和5007个SSR位点(1~6碱基重
复,12bp以上)。其中3碱基重复所占比例最
高,超过54%,其次为单碱基,超过24%(图1)。
在3 碱基重 复 中,AGG/CCT、AAG/CTT 和
ATC/GAT是丰度最高的重复基元(图2)。
图1 香菇135菌株单核体和转录组的SSR标记分布
Fig.1 Distribution of SSRs in monokaryons and the transcriptome of L.edodes 135
图2 香菇135菌株单核体和转录组的motif类型次数分布
Fig.2 Distribution of SSR motifs in monokaryons and the transcriptome of L.edodes 135
3
食 用 菌 学 报 第19卷
2.2SSR引物多态性
选用香菇栽培菌株L808、香九及另外2株野
生菌株 HN10Le317、HN10Le318的DNA为模
板预扩增结果表明,有79对引物得到扩增产物,
其余29对引物未得到扩增产物。将预扩增筛选
得到的79对SSR引物对25株栽培品种和2株
野生菌株进行扩增试验,发现其中74对引物表
现出多态性,大多数标记为单拷贝引物,少数为
多拷贝位点引物。
2.3香菇栽培品种多位点SSR指纹图谱
利用35对基于香菇全基因组序列开发的条
带清晰的SSR标记对香菇品种进行特异性鉴定
(图3)。所选SSR标记共检测出了35个多态性
位点、174个等位变异,各位点检测到的等位片段
数量变化范围为2~12。根据所有SSR标记的
基因型扩增结果,筛选出7对SSR标记,构建了
一套SSR标记指纹图谱。所选7对引物(表2)扩
增的DNA片段均具有重复性好、带型清晰、等位
片段大小容易区分的特点,目前这7对引物可以
鉴定出4份香菇栽培品种的特异性(图4)。
泳道数字同表1菌株编号 Numbers as listed in Table 1
图3 引物192-1在25份国审香菇栽培品种上的扩增带型
Fig.3 Polymorphic bands generated from 25 L.edodes strains by primer 192-1
泳道 M:分子量标记;泳道1~7:7对SSR引物;泳道NC:空白对照
Lane M:marker;lanes 1-7:SSR markers;Lane NC:control
图4 香菇菌种Cr02、L135、闵丰1号和L808的7种SSR引物扩增结果
Fig.4 Fingerprint profiles of Cr02,L135,Minfeng-1,L808constructed by 7SSR markers
4
第4期 张 丹,等:基于香菇全基因组序列开发的部分SSR标记多态性分析与品种鉴定初探
表2 构建指纹图谱的7对SSR引物序列信息表
Table 2 Sequence information of seven SSR primers used for constructing fingerprint profiles
引物序号
Primer number
重复片段序列
Repeat sequence
正向/反向引物(5’→3’)
Forward/reverse primers(5’→3’)
1 (GATG)5 AACAACCCAAATGAAGCCAG/AACTCTCTGAGCTTCGCTGC
2
(TGC)5tgaagttgttgg
tggagttgttgt(TGC)6
GGTATACCGTTCATTTGCGG/ACCCAATTTCAGCTCCCTTT
3 (TTC)7 CGGTGACGATTTTTGAGGTT/GAGGGGaAGAAAAAGCAAGC
4 (TATC)5 CTAGTGGGACCCCGTCTGTA/TGGTTGAAGTGCCTCACAAG
5 (GGAA)5 ACCTTCATCAATCGCTCCAC/TCCAAAACCCTTTTAGCTGC
6 (TATC)5 GCTTTTGGGACCACATCTTC/ATGTGCCGTTTTCAAATTCC
7 (AGGT)5 CCCAAAAAGGATTTCAGCAA/AACCGGAGTGGTGTAAGTGC
3 讨论
与其它类型的分子标记相比,单个SSR位点
所能检测到的等位变异的数目是最高的,尤其是
基于全基因组信息开发的SSR具有更高的多态
性。且在一定长度范围内,SSR的长度与其多态
性呈正相关关系[1,9]。与 XIAO等[10]基于 EST
开发的SSR引物进行了比较,发现他们的SSR引
物在25份栽培菌株中的多态性很低,24对引物
中,只检测到8个多态性标记,其SSR等位片段
变化范围为2~6。相对于EST开发的SSR,基
于基因组信息所开发的SSR显示出量大、基因组
覆盖面广、多态性高的优点。
SSR分子标记用于品种鉴定具有操作简单、
结果准确的特点,已经用于作物的DUS鉴定[11]
和双 孢 蘑 菇 (Agaricus bisporus)[12]、黑 木 耳
(Auricularia auricula)[13]及糙皮侧耳(Pleurotus
ostreatus)[4]的品种鉴定。香菇中SSR的信息已
经受到研究者关注[14,15],并有用于香菇野生资源
遗传多态性研究的报道[10]。由于目前我国香菇
栽培品种较少,区别这些品种所需要的SSR位点
并不需要很多,随着品种的增加,本研究开发的其
它SSR位点将随时为新品种的鉴别提供信息。
本研究发现的香菇SSR位点,显示出良好的多态
性,对于理清我国主栽香菇品种的亲缘关系具有
重要应用价值。
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6
ACTA EDULIS FUNGI2012.19(4):7~10
Received:Oct.15,2012; Accepted:Nov.15,2012
Supported by the Shanghai Science and Technology Office (10391900900)and Foundation of Seed Industry
Development(2012-6SAAS)
*Corresponding author. E-mail:xdshang@163.com
Polymorphism of SSR Markers Based on the Whole
Genome Sequence of Lentinula edodes
and Use in Strain Identification
ZHANG Dan1,WU Ping1,2,ZHANG Lujun1,TANG Lihua1,SONG Chunyan1
SHANG Xiaodong1*,BAO Dapeng1,TAN Qi 1
(1Institute of Edible Fungi,Shanghai Academy of Agricultural Sciences,Key Laboratory of Edible Fungi Resources
and Utilization(South),Ministry of Agriculture,P.R.China;National Engineering Research Center of Edible Fungi,
National R&D Center for Edible Fungi Processing,Key Laboratory of Agricultural Genetics and Breeding of Shanghai,
Shanghai 201403,China:2 Colege of Life Sciences,Nanjing Agricultural University,Nanjing,Jiangsu 210095,China)
Abstract:Thirty-five simple sequence repeat(SSR)molecular markers based on the whole genome sequence of
Lentinula edodes were shown to differentiate 25cultivated strains of the mushroom certified by the Chinese
state.Polymorphic loci,represented by 174distinct bands,were detected using 35primer pairs,and the
number of fragments amplified by each of these primer pairs ranged from 2to 12.SSR fingerprints,
constructed using seven primer pairs (selected on the basis of band separation and reproducibility),
differentiated four L.edodes strains(Cr02,L135,Minfeng-1and L808).
Key words:Lentinula edodes;whole genome sequence;single sequence repeat(SSR);strain differentiation
Simple sequence repeats (SSRs),also
known as microsatelites, are repeating
sequences of 2~6base pairs of DNA widely
found in higher biological genomes.Compared
with other molecular markers, SSRs are
currently preferable due to their genome-wide
distribution,hypervariability,co-dominance,
specificity and reproducibility.SSR markers
have been widely used to build linkage maps,
for studying population genetics, finger-
printing, and molecular marker-assisted
breeding.
SSR markers include expressed sequence
tag (EST)-derived sequences[1]and genomic
SSR markers used to construct microsatelite
libraries[2-4]. Compared with the former,
genomic SSR markers exhibit greater variabi-
lity,a higher degree of polymorphism,and are
distributed more widely throughout the
genome[5].With further improvements in the
technology associated with next generation
whole-genome sequencing,the development
and application of genomic SSR markers wil
increase in importance.
Lentinula edodes is an important cultivated
mushroom in China.Output has increased
steadily in recent years due to both an
expansion in the area used for cultivation and
in the length of the cultivation season.This
rapid development has led to a demand for
more varieties of the mushroom,and more
than 20varieties are currently under large-scale
cultivation throughout the country.However,
considerable confusion has arisen due to the
assignment of either different designations to
identical varieties or the same designation to
different varieties.Moreover,the extent of
multi-variety cultivation,adopted in order to
ACTA EDULIS FUNGI Vol.19
meet different requirements, has led to
problems in terms of spawn authenticity that
has often adversely affected normal production
and even led to zero yields.Consequently,
there is an urgent need to develop rapid and
accurate methods for the precise identification
of commercial strains of L. edodes.
Therefore,we have developed SSR markers
based on the whole genome sequence of L.
edodes, which have important application
value for analyzing genetic structure,molecular
marker-assisted breeding,and in revealing
genetic relationships between the main
cultivated varieties.
1 Materials and Methods
1.1Strains
Twenty-five L. edodes commercial
cultivars and two wild strains were obtained
from several sources throughout China (see
Table 1in the Chinese version).
1.2SSR primers
The genomes of two protoplast
monokaryons,135Aand 135B (derived from
strain L135),and the transcriptome of strain
L135,were sequenced using the combined
Solexa and 454 methods(6times sequencing
depth)by the Shenzhen Genomics Institute.
The total number of SSRs,distribution and
motif type were determined with SSR Hunter
1.3software[6].A total of 108SSR primer
pairs were designed using Primer Premier 5.0
software[7]and were synthesized by Sangon
(Shanghai)Co.,Ltd.
1.3Polymorphism of the fragments amplified by
the SSR primers
Initialy,108SSR primer pairs were used to
amplify DNA from four randomly selected
strains (L808, xiangjiu, HN10Le317 and
HN10Le318),from which 79primer pairs were
then selected for amplifying DNA from 25
cultivars and two wild-type strains.
1.4Species identification
Twenty-five L.edodes strains were
identified by SSR markers developed from the
whole genome sequence,and SSR fingerprints
were constructed based on the amplification
data.
1.5DNA extraction
Potato dextrose (PD) medium was
inoculated with mycelium from a Potato
Dextrose Agar(PDA)stock slant and incubated
at 25 ℃ for 4d with shaking (140r/min).
Fungal mycelium was colected by filtration
and genomic DNA was extracted using the
cetyltrimethylammonium bromide (CTAB)
method[8].The concentration and purity of the
extracted DNA were determined spectrophoto-
metricaly at 260/280 nm (Nanodrop-1000
type,Thermo Company,USA)folowed by
storage at-70℃.Immediately prior to use,
the DNA solution was diluted to 50ng/μL.
1.6Genotype identification using SSRs
Amplification was carried out in 20μL
reaction mixtures containing:2 μL 10 ×
reaction buffer,2μL MgCl2 (25 mmol/L),
0.4μL dNTP (10 mmol/L),0.2 μL Taq
polymerase 5 U/μL,2 μL template DNA
(50ng/μL),1.5μL+1.5μL forward and
reverse primers(10μmol/L)and ddH2O to
volume.
SSR amplification conditions were as
folows:1cycle at 94℃for 5min;30cycles at
94℃for 50s,55℃for 50s,and 72℃for
50s,folowed by a final extension at 72℃for
5min.
1.7Gel electrophoresis anddata analysis
Amplification products (20 μL )was
mixed with 12μL 1×loading buffer,incubated
at 95℃for 5min,and then placed in an ice-
water mixture for 3min.Aliquots(3μL)were
subjected to electrophoresis for 45min on 6%
(v/v)acrylamide gels (1000 V,200 mA,
200W)and,after staining with silver nitrate,
the amplification patterns were determined by
visual examination.
2 Results and Analysis
2.1Genome sequencing and SSR primers
8
No.4 ZHANG Dan,WU Ping,ZHANG Lujun,et al
Totaly,2889,2972and 5007SSR loci(1~
6bp repeats,fragment length >12bp)were
detected from the data obtained from the single
nuclear genome scaffolds of monokaryons 135A
and 135B,and the transcriptome of strain 135,
respectively.The proportion of trinucleotide
repeats was highest (>54%),folowed by
mononucleotide repeats(more than 24%)(see
Fig.1in the Chinese version).AGG/CCT,
AAG/CTT and ATC/GAT were the most
abundant motifs among the trinucleotide
repeats(see Fig.2in the Chinese version).
2.2SSR primer polymorphism
Preliminary screening of 108primer pairs
revealed that only 79 of these generated
amplification products. Polymorphism was
observed in products generated by 74primer
pairs.Most primer pairs amplified only one
type of SSR marker while others amplified
multiple types.
2.3SSR fingerprinting
Twenty-five L.edodes strains were
differentiated by 35SSR markers based on the
whole genome sequence (see Fig.3in the
Chinese version).Polymorphic loci,represented
by 174distinct bands,were detected using 35
primer pairs,and the number of fragments
amplified by each of these primer pairs ranged
from 2to 12.SSR fingerprints,constructed
using seven primer pairs(selected on the basis
of band separation and reproducibility),
differentiated four L.edodes strains(Cr02,
L135,Minfeng-1and L808)(see Fig.2in the
Chinese version).
3 Discussion
SSR loci,especialy SSRs based on the
whole genome sequence,can detect more alelic
variation compared with other molecular
markers,and a positive correlation exists
between the degree of polymorphism and the
length of the product amplified by the SSR
primer pairs[1,9]. Conversely, EST-derived
SSRs exhibited very low polymorphism.We
identified only eight polymorphic markers,
each consisting of 2to 6fragments,from 25
L.edodes cultivars using 24 primer pairs
originaly developed for amplification of EST-
derived SSRs by XIAOet al
[10].
SSR molecular markers have been used for
crop DUS testing
[11],and to differentiate
strains of Agaricus bisporus[12],Auricularia
auricula [13]and Pleurotus ostreatus[4].SSR
markers have also been described from
L.edodes[14,15]and used to evaluate genetic
diversity within wild-type strains of this
mushroom[10]. Although relatively few
commercial cultivars are currently used in
China,the continuing development of new
varieties wil require accurate methods of
identification and certification. In this
context,SSR markers appear to have important
potential application value.
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