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中国三省松口蘑遗传多样性分析



全 文 :食用菌学报2012.19(1):17~21
收稿日期:2011-10-18原稿;2012-01-16修改稿
基金项目:科技基础性工作专项(编号:2006FY110705)的部分研究内容
作者简介:马银鹏(1987-),男,中国农业科学院在读硕士,主要从事大型真菌研究。
*本文通讯作者 E-mail:sdhcy@yahoo.com.cn
文章编号:1005-9873(2012)01-0017-05
中国三省松口蘑遗传多样性分析
马银鹏,陈 强,赵梦然,邬向丽,张金霞,黄晨阳*
(中国农业科学院农业资源与农业区划研究所,农业部农业微生物资源收集与保藏重点实验室,北京100081)
摘 要:采用ITS、mt SSU rDNA的V4和V9区对采自西藏、吉林和云南3个省份30个地区的59个样本进
行物种鉴定,并运用IGS1-RFLP和 RAPD 进行遗传多样性分析。结果表明:所有样本均为松口蘑
(Tricholoma matsutake),松口蘑ITS序列存在明显的地域性;IGS1-RFLP分析表明,吉林样本属于 A型,西
藏和云南样本是2种新类型;聚类分析表明,在相似系数为0.702水平时将供试样本分为3大类群;我国松口
蘑具有丰富的遗传多样性,并且自然种群遗传多样性地域性明显。
关键词:松口蘑;mt SSU;IGS1-RFLP;RAPD;遗传多样性;地理分布
  松口蘑(Tricholoma matsutake)是重要的可
食用菌根真菌,具有较高的经济价值,广受消费
者欢迎[1]。目前松口蘑尚未实现人工栽培。由
于松口蘑宿主被线虫感染和人类砍伐导致天然
森林减少等原因,松口蘑产量逐年下降[2]。商业
的需求对松口蘑自然种群造成巨大的威胁,在中
国松口蘑被列为二级濒危保护物种。国内外学
者纷纷对松口蘑进行研究,以期对野生资源进行
有效保护与合理利用。
口蘑属(Tricholoma)有70多个种[3],在形
态上,容 易 混 淆;另 外,松 口 蘑 宿 主 有 栲 属
(Castanopsis)、栎属(Quercus)等阔叶树[4];赤松
(Pinus densiflora)、黑松(P.thunbergii)和偃松
(P.pumila)等针叶树[5],这也给形态学物种鉴
定带来不便。随着分子生物学的发展,ITS序列
分析[6]和线粒体小亚基核糖体 DNA(mt SSU
rDNA)V4和V9序列分析[7]成为物种鉴定的常
用方法。
遗传多样性研究是进行资源保护和利用的
前提。国内外学者已采用高度重复序列marY1
和 marY2N [8,9]、IGS1-RFLP [10-12]、SSR [13]、
RAPD [14]和SRAP [15]等多种分子标记对松口蘑
自然种群的遗传多样性进行研究。IGS1-RFLP
可产生 A、B、C、D、E、F、G、H 等8种图谱类型,
且与 地 域 性 显 著 相 关[10-12]。采 用 SSR [13]、
RAPD[14]和SRAP [15]研究发现松口蘑遗传多样
性与地理来源和宿主相关,地理距离较近的样本
遗传距离较近,宿主相同的样本聚集在一起。
在中国,松口蘑主要分布在黑龙江、吉林、四
川、甘肃、贵州、云南、西藏等地[16]。目前,仅见对
云南松口蘑遗传多样性的研究报道[12],尚未见西
藏、吉林松口蘑自然种群遗传多样性研究。本研
究以2010年8月在西藏、吉林和云南三省30个
地区采集的59份松口蘑为材料,应用ITS和 mt
SSU rDNA V4和V9进行物种鉴定,应用IGS1-
RFLP和RAPD研究松口蘑自然种群的遗传多
样性。
1 材料与方法
1.1 供试材料
  供试样本59份,其中1~23来自西藏、24~
32来自吉林、33~59来自云南(表1)。西藏和吉
林样本为鲜品,云南样本为干品。西藏和云南样
本宿主是阔叶树,而吉林样本宿主是针叶树。样
本采集同一地点只采集一个子实体为样本。
1.2 引物
  rDNA ITS区扩增引物为ITS1和ITS4 [6]。
V4和V9区扩增引物分别为 V4UA2/V4RA2和
V9U2/V9R2 [17]。IGS1 区 扩 增 引 物 为 5SA/
CNL12[18]。RAPD分析使用的5个引物分别是:
L02(TGGGCGTCAA)、L03(CCAGCAGCTT)、
L05(ACGCAGGCAC)、L17(AGCCTGAGCC)和
DOI:10.16488/j.cnki.1005-9873.2012.01.008
食 用 菌 学 报 第19卷
表1 供试材料
Table 1 Designation and origin of T.matsutake strains
序号No. 样品名称Strain designation 采集地点 Origin
1~7 波密1~7Bomi 1~7 波密县 Bomi County
8~9 小山1~2Xiaoshan 1~2 林芝县八一镇 Bayi,Linzhi County
10~12 大柏树1~3Dabaishu 1~3 林芝县八一镇 Bayi,Linzhi County
13~16 巴河桥1~4Baheqiao 1~4 工布江达县巴河镇 Bahe,Gongbujiangda County
17~23 米林1~7Milin 1~7 米林县 Milin County
24~26 安图1~3Antu 1~3 安图县 Antu County
27~29 春兴1~3Chunxing 1~3 延吉市依兰镇 Yilan,Yanji City
30~32 智新1~3Zhixin 1~3 龙井市智新镇 Zhixin,Longjing City
33 中甸1Zhongdian 1 香格里拉县格咱乡 Gezan,Shangri-la County
34~36 中甸2~4Zhongdian 2~4 香格里拉县建塘镇Jiantang,Shangri-la County
37 中甸5Zhongdian 5 香格里拉县格咱乡Gezan,Shangri-la County
38 中甸6Zhongdian 6 香格里拉县洛吉乡 Luoji,Shangri-la County
39~40 中甸7~8Zhongdian 7~8 香格里拉县格咱乡 Gezan,Shangri-la County
41 中甸9Zhongdian 9 香格里拉县五境乡 Wujing,Shangri-la County
42 中甸10Zhongdian 10 香格里拉县建塘镇Jiantang,Shangri-la County
43 中甸11Zhongdian 11 香格里拉县尼西乡 Nixi,Shangri-la County
44 中甸-12Zhongdian 12 香格里拉县格咱乡 Gezan,Shangri-la County
45 中甸13Zhongdian 13 德钦县奔子栏乡 Benzilan,Deqin County
46 中甸14Zhongdian 14 香格里拉县建塘镇Jiantang,Shangri-la County
47 中甸15Zhongdian 15 香格里拉县洛吉乡 Luoji,Shangri-la County
48 中甸16Zhongdian 16 香格里拉县尼西乡 Nixi,Shangri-la County
49 中甸17Zhongdian 17 德钦县拖顶乡 Tuoding,Deqin County
50~51 中甸18~19Zhongdian 18~19 香格里拉县小中甸镇 Xiaozhongdian,Shangri-la County
52 Bc-127 宾川县鸡足山镇Jizushan,Binchuan County
53 L1066 剑川县沙溪镇Shaxi,Jianchuan County
54~55 L1123、L1199 洱源县乔后镇 Qiaohou,Eryuan County
56~57 五街1~2Wujie 1~2 南华县五街乡 Wujie,Nanhua County
58~59 祥云1~2Xiangyun 1~2 祥云县东山乡 Dongshan,Xiangyun County
L20(TGGTGGACCA)。引物由北京六合华大基
因科技股份有限公司合成。
1.3DNA提取
  分别取0.5g子实体,采用植物基因组DNA
提取试剂盒(DP305-03,天根生化科技有限公司)
提取DNA。用1.0%琼脂糖凝胶电泳检测DNA
质量,-20℃保存备用。
1.4PCR扩增
  ITS、V4、V9和IGS1反应体系:5μL10×Ex
Taq Buffer (Takara, 大 连),4 μL dNTP
(0.2 mmol/L),引物各 2μL(0.4μmol/L),
1.25 U/μL DNA 聚合酶(Takara),1μL 模板
DNA(约20 ng DNA),ddH2O补至50μL。反应
程序:94℃预变性5 min;94℃变性30 s,42~
55℃复性30 s,72℃延伸30 s,35个循环;72℃
延伸7 min,1.0%琼脂糖凝胶电泳检测。
RAPD反应体系:2μL10×Ex Taq Buffer
(Takara),2μL dNTP(0.2 mmol/L),1μL引物
(0.4 μmol/L),0.5 U/μL DNA 聚 合 酶
(Takara),1μL模板 DNA,ddH2O补至20μL。
反应程序:94℃预变性5 min;94℃变性1 min,
37℃复性1 min,72℃延伸2 min,35个循环;
72℃延伸7 min,1.0%琼脂糖凝胶电泳分析。
1.5PCR产物测序
  ITS、V4、V9和IGS1的PCR产物双向直接
测序,直接测序异常的采用克隆后测序,委托北京
六合华大基因科技股份有限公司进行。PCR产
物 经 UNIQ-10 柱 式 DNA 胶 回 收 试 剂 盒
(Sangon)纯化,纯化后连接于pGEM-T Vector
(Takara),纯化和克隆按试剂盒说明书操作。
1.6IGS1-RFLP分析
   用 Cfr13I限制性内切酶 (New England
Biolabs,北京)酶切IGS1扩增产物。酶切反应体
系:1μL限制性内切酶Cfr13I(5 U/μL),1μL10×
NE buffer 4,5μL扩增产物,ddH2O补至10μL。
37 ℃ 温育 4 h。10% 聚丙烯酰胺凝胶电泳
81
书第1期 马银鹏,等:中国三省松口蘑遗传多样性分析
(PAGE)分析。
1.7 数据处理与分析
  用BLAST对ITS测序结果进行相似性比对
分析。用BioEdit 7.0.9人工核对和剪切测序结
果。用 DNAMAN(Version 5.2.2,Lynnon
Biosoft,魁北克,加拿大)比对ITS、V4、V9和
IGS1序列。“1”代表存在,“0”代表不存在,统计
RAPD条带,利用NTsys_2.02软件进行分析,计
算样品之间的遗传相似系数,用 UPGMA法进行
聚类分析得到聚类树状图。
2 结果与分析
2.1ITS鉴定结果
  测序结果表明3个省份样本的ITS大小相同,
与GenBank(EU294302)中松口蘑ITS序列相似度
为99%~100%,所有样本均为松口蘑;不同省份间
样本存在碱基差异,具有明显的地域性。在474bp
碱基处,吉林所有样本出现C/T的套峰,而云南和
西藏样本此处为T;西藏所有样本在563bp处都为
G,而云南和吉林样本此处为A。
2.2mt SSU rDNA V4和V9区鉴定结果
  对所有样本分析表明,mt SSU rDNA V4区
大小均为225bp,序列完全一致,与GenBank中
松口蘑AF465617.1的V4区完全相同。所有样
本 V9 区大小为 270bp,序列完全一 致,与
AF465617.1的 V9区相比相似度为98%,在
144bp处存在碱基差异,在39、147、154、157bp
处分别存在1个碱基缺失。
2.3IGS1-RFLP分析和IGS1序列分析结果
  对59 个松口蘑的IGS1的 PCR 产物经
Cfr13I酶切,PAGE检测结果表明,所有样本均
产生4条条带。利用DNAMAN对IGS1序列进
行分析,结果表明:所有菌株存在3个Cfr13I识
别位点。IGS1-RFLP后产生的电泳条带实际大
小如下:吉林样本产生215、133、63、45bp 4条条
带;西藏样本产生215、138、63、45bp 4条条带;
云南样本产生219、133、63、45bp 4条条带。按
照GUERIN-LAGUETTE等[10]的划分,吉林样
本属于A型,西藏、云南样本分别具有一特异条
带(138、219bp),为2种新类型。
对3省份的样本分别随机选取5个进行
IGS1测序,结果表明:西藏、吉林、云南IGS1序列
大小分别为461、456、460bp。IGS1序列存在明
显的地域性,同一省份内的样本序列完全相同,省
份间的样本存在差异。与另外两个地区样本相
比,云南样本在302bp处有4个碱基插入,西藏
样本在378bp处有5个碱基插入。吉林与云南
和西藏样本相似度分别为0.991和0.989,云南
和西藏样本相似度为0.981。
2.4 基于RAPD分析结果构建树状图
  5条引物共产生43条条带,其中36条具有
多态性,多态性比例为83.7%。UPGMA聚类结
果见图1。在相似系数为0.702处将供试样本分
为三大类群,西藏样本的最小相似系数为0.720,
图1 松口蘑基于RAPD分析的UPGMA聚类树状图
Fig.1 UPGMA cluster diagram of T.matsutake based on RAPD
91
食 用 菌 学 报 第19卷
云南样本的最小相似系数为0.740,吉林样本的
最小相似系数为0.804。结果表明:我国松口蘑
具有丰富的遗传多样性,西藏和云南松口蘑的遗
传多样性比吉林的高。松口蘑自然种群遗传多
样性的地域性明显。宿主同为阔叶树的西藏和
云南的样品与宿主是针叶树的吉林样品相比,关
系更为相近。
3 讨论
  ITS是真菌分子分类鉴定的首选标记[19]。
本试验研究表明,吉林的松口蘑样品的ITS存在
套峰现象。HUANG等[20]研究表明,在白灵侧
耳(Pleurotus nebrodensis)中ITS存在套峰的原
因是两个细胞核的ITS存在差异。所以,推测本
研究中松口蘑的细胞核的ITS存在差异,这将制
约ITS直接测序法用于松口蘑物种鉴定。mt
SSU rDNA的 V4和 V9区在种内是高度保守
的,在种间不保守,MOUHAMADOU 等[7]研究
认为V4和V9可作为口蘑属DNA条形码。本
研究结果表明,所有样本的mt SSU rDNA V4区
与 GenBank中松口蘑 AF465617.1完全一致。
V9区与 AF465617.1相似度为98%。所以,与
V9区相比,V4区更适合用于松口蘑物种鉴定。
IGS1-RFLP克服了成本高和对测序公司的
依赖性等缺点,是研究遗传多样性的常用方法之
一。本研究表明,酶切产物采用PAGE检测,未
能将三省样本区分开;而用Cfr13I酶切位点分
析IGS1测序结果,发现西藏、吉林、云南三地的
样本酶切条带存在差异。所以,IGS1-RFLP酶切
产物需采用高分辨率的检测方法。
本研究结果表明,松口蘑ITS和IGS1序列
存在明显的地域性。在同一省份内样本ITS和
IGS1序列完全一致,不同省份间存在差异。因此
可利用ITS或IGS1序列的特异位点判别松口蘑
地理来源。吉林所有样本在474bp处出现C/T
的套峰,而云南和西藏样本此处为 T,这个位点
能否作为辨别宿主是阔叶树或针叶树标记,需要
更多的样品验证。
与GUERIN-LAGUETTE等[10]对日本松口蘑
的研究结果相比,西藏和云南的松口蘑产生A~H
等8种图谱之外的新类型。SHA等[12]研究显示
云南松口蘑属于 A型。通过对SHA等[12]报道
IGS序列(DQ323058)比较发现,IGS1-RFLP的
结果应该是219、133、63、45bp 4条条带,并不是
GUERIN-LAGUETTE等[10]报道的A型。
本研究结果表明:我国拥有特有的松口蘑种
质,并具有丰富的遗传多样性。
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[18]HENRION B,LE TACON F,MARTIN F.Rapid
identification of genetic variation of ectomycorrhizal
fungi by amplification of ribosomal RNA genes[J].
New Phytol,1992,122:289-298.
[19]BROCK PM,DORING H,BIDARTONDO MI.
How to know unknown fungi:the role of a
herbarium[J].New Phytol,2009,181(3):719-724.
[20]HUANG CY,XU JY,GAO W,et al.A reason for
overlap peaks in direct sequencing of rRNA gene ITS
in Pleurotus nebrodensis[J].FEMS Microbiol Lett,
2010,305(1):14-17.
[本文编辑] 王瑞霞
12
ACTA EDULIS FUNGI2012.19(1):22~26
Received:Oct.18,2011; Accepted:Jan.16,2012
Supported by the Special Foundation on Scientific and Technological Basic Work,Ministry of Science and Technology
*Corresponding author.Tel:+86-10-82108692 E-mail:sdhcy@yahoo.com.cn
犌犲狀犲狋犻犮犇犻狏犲狉狊犻狋狔狅犳犆犺犻狀犲狊犲犜狉犻犮犺狅犾狅犿犪犿犪狋狊狌狋犪犽犲
犛狋狉犪犻狀狊犳狉狅犿犜犻犫犲狋,犑犻犾犻狀犪狀犱犢狌狀狀犪狀犘狉狅狏犻狀犮犲狊
MA Yinpeng,CHEN Qiang,ZHAO Mengran,WU Xiangli,
ZHANG Jinxia,HUANG Chenyang*
(Institute of Agricultural Resources and Regional Planning,Chinese Academy of Agricultural Sciences;
Key Laboratory of Microbial Resources,Ministry of Agriculture,Beijing 100081,China)
Abstract:Fifty nine mushroom samples were colected from 30locations in Tibet,Jilin and Yunnan and
identified as Tricholoma matsutake based on ITS sequences,and the V4and V9domains of the mitochondrial
smal-subunit(SSU).IGS1markers were region-specific in that samples from a single province had the same
sequence,whereas these sequences differed from the IGS1sequences of samples originating from the other
two provinces.Abundant genetic diversity among T.matsutake strains in China was revealed by RAPD
analysis.Mushroom samples from Jilin corresponded to the previously designated type A,whereas two new
types were observed among samples from Tibet and Yunnan.UPGMA-based clustering separated the 59test
strains into three groups at an overal similarity coefficient of 0.702.
Key words:Tricholoma matsutake;mt SSU;IGS1-RFLP;RAPD;genetic diversity;geographical distribution
  Tricholoma matsutakeis an important edible
mycorrhizal fungus of high economic value,the
taste and texture of which is widely appreciated
by consumers
[1].At present,artificial cultivation
of T.matsutake has not been realized,and
continuing consumer demand poses an enormous
threat to the natural mushroom populations.
Annual harvests from the wild have decreased
markedly in recent years due to deforestation and
other human activities[2],and T.matsutake is
now classified as a Grade 2endangered species in
China.Consequently,research on T.matsutake
by both domestic and foreign scholars is currently
focused on protecting and making better use of
this valuable resource.
The genus Tricholoma comprises more
than 70species[3]that are not always readily
recognized from the appearance of the
mushroom fruit bodies.Host plants include
both broadleaf trees (Castanopsis spp.,
Quercus spp.)and conifers(Pinus densiflora,
P.thunbergii,P.pumila)which also adds to
the difficulty of identifying species based on
morphology.However,with the development
of molecular  biological  techniques, ITS
sequences,and the V4and V9domains of the
mitochondrial SSU,can be used for species
identification.
Understanding the genetic diversity of a
particular resource is a prerequisite for its
effective protection and utilization. Both
Chinese and foreign researchers have studied
the genetic diversity among natural populations
of T.matsutake using the highly repetitive
sequences marY1 and marY2N [8,9],and
various molecular markers including IGS1-
RFLP[10-12],SSR [13],RAPD [14]and SRAP[15].
Eight distinct IGS1 rDNA types,A,B,C,D,
E,F,G and H,were identified using the
restriction endonuclease Cfr13I[10],and the
distribution of the various types was often
associated  with  different  geographical
locations.SSR[13], RAPD[14] and SRAP[15]
revealed that genetic diversity in T.matsutake
No.1 MA Yinpeng,CHEN Qiang,ZHAO Mengran,et al
was related to geographic origin and plant
host.Thus,strains growing within a smaler
geographical area exhibited closer genetic
affinity,as did strains associated with a given
host species.
In China, T. matsutake is mainly
distributed in Heilongjiang,Jilin,Sichuan,
Gansu, Guizhou, Yunnan and Tibet[16].
Although research data relating to the genetic
diversity of T.matsutake in Yunnan have been
reported[12],little is known about the natural
populations from Tibet and Jilin.In this study,
59 T.matsutake samples were colected from
30 locations in Tibet,Jilin and Yunnan,and
their identity confirmed using ITS sequences,
and the V4 and V9 domains of SSU.Genetic
diversity among the strains was analyzed using
IGS1-RFLP and RAPD.
1 Materials and Methods
1.1 Materials
  A total of 59 T.matsutake strains were
colected from Tibet(1-23),Jilin(24-32)and
Yunnan(33-59)in China(see Table 1in the
Chinese version).Samples from Tibet and Jilin
were fresh mushroom fruit bodies while those
from Yunnan were dry sporophores.Samples
from Tibet and Yunnan were associated with
broad-leaf trees,while those from Jilin were
associated with conifer hosts.Only one fruit
body was colected from each sampling site.
1.2Primers
  Primers used for PCR amplification were as
folows:ITS1and ITS4(rDNA ITS region)[6];
V4UA2/V4RA2and V9U2/V9R2(V4and V9
domains, respectively )[17]; 5SA/CNL12
(IGS1)[18]; L02 (TGGGCGTCAA), L03
(CCAGCAGCTT),L05 (ACGCAGGC-AC),
L17 (AGCCTGAGCC) and L20 (TGG-
TGGACCA)(RAPD).Primers were synthe-
sized by Beijing Liuhe Huada Gene Corporation
(BGI),Beijing,China.
1.3Extraction of DNA
   DNA was extracted from T.matsutake
fruit body samples(0.5g)using the extraction
kit DP305-03(Tiangen Biochemical Science and
Technology Co.Ltd,Beijing,China)according
to the manufacturer’s instructions and stored at
- 20 ℃. DNA quality was assessed by
electrophoresis on 1% (w/v)agarose gels.
1.4PCR amplification
  ITS、V4、V9and IGS1amplification was
carried out in 50 μL reaction mixtures
containing:5μL 10×Ex Taq Buffer,4μL
dNTP(0.2 mmol/L),2μL primers(0.4μmol/L)
1.25 U Taq DNA polymerase,1μL template
DNA (20 ng DNA),and ddH2O to volume.
Amplification conditions were as folows:1
cycle at 94℃for 5 min,35 cycles at 94℃for
30 s,42~55 ℃ for 30 s,72 ℃ for 30 s;
folowed by a final extension at 72 ℃ for
7 min.
RAPD amplification was carried out in
20μL reaction mixtures containing:2μL10×
Ex Taq Buffer,2μL dNTP(0.2 mmol/L),
1μL primer(0.4μmol/L),0.5 U Taq DNA
polymerase(Takara),and 1μL template DNA
(20 ng).Amplification conditions were as
folows:1 cycle at 94℃for 5 min;35 cycles at
94℃for 1 min,37 ℃for 1 min,72 ℃ for
2 min;folowed by a final extension at 72 ℃
for 7 min.
Amplification products were detected by
electrophoresis on 1% (w/v)agarose gels.
1.5Sequencing of PCR products
  PCR amplified ITS regions、V4and V9
domains,and IGS1markers were subjected to
bidirectional sequencing either directly (BGI)
or,if abnormalities were detected, after
cloning.PCR products were purified using the
UNIQ-10type DNA gel extraction kit(Sangon,
Shanghai, China), ligated  to  pGEM-T
(Takara),purified and cloned according to the
manufacturer’s instructions.
1.6IGS1-RFLP analysis
  IGS1amplification products were digested
for 4 h at 37 ℃ using Cfr13Irestriction
32
ACTA EDULIS FUNGI  Vol.19
endonuclease(New England Biolabs,Beijing,
China).Reaction mixtures contained:1 μL
restriction endonuclease,1μL10× NE buffer
4,5μL amplification product,and ddH2O to
10μL volume.Digests were analyzed by PAGE
using 10% (w/v)polyacrylamide gels.
1.7Data analysis
  Similarity analysis of ITS sequencing data
was carried out using BLAST.ITS、V4、V9and
IGS1sequences were aligned using DNAMAN
(Version 5.2.2,Lynnon Biosoft,Quebec,
Canada).RAPD bands were analyzed using
NTsys_2.02software,and genetic similarity
coefficients between samples were calculated.
Cluster analysis was carried out using the
UPGMA method.
2 Results and Analysis
2.1ITS sequence analysis
    Al the samples were confirmed as T.
matsutake.Sequencing data showed that the ITS
markers of the samples colected from al three
provinces were of the same size,and exhibited
99-100% sequence similarity with the T.
matsutake ITS sequence deposited in GenBank
(EU294302).Base differences were recorded in
samples from the different provinces;for
example,at position 474,al the samples from
Jilin had overlapping C/T peaks whereas
samples from Yunnan and Tibet had a T
residue.At position 563,al the samples from
Tibet had a G residue,while the position in
samples from Yunnan and Jilin was occupied
by A.
2.2V4and V9domains of SSU
  The V4domain of al the test samples
consisted of 225 bp,and the sequence was
identical to the V4domain of T.matsutake SSU
deposited  in  GenBank (Accession  No.
AF465617.1).The V9domain of al the test
samples consisted of 270bp,and exhibited a
98%sequence similarity with the V9domain of
SSU of T.matsutake deposited in GenBank
(Accession No. AF465617.1). A base
difference was detected at position 144and bases
were missing in the V9 domain of the test
samples at positions 39,147,154and 157.
2.3IGS1-RFLP and IGS1sequence analysis
   Sequence analysis revealed three Cfr13I
recognition sites in the IGS1region of al the
strains.Thus,PAGE of Cfr13Idigests of IGS1
amplification products generated from the 59 T.
matsutake samples revealed four bands in every
case.Actual IGS1-RFLP band sizes were as
folows:Jilin(215,133,63and 45bp),Tibet
(215,138,63and 45bp)and Yunnan (219,
133,63 and 45 bp).Samples from Jilin
corresponded to type A as designated in Ref.10,
whereas two new types,consisting of 138bp
and 219bp,were observed in samples from
Tibet and Yunnan,respectively.
IGS1sequencing results obtained from five
samples randomly selected from each of the
three provinces showed that the sequences of
IGS1in the samples from Tibet,Jilin and
Yunnan consisted of 461,456and 460bp,
respectively.IGS1 sequences were region-
specific:i.e.whereas samples from the same
province had the same sequence,these were
different to the sequences of samples from the
other two provinces.Four base insertions at
position 302 were recorded in T.matsutake
samples from Yunnan,and five base insertions
at position 378 in T. matsutake samples
colected in Tibet.Sample similarity values
were 0.991(Jilin and Yunnan),0.989 (Jilin
and Tibet)and 0.981(Yunnan and Tibet).
2.4Cluster diagram of T.matsutake strains
based on RAPD
  The five RAPD primers used in this study
generated 43 different bands,of which 36
(83.7%)were polymorphic.UPGMA-based
clustering separated the test strains into three
groups at a similarity coefficient of 0.702
(Figure 1,see the Chinese version).The
minimal similarity coefficients for the samples
from Tibet,Yunnan and Jilin were 0.720,
42
No.1 MA Yinpeng,CHEN Qiang,ZHAO Mengran,et al
0.740 and 0.804,respectively. Our data
revealed a rich genetic diversity among natural
populations of T.matsutakein China.Regional
features were also evident in that the genetic
diversity among T.matsutake populations from
Tibet and Yunnan was higher compared with
those originating from Jilin.Samples colected
in Tibet and Yunnan,where the host plants
were broad-leaf trees,exhibited a closer genetic
relationship  compared  with  the  conifer-
associated Jilin strains.
3 Discussion
  ITS sequences are the preferred molecular
markers for identifying and classifying fungi[19].
However,our data revealed sets of overlapping
peaks in the ITS sequences of T.matsutake
specimens from Jilin that necessitated a cloning
step prior to effective sequencing.Previously,
HUANGet al[20]reported that failure to directly
sequence ITS regions of Pleurotus nebrodensis
was due to base pair insertion/deletion
differences between the two nuclei of that
fungus,leading us to speculate that similar
differences apply to the nuclei of T.matsutake.
The V4and V9domains of the SSU are highly
conserved inter-specificaly but not intra-
specificaly and,according to MOUHAMADOU
et al[7],could serve as a DNA barcode for
Tricholomaand other basidiomycetes.Our data
showed that the sequence of the V4domain in al
the samples examined in this study was identical
to the V4 domain of T. matsutake SSU
deposited  in  GenBank (Accession  No.
AF465617.1).This makes the V4domain more
suitable for identification of T. matsutake
compared with the V9region since there was
only a 98%similarity between the V9sequences
of the test samples and the V9domain of T.
matsutake  SSU  deposited  in  GenBank
(Accession No.AF465617.1).
The IGS1-RFLP method is more cost-
effective and reduces the dependence on
sequencing companies,and is widely used in
genetic diversity studies.Although the band
patterns observed by PAGE alone failed to
distinguish between samples colected from the
three provinces,clear differences were evident
after treatment with the Cfr13I restriction
enzyme and high-resolution detection of the
IGS1-RFLP digestion products.
Our data demonstrated that the ITS and
IGS1sequences of T.matsutake strains exhibit
distinctive regional features. Although these
sequences were identical in samples colected from
sites within the same province,sequences in
samples colected in one province differed from the
sequences recorded in samples from another
province.For example,at position 474of IGS1,
al the samples from Jilin had overlapping C/T
peaks whereas samples from Yunnan and Tibet
had a T residue.Therefore,it may be possible to
identify the geographical origin of a strain based
on specific sites within the ITS or IGS1
sequences. Further research is required to
determine if it is possible to use ITS and/or IGS1
sequences to identify the host plant as a broad-leaf
tree or a conifer.
Samples from Jilin corresponded to type A
as designated in Ref.10,whereas two new
types,consisting of 138bp and 219bp,were
observed in samples from Tibet and Yunnan,
respectively.Cfr13Idigests of IGS1in T.
matsutake strains from Tibet and Yunnan
revealed a sequence different from types A-H
mapped by GUERIN-LAGUETTE et al[10]and
T.matsutake from Japan. SHA et al[12]
reported that T.matsutake strains from Yunnan
belonged to type A, but based on our
interpretation of the IGS sequence(DQ323058),
and the four fragments(219,133,63,45bp)
generated by Cfr13Idigestion,this is incorrect.
In conclusion,our data reported here reveal
the existence of unique T.matsutake germplasm
resources in China,which exhibit abundant
genetic diversity.
52
ACTA EDULIS FUNGI  Vol.19
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62