邵天玉 劉思竹 謝維欣 劉興龍 李志勇 王克勤 朱朝東 劉丹
摘要 ?姬小蜂科寄生蜂在農(nóng)業(yè)害蟲防治應(yīng)用中起著非常重要的作用,但因體型小種類多,鑒定較難,導(dǎo)致開發(fā)利用的局限性。隨著分子生物學(xué)的快速發(fā)展,通過(guò)形態(tài)學(xué)與分子生物學(xué)相結(jié)合的方法來(lái)研究小蜂總科已經(jīng)成為發(fā)展趨勢(shì)。利用黑龍江省的6個(gè)吸蟲塔收集到了238個(gè)姬小蜂科樣本。在DNA提取之前通過(guò)形態(tài)學(xué)鑒定為14屬52種。對(duì)其中60個(gè)COI和68個(gè)28S基因進(jìn)行了擴(kuò)增和測(cè)序,并將基因登錄號(hào)提交GenBank;COI基因的登錄號(hào)為MG836426~MG836501,28S基因的登錄號(hào)為MH169011~MH169101。經(jīng)進(jìn)一步計(jì)算COI和28S基因的種內(nèi)和種間遺傳距離發(fā)現(xiàn),COI基因的種間遺傳距離差異顯著,最小種間遺傳距離(6.00%)遠(yuǎn)大于最大種內(nèi)遺傳距離(3.02%)。但是,28S基因的差異較大,許多屬的種內(nèi)遺傳距離超過(guò)種間遺傳距離,重疊現(xiàn)象嚴(yán)重。用MEGA-7.0軟件進(jìn)一步分析了COI基因的序列相似性和系統(tǒng)發(fā)育關(guān)系,結(jié)果表明:COI基因序列的聚類結(jié)果與形態(tài)學(xué)分類基本一致,而28S基因序列的聚類結(jié)果與形態(tài)學(xué)結(jié)果有較大差異??梢?jiàn)COI基因在姬小蜂科的分類鑒定和系統(tǒng)發(fā)育分析上比28S基因有很大優(yōu)勢(shì),更適合姬小蜂科DNA條形碼分析。
關(guān)鍵詞 ?DNA條形碼;COI;28S;分子鑒定;姬小蜂科
中圖分類號(hào) ?S 433 ??文獻(xiàn)標(biāo)識(shí)碼 ?A ??文章編號(hào) ?0517-6611(2023)05-0078-07
doi: 10.3969/j.issn.0517-6611.2023.05.020
開放科學(xué)(資源服務(wù))標(biāo)識(shí)碼(OSID):
Application and Analysis of DNA Bar Code Technology in Species Identification of Eulophidae in Heilongjiang Province
SHAO Tian-yu1, LIU Si-zhu1, XIE Wei-xin2 et al
(1.Chongqing University of Posts and Telecommunications, Chongqing 400065;2.Institute of Intelligent System and Bioinformatics, College of Intelligent Systems Science and Engineering, Harbin Engineering University, Harbin, Heilongjiang 150001)
Abstract ?The Eulophidae parasitoids play a key role in the control of agricultural insects, but because of the small size and many species, identification is difficult, which leads to the limitation of development and utilization. With the rapid development of molecular biology, it’s been quite regular to combine molecular approaches in studying the superfamily Chalcidoidea. In this study, 238 specimens of the family Eulophidae were collected from 6 suction traps in Heilongjiang Province, China. Before DNA extraction, 52 species of 14 genera were identified by morphology. 60 COI and 68 28S genes were amplified and sequenced, which were submitted to GenBank, with accession numbers from MG836426 to MG836501 for COI and from MH169011 to MH169101 for 28S. Intraspecific and interspecific genetic distances were calculated for both COI and 28S genes. The interspecific distances of COI gene was significantly different, with the minimum interspecies genetic distance (6.00%) greater than the maximum intraspecific genetic distance (3.02%), which indicates a clear barcoding gap between species. However, as 28S is highly variable, the intraspecific genetic distances of many genera exceed the interspecific, the overlap phenomenon is obvious. Futher, sequence similarity and phylogenetic relationship were analyzed by MEGA 7.0 software, indicating that the clustering results of COI gene sequences are basically consistent with morphological classification, but that of 28S gene sequences are quite different from those of morphological results. COI gene has some advantages over the conservative 28S gene in the taxonomic identification and phylogenetic resolution of the family Eulophidae, which could be more suitable for DNA barcoding wasps.
Key words ?DNA barcoding;COI;28S;Molecular identification; Eulophidae
寄生性天敵的正確鑒定對(duì)生物防治的高效實(shí)施至關(guān)重要。姬小蜂科昆蟲是世界公認(rèn)的生物防治的主要寄生蜂之一。但是,由于個(gè)體小、種類多、形體多樣、鑒定困難,導(dǎo)致了開發(fā)利用的局限性。在傳統(tǒng)分類鑒定上,要想識(shí)別來(lái)自某個(gè)地區(qū)或某個(gè)項(xiàng)目的姬小蜂科昆蟲,需要專業(yè)領(lǐng)域的、甚至是從事昆蟲分類的專家學(xué)者才能實(shí)現(xiàn)。但由于傳統(tǒng)分類的形態(tài)學(xué)人工鑒定效率很低,已無(wú)法滿足當(dāng)前生物防治快速發(fā)展和大規(guī)模識(shí)別工作的需求。
DNA條形碼已被廣泛應(yīng)用于識(shí)別全球的生物物種,也逐漸被認(rèn)為是行之有效的通用分類方法[1-6]。
該研究將收集到的姬小蜂科樣本,通過(guò)基于線粒體COI 和28S基因的DNA條形碼技術(shù),與NCBI(https://www.ncbi.nlm.nih.gov/genbank/)系統(tǒng)進(jìn)行比對(duì)鑒定,測(cè)試物種鑒定的成功率。此外,通過(guò)計(jì)算COI和28S基因種內(nèi)和種間遺傳距離,檢驗(yàn)了DNA條形碼技術(shù)在姬小蜂科昆蟲鑒定中的準(zhǔn)確性。建立了黑龍江地區(qū)姬小蜂科DNA條形碼數(shù)據(jù)庫(kù),補(bǔ)充了姬小蜂科寄生性天敵物理種的地理資源信息。
1 材料與方法
1.1 樣本取樣
利用黑龍江省的6個(gè)吸蟲塔收集了238個(gè)姬小蜂科樣本,均保存于無(wú)水乙醇中。采樣位置、種類名稱和GenBank登錄號(hào)的詳細(xì)信息見(jiàn)圖1和表1。在DNA提取之前,依據(jù)形態(tài)學(xué)鑒定為14屬52種[7-20]。所有標(biāo)本存放在黑龍江省農(nóng)業(yè)科學(xué)院植物保護(hù)研究所。
1.2 DNA提取、擴(kuò)增和測(cè)序
使用QIAGEN DNeasy提取試劑盒提取基因組DNA。COI基因使用LA Taq(TAKARA)擴(kuò)增, 28S使用MightyAmp(TAKARA)擴(kuò)增。COI基因使用條形碼引物L(fēng)CO1490(5′-GGTCA ACAATCAATCAAATTGG-3′) 和HCO2198(5′-TAAACTTCAGGTGACCAAAAATCA-3′)進(jìn)行擴(kuò)增。28S基因使用條形碼引物D2-3549F(5′-AGTCGTGTTGTGTGTGCAG-3′)和D2-4068R(5′-TTGGTCGTTTCAAGC-GGG-3′)進(jìn)行擴(kuò)增。所有擴(kuò)增反應(yīng)均采用50 μL的PCR體系。COI反應(yīng)體系:5.0 μL 10×LA緩沖液、5.0 μL MgCl2(2.5 mmol/L)、5.0 μL dNTP(2.5 mmol/L)、1.0 μL正反向引物(10 mmol/L)、0.5 μL LA Taq聚合酶(5 U/μL)、2.0~4.0 μL模板DNA和蒸餾水,最終PCR體系補(bǔ)充為50 μL。28S反應(yīng)體系:25.0 μL Mightymp緩沖液、2.1 μL mightyMP DNA聚合酶(1.25 U/μL),正反向引物1.0 μL(10 mmol/L),2.0~4.0 μL模板DNA和蒸餾水,最終PCR體系補(bǔ)充為50 μL。COI PCR反應(yīng)條件為94 ℃預(yù)變性2 min,35個(gè)循環(huán)包括:94 ℃30 s,48~50 ℃50 s,72 ℃延伸1 min,72 ℃延伸10 min。28S PCR反應(yīng)條件為98 ℃預(yù)變性2 min,35個(gè)循環(huán)包括:98 ℃10 s,58 ℃15 s,68 ℃延伸1 min,68 ℃延伸5 min。用ABI3130測(cè)序儀進(jìn)行測(cè)序。
1.3 序列比對(duì)與分子分析
將測(cè)序結(jié)果導(dǎo)入DNAStar中的SeqMan軟件[21],進(jìn)行序列的拼接與手工校正,確定分析的序列,利用NCBI中的“BLAST”軟件進(jìn)行相似性檢索,確定序列方向及目的片段;將確定的序列以及GenBank下載相應(yīng)序列載入Clustal X 1.83 軟件[22] 進(jìn)行序列比對(duì),輸出格式為FASTA。比對(duì)結(jié)果導(dǎo)入MEGA 7.0 軟件[23],計(jì)算各物種間的遺傳距離,轉(zhuǎn)換和顛換值及其比值(R值),保守位點(diǎn)(conserved sites,C)及變異位點(diǎn)(variable sites,V)等數(shù)值。
采用MEGA 7.0軟件統(tǒng)計(jì)序列堿基組成、GC含量、多態(tài)位點(diǎn)和簡(jiǎn)約信息位點(diǎn)等參數(shù);利用Kimura 2-parameter(K2-P)雙參數(shù)模型計(jì)算群體內(nèi)和群體間遺傳距離;以廣赤眼蜂Trichogramma evanescens Westwood(Trichogrammatidae)作為外群,采用鄰接法(neighbor-joining,NJ)構(gòu)建系統(tǒng)發(fā)育進(jìn)化樹。
2 結(jié)果與分析
2.1 NCBI系統(tǒng)的識(shí)別結(jié)果
該研究獲得了60個(gè)625 bp的COI序列和68個(gè)620 bp的28S序列。所有DNA序列均已提交給GenBank,登錄號(hào)分別為MG836426~MG836501和MH169011~MH169101。
根據(jù)COI基因序列,可以直接鑒定出4屬5種,分別為S25P13、HE25P4-1、HE4P30、HE21P1和HE17P2,相似性分別為95%、98%、98%、98%和94%,物種鑒定率為8.3%,按屬分類共鑒定出38個(gè)樣本,占所有樣本的63.3%。此外,共有17個(gè)樣本被錯(cuò)誤識(shí)別,占所有樣本的28.3%。根據(jù)28S基因序列,可以直接鑒定出2屬5種,分別為H26P4、H26P2、HE26P4、H26P3和HE17P2,所有相似性均為99%,物種鑒定率為7.35%。根據(jù)屬分類,共鑒定出51個(gè)樣本,占所有樣本的75.0%。此外,共有12個(gè)樣本被錯(cuò)誤識(shí)別,占所有樣本的17.6%。
2.2 遺傳距離分析
通過(guò)對(duì)黑龍江省姬小蜂科樣本COI和28S基因的遺傳距離分析可知,COI基因的種間平均遺傳距離(15.40%)是種內(nèi)平均遺傳距離(0.60%)的25.67倍,而28S基因的種間平均遺傳距離(64.8%)是種內(nèi)平均遺傳距離(0.27%)的240倍。這完全符合DNA條形碼有效性的標(biāo)準(zhǔn)要求:種間平均遺傳距離至少是種內(nèi)平均遺傳距離的10倍以上[24]。
基于COI基因平均遺傳距離計(jì)算可知,種間種內(nèi)平均遺傳距離差異顯著。最小種間遺傳距離(6.00%)大于最大種內(nèi)遺傳距離(3.02%),不同物種之間沒(méi)有重疊,DNA條形碼顯示出較大的種間距離和較小的種內(nèi)距離,存在明顯的條形碼缺口(圖2)。然而,28S基因是異常多變的。多個(gè)屬的種內(nèi)遺傳距離遠(yuǎn)超過(guò)種間遺傳距離。重疊現(xiàn)象明顯,種內(nèi)和種間物種之間沒(méi)有明顯的“條形碼差異”(圖3)。
2.3 系統(tǒng)發(fā)育分析
經(jīng)計(jì)算可知,COI基因序列中A的平均頻率為30.8%,C、G、T的平均頻率分別為12.7%、13.8%、42.7%。COI基因序列顯示出強(qiáng)烈的腺嘌呤和胸腺嘧啶(AT)偏好,高達(dá)73.5%,這是昆蟲線粒體基因組的典型特征[25-26]。而28S基因序列中A、C、G、T的平均頻率分別為18.5%、27.1%、32.4%、22.0%。
基于COI基因序列的MP系統(tǒng)發(fā)育樹可知,53個(gè)樣本同聚為一個(gè)單系,占88.3%,而該科的所有樣本又同聚集成一個(gè)系,將廣赤眼蜂作為外群,聚類結(jié)果基本符合形態(tài)學(xué)分類(圖4)。然而28S基因序列的聚類結(jié)果與形態(tài)學(xué)分類結(jié)果有較大差異,只有29個(gè)樣本同聚集成一個(gè)單系,占42.7%。28S基因序列的種內(nèi)遺傳距離甚至比種間遺傳距離還大(圖5)。
3 結(jié)論與討論
在該研究中,DNA條形碼在姬小蜂科鑒定中的作用仍然有限。部分樣本只能進(jìn)行屬級(jí)鑒定,物種鑒定必須結(jié)合形態(tài)學(xué)特征。但通過(guò)DNA條形碼的初步鑒定,確實(shí)可以有效地縮小鑒定范圍,大幅減少全部基于形態(tài)學(xué)特征的鑒定和驗(yàn)證所需的精力和時(shí)間,進(jìn)一步確保所有樣品的準(zhǔn)確識(shí)別。
DNA條形碼技術(shù)廣泛應(yīng)用于生態(tài)學(xué)、生物多樣性、檢驗(yàn)檢疫和法醫(yī)鑒定等[27-28],為諸多研究領(lǐng)域都提供了便利。DNA條形碼技術(shù)在生物分類鑒定中發(fā)揮著越來(lái)越重要的作用,是一種快速有效的鑒定工具,逐步得到各研究領(lǐng)域更多學(xué)者的支持[29]。在昆蟲分類學(xué)研究中,DNA條形碼不受樣本條件的限制,對(duì)受試者的形態(tài)完整性更沒(méi)有嚴(yán)格要求,可以大量且同時(shí)進(jìn)行,大大簡(jiǎn)化了物種鑒定過(guò)程[30-31]。然而,?DNA條形碼不能完全取代形態(tài)學(xué)分類,對(duì)于部分昆蟲分類,它僅可以作為形態(tài)學(xué)鑒定的輔助工具,為傳統(tǒng)形態(tài)學(xué)分類提供分子基礎(chǔ)[32]。因此,筆者將形態(tài)分類學(xué)和分子分類學(xué)相結(jié)合,對(duì)黑龍江省姬小蜂科的種類進(jìn)行研究,大大提高了種類鑒定結(jié)果科學(xué)性和準(zhǔn)確性。
研究報(bào)道,COI基因序列的平均種間遺傳距離小于28S基因序列是由于28S基因的進(jìn)化速度相對(duì)較慢,種間高度保守,更適合屬間的系統(tǒng)發(fā)育分析[33]。COI基因系單親遺傳,沒(méi)有重組,而且進(jìn)化速度相對(duì)較快[1],種內(nèi)遺傳變異比28S基因相對(duì)較低,物種特異性較高,更適合分析物種、亞種和近緣物種[34]。與該研究中,COI基因序列比28S基因序列構(gòu)建的系統(tǒng)發(fā)育樹更接近于傳統(tǒng)的形態(tài)分類,COI基因序列更適合用于姬小蜂科的分子鑒定、系統(tǒng)發(fā)育和DNA條形碼標(biāo)記的結(jié)論相互印證。
隨著分子測(cè)序技術(shù)的發(fā)展,高通量測(cè)序技術(shù)已被應(yīng)用于獲取DNA條形碼序列,從而有可能識(shí)別大量物種[35-36]。希望增加基因數(shù)量可以構(gòu)建更精確的系統(tǒng)發(fā)育樹[37],而多個(gè)基因的組合可以在系統(tǒng)分析中提供更有效的系統(tǒng)發(fā)育信息[38-39]?;诙嗷蚱谓M合的DNA條形碼識(shí)別系統(tǒng)將成為一種探索性的趨勢(shì),未來(lái)的DNA條形碼分析研究將朝著多基因、多方法、多學(xué)科組合的方向發(fā)展,只有通過(guò)有效的序列分析才能獲得科學(xué)準(zhǔn)確的結(jié)果。
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