楊春玲,陳慧芳,彭敏,李強(qiáng)勇,曾地剛,劉青云,趙永貞,陳曉漢,陳秀荔
摘要:【目的】篩選出凡納濱對(duì)蝦生長(zhǎng)發(fā)育的功能基因及代謝調(diào)控網(wǎng)絡(luò),揭示其生長(zhǎng)發(fā)育的分子機(jī)制,為后續(xù)開展凡納濱對(duì)蝦分子生物學(xué)研究提供寶貴的基因數(shù)據(jù)來源?!痉椒ā恳钥焖偕L(zhǎng)群體和慢速生長(zhǎng)群體的凡納濱對(duì)蝦肌肉組織為研究材料,通過Illumina HiSeqTM2500平臺(tái)對(duì)構(gòu)建的cDNA文庫進(jìn)行高通量測(cè)序分析,以StringTie進(jìn)行拼接組裝后利用DESeq2篩選差異表達(dá)基因,并基于KOG、GO、nr、COG、Swiss-Pro、KEGG和Pfam等數(shù)據(jù)庫進(jìn)行差異表達(dá)基因功能注釋分析。【結(jié)果】經(jīng)拼接組裝共獲得53458844條Clean reads,各樣品Clean reads的Q30均在93.00%以上;Illumina測(cè)序獲得的Clean reads與參考基因組的比對(duì)效率在87.75%~87.80%,說明轉(zhuǎn)錄組測(cè)序數(shù)據(jù)真實(shí)可靠。采用SnpEff進(jìn)行SNP/InDel變異注釋分析,結(jié)果顯示,SNP位點(diǎn)中以A>G、G>A、C>T和T>C等4種類型的數(shù)量較多(14950~21562個(gè)),InDel位點(diǎn)則以SYNONYMOUS_CODING的數(shù)量最多(33630個(gè))。使用StringTie對(duì)Mapped reads(比對(duì)到參考基因組的Reads)進(jìn)行拼接,共發(fā)掘到4607個(gè)新基因,分別輸入COG、GO、KEGG、KOG、Pfam、Swiss-Prot、eggNOG和nr數(shù)據(jù)庫中進(jìn)行序列比對(duì),最終發(fā)現(xiàn)共有1098個(gè)新基因被注釋,以被nr數(shù)據(jù)庫注釋的新基因數(shù)量最多(1077個(gè)),而被COG數(shù)據(jù)庫注釋的新基因數(shù)量最少(416個(gè))?;赒-value<0.05且Fold Change>2的篩選條件,共獲得1408個(gè)差異表達(dá)基因(661個(gè)為顯著上調(diào)表達(dá)基因,747個(gè)為顯著下調(diào)表達(dá)基因);1408個(gè)差異表達(dá)基因被注釋到53個(gè)GO功能條目中,其中,22條被注釋到生物學(xué)過程(Biological process),16條被注釋到細(xì)胞組分(Cellular component),15條被注釋到分子功能(Molecular function);KEGG信號(hào)通路富集分析發(fā)現(xiàn)3條重要的信號(hào)通路,分別是溶酶體通路(Lysosome)、氨基糖和核苷酸糖新陳代謝(Amino sugar and nucleotide sugar metabolism)及鞘脂類代謝(Sphingolipid metabolism)。在溶酶體通路中,CTSL基因、Nramp基因、MyoG基因和Myf5基因在凡納濱對(duì)蝦快速生長(zhǎng)群體肌肉組織中呈上調(diào)表達(dá),而Trypsin基因呈下調(diào)表達(dá)?!窘Y(jié)論】通過轉(zhuǎn)錄組測(cè)序分析從快速生長(zhǎng)群體和慢速生長(zhǎng)群體的凡納濱對(duì)蝦肌肉組織中篩選出1408個(gè)差異表達(dá)基因(661個(gè)為顯著上調(diào)表達(dá)基因,747個(gè)為顯著下調(diào)表達(dá)基因),主要富集在溶酶體、氨基糖和核苷酸糖新陳代謝及鞘脂類代謝等通路上,在對(duì)蝦肌肉生長(zhǎng)發(fā)育過程中發(fā)揮重要作用。
關(guān)鍵詞: 凡納濱對(duì)蝦;差異表達(dá)基因;肌肉;生長(zhǎng)發(fā)育;轉(zhuǎn)錄組測(cè)序
中圖分類號(hào): S945.49? ? ? ? ? ? ? ? ? ? ? ? ?文獻(xiàn)標(biāo)志碼: A 文章編號(hào):2095-1191(2021)09-2319-10
Transcriptome sequencing and screening of genes related to muscle growth and development in Litopenaeus vannamei
YANG Chun-ling1, CHEN Hui-fang2, PENG Min1, LI Qiang-yong1, ZENG Di-gang1,
LIU Qing-yun1, ZHAO Yong-zhen1, CHEN Xiao-han1, CHEN Xiu-li1*
(1Guangxi Academy of Fishery Sciences/Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Nanning? 530021, China; 2College of Animal Science and Technology, Guangxi University, Nanning? 530004, China)
Abstract:【Objective】To screen out the functional genes and metabolic regulation network of growth and development in Litopenaeus vannamei, reveal the molecular mechanism of its growth and development, and provide a valuable source of genetic data for the subsequent molecular biology research of L. vannamei. 【Method】The muscle tissue of the fast-growing group and the slow-growing group of L. vannamei was used as the research material, high-throughput sequencing analysis was performed on the cDNA library through the Illumina HiSeqTM2500 platform, and the DESeq2 was used to screen differentially expressed genes after assembly using StringTie, and the functional annotation of differentially expressed genes was performed based on KOG, GO, nr, COG, Swiss-Pro, KEGG and Pfam databases. 【Result】A total of 53458844 Clean reads with Q30 more than 93.00% were obtained after splicing assembly. The comparison efficiency of Clean reads obtained by Illumina sequencing and the reference genome was 87.75% to 87.80%, indicating that the transcriptome sequencing data were true and reliable. SNPEff was used to annotate SNP and InDel variation, results showed that the number of 4 types of SNP loci, A>G, G>A, C>T, and T>C, was large(14950-21562), and the number of synonymous_coding points of InDel loci was the largest (33630). Using StringTie software to splice Mapped Read (Reads that were aligned to the reference genome), a total of 4607 new genes were discovered. The genes were input into COG, GO, KEGG, KOG, Pfam, Swiss-Prot, eggNOG and nr databases for sequence alignment. Finally, it was found that a total of 1098 new genes were annotated, with the largest number of new genes annotated by the nr database(1077), and the smallest number of new genes annotated by the COG database(416).? Based on the screening conditions of Q-value<0.05 and Fold Change>2, a total of 1408 differential expression genes were detected, in which 661 genes were significantly up-regulated and 747 genes were significantly down-regulated. A total of 1408 differentially expressed genes were annotated to 53 GO function items, in which 22 items were annotated to biological process, 16 items were annotated to cellular component, 15 items were annotated to molecular function. KEGG signal pathway enrichment analysis revealed three important signal pathways, namely lysosome pathway, amino sugar and nucleotide sugar metabolism pathway and sphingolipid metabolism pathway. In the lysosomal pathway, CTSL gene, Nramp gene, MyoG gene and Myf5 gene were up-regulated in the muscle tissue of fast-growing L. vannamei, while Trypsin gene was down-regulated. 【Conclusion】Through transcriptome sequencing analysis, 1408 differentially expressed genes (661 are significantly up-regulated genes and 747 are significantly down-regulated genes) were screened from the muscle tissues of fast-growing and slow-growing L. vannamei, which are mainly enriched in lysosomes, sphingolipid metabolism, amino sugar and nucleotide sugar metabolism pathways. They play an important role in the growth and development of L. vannamei muscle.
Key words: Litopenaeus vannamei; differentially expressed gene; muscles; growth and development; transcriptome sequencing
Foundation item: Guangxi Key Research and Development Project(Guike AB19245032); Guangxi Innovation Team Building Project of National Modern Agricultural Industrial Technology System(nycytxgxcxtd-14-01); Special Project of Modern Agricultural Industrial Technology System Construction(CARS-48)
0 引言
【研究意義】凡納濱對(duì)蝦(Litopenaeus vannamei)又稱南美白對(duì)蝦,隸屬于節(jié)肢動(dòng)物門(Arthropoda)甲殼綱(Crustacea)十足目(Decapoda),具有抗逆性強(qiáng)、適鹽范圍廣、肉質(zhì)鮮美及經(jīng)濟(jì)價(jià)值高等優(yōu)點(diǎn),深受廣大養(yǎng)殖戶的喜愛(錢昭英,2014;彭敏等,2020)。自20世紀(jì)80年代末引進(jìn)凡納濱對(duì)蝦以來,經(jīng)過20多年的發(fā)展,我國已形成自遼寧至廣西沿海的巨大養(yǎng)殖帶,且近年來逐漸推廣到湖南、湖北、江西和新疆等地區(qū),養(yǎng)殖總面積達(dá)25.6萬ha,年總產(chǎn)量達(dá)140萬t,占全球?qū)ξr總產(chǎn)量的1/3以上,產(chǎn)值達(dá)2000多億元,我國已發(fā)展成為凡納濱對(duì)蝦養(yǎng)殖第一大國(滕瑜等,2021)。生長(zhǎng)性狀是對(duì)蝦養(yǎng)殖的最重要經(jīng)濟(jì)性狀,直接影響其養(yǎng)殖經(jīng)濟(jì)效益,而遺傳選育技術(shù)是提高動(dòng)物機(jī)體生長(zhǎng)性能最有效的措施之一。因此,揭示優(yōu)良性狀形成的分子機(jī)理,開展快速生長(zhǎng)品系的分子標(biāo)記輔助選育,是當(dāng)前凡納濱對(duì)蝦遺傳育種領(lǐng)域最重要的研究方向。【前人研究進(jìn)展】在哺乳動(dòng)物中,肌肉發(fā)育調(diào)控是研究機(jī)體生長(zhǎng)發(fā)育規(guī)律最重要的內(nèi)容之一,目前針對(duì)哺乳動(dòng)物肌肉生長(zhǎng)發(fā)育調(diào)控的分子機(jī)理已有深入研究(Buckingham et al.,2003;Carvajal et al.,2010)。肌細(xì)胞的分化與生長(zhǎng)不僅受正、負(fù)決定因子的雙向調(diào)控,還依賴于鋅指蛋白及生長(zhǎng)因子等組織特異因子的微調(diào)控(Buckingham et al.,2003;Carvajal and Rigby,2010),其中以bHLH(Basic-helix-loop-helix)為核心結(jié)構(gòu)域的生肌調(diào)節(jié)因子(Myogenic regulatory factor,MRFs)在肌肉的發(fā)生發(fā)育過程中起正向調(diào)控作用,包括肌分化因子(MyoD)、生肌因子5(Myf5)、肌細(xì)胞生成素(MyoG)和生肌調(diào)節(jié)因子4(MRF4),且在肌肉的發(fā)生發(fā)育過程中具有時(shí)空表達(dá)特異性,其調(diào)控功能各異但又存在功能補(bǔ)償(Pownall et al.,2002;Botzenhart et al.,2019)。肌肉生長(zhǎng)抑制因子(Myostatin)則是肌肉生長(zhǎng)發(fā)育過程中最重要的負(fù)調(diào)控因子(Otto and Patel,2010),在牛(Grobet et al.,1997;Kambadur et al.,1997)和小鼠(McPherron et al.,1997)中缺失或突變可導(dǎo)致其肌肉過度增長(zhǎng);近年來的研究還發(fā)現(xiàn)在牛、羊和狗等動(dòng)物中Myogenin基因突變減弱其活性的同時(shí)對(duì)肌肉發(fā)育產(chǎn)生顯著影響(Aiello et al.,2018)。在對(duì)蝦方面,Lee等(2015)研究表明,dsRNA沉默凡納濱對(duì)蝦肌生長(zhǎng)抑制素基因(LvMstn)表達(dá)后,凡納濱對(duì)蝦的生長(zhǎng)速度變慢;Kong等(2020)通過分析中國對(duì)蝦(Fenneropenaeus chinensis)FcMstn基因表達(dá)與生長(zhǎng)性狀的關(guān)系,發(fā)現(xiàn)FcMstn基因的表達(dá)與中國對(duì)蝦生長(zhǎng)性狀呈負(fù)相關(guān),且雌性個(gè)體的FcMstn基因平均表達(dá)量顯著低于雄性個(gè)體,即FcMstn基因?qū)χ袊鴮?duì)蝦的肌肉生長(zhǎng)呈負(fù)調(diào)控作用;Yan等(2020)也研究證實(shí),F(xiàn)cMstn基因作為負(fù)調(diào)控因子參與肌肉生成過程,通過RNA干擾(RNAi)降低FcMstn基因表達(dá)水平的中國對(duì)蝦顯示出更快的生長(zhǎng)速度?!颈狙芯壳腥朦c(diǎn)】肌肉是對(duì)蝦機(jī)體的主要組成部分,占其體重的60%以上,肌肉生長(zhǎng)發(fā)育程度是決定對(duì)蝦生長(zhǎng)快慢、體形大小和生長(zhǎng)性狀優(yōu)劣的主要因素。在家畜遺傳改良工作中,已有研究通過篩查調(diào)控肌肉發(fā)育基因上的有益突變而選育出生長(zhǎng)性能優(yōu)良的新品種(Smith et al.,2000;Braunschweig,2010),但至今鮮見有關(guān)凡納濱對(duì)蝦肌肉發(fā)育調(diào)控機(jī)理的研究報(bào)道?!緮M解決的關(guān)鍵問題】通過對(duì)凡納濱對(duì)蝦肌肉組織生長(zhǎng)性狀進(jìn)行轉(zhuǎn)錄組測(cè)序分析,對(duì)比相關(guān)基因組序列,篩選出凡納濱對(duì)蝦生長(zhǎng)發(fā)育的功能基因及代謝調(diào)控網(wǎng)絡(luò),進(jìn)一步揭示其生長(zhǎng)發(fā)育的分子機(jī)制,為后續(xù)開展凡納濱對(duì)蝦分子生物學(xué)研究提供寶貴的基因數(shù)據(jù)來源。
1 材料與方法
1. 1 試驗(yàn)材料
供試凡納濱對(duì)蝦由廣西水產(chǎn)科學(xué)研究院南美白對(duì)蝦遺傳育種中心提供。通過對(duì)比凡納濱對(duì)蝦群體的體長(zhǎng)和體重,分別篩選出快速生長(zhǎng)群體30尾、慢速生長(zhǎng)群體30尾,取其肌肉組織,液氮速凍后-80 ℃保存?zhèn)溆谩?/p>
1. 2 試驗(yàn)方法
取適量凡納濱對(duì)蝦肌肉組織樣本,按照RNA提取試劑盒及miRNA Isolation Kit試劑盒說明進(jìn)行總RNA提取和分離,通過Qubit 2.0、NanoDrop及Aglient 2100等對(duì)總RNA的濃度、純度和完整性進(jìn)行檢測(cè)(李隱俠等,2019;楊和川等,2020),取質(zhì)量合格的RNA樣品進(jìn)行mRNA富集,并構(gòu)建cDNA文庫,然后采用Qubit 2.0和Agient 2100檢測(cè)文庫插入片段的長(zhǎng)度及濃度,并以熒光定量PCR準(zhǔn)確定量cDNA文庫的有效濃度,最后在Illumina HiSeqTM 2500平臺(tái)上完成高通量測(cè)序分析。
1. 3 數(shù)據(jù)處理分析
下機(jī)數(shù)據(jù)經(jīng)質(zhì)量評(píng)估和統(tǒng)計(jì)后,獲得高質(zhì)量的測(cè)序序列(Clean reads)。采用HISAT2對(duì)凡納濱對(duì)蝦基因組進(jìn)行比對(duì)分析,將匹配的片段進(jìn)行隨機(jī)性檢驗(yàn)和插入片段長(zhǎng)度評(píng)估;利用StringTie對(duì)比對(duì)上的Clean reads進(jìn)行組裝以獲得更完整的轉(zhuǎn)錄本,然后進(jìn)行新基因發(fā)掘及表達(dá)量、可變剪接和基因結(jié)構(gòu)分析;通過DESeq2分析不同肌肉樣品組織中的基因差異表達(dá),并基于KOG、GO、nr、COG、Swiss-Pro、KEGG和Pfam等數(shù)據(jù)庫進(jìn)行差異表達(dá)基因功能注釋分析。
2 結(jié)果與分析
2. 1 轉(zhuǎn)錄組測(cè)序分析與組裝結(jié)果
cDNA文庫的Illumina測(cè)序數(shù)據(jù)經(jīng)測(cè)序質(zhì)量控制,共獲得53458844條Clean reads(表1),然后與凡納濱對(duì)蝦基因組序列進(jìn)行比對(duì)分析,并利用StringTie對(duì)比對(duì)上的Clean reads進(jìn)行組裝和定量分析,結(jié)果發(fā)現(xiàn)快速生長(zhǎng)群體和慢速生長(zhǎng)群體凡納濱對(duì)蝦肌肉樣品的Clean reads與參考基因組的比對(duì)效率分別為87.75%和87.80%,具有較高的匹配率,基因組G+C含量在49.79%~50.23%,且Q30均高于93.00%,表明Illumina測(cè)序數(shù)據(jù)及參考基因組數(shù)據(jù)真實(shí)可靠,可用于后續(xù)研究。
2. 2 SNP/InDel分析注釋結(jié)果
根據(jù)Illumina測(cè)序獲得的Clean reads與凡納濱對(duì)蝦基因組序列的比對(duì)分析結(jié)果,采用GATK鑒定測(cè)序樣品與參考基因組間的堿基錯(cuò)配情況,以識(shí)別潛在的SNP位點(diǎn),并利用SnpEff分析注釋SNP/InDel變異。統(tǒng)計(jì)每個(gè)樣品SNP位點(diǎn)的數(shù)目、轉(zhuǎn)換類型比例、顛換類型比例及雜合型比例,結(jié)果(圖1)顯示,A>G、G>A、C>T和T>C等4種類型的SNP位點(diǎn)數(shù)量較多(14950~21562個(gè)),而A>C、C>A、A>T、T>A、C>G、G>C、G>T和T>G等8種類型的SNP位點(diǎn)數(shù)量相對(duì)較少(2982~7326個(gè))。同時(shí)統(tǒng)計(jì)每個(gè)樣品InDel位點(diǎn)的數(shù)目和注釋類型,結(jié)果(圖2)發(fā)現(xiàn),各種類型的InDel位點(diǎn)數(shù)量差異明顯,以SYNONYMOUS_CODING的數(shù)量最多(33630個(gè)),其次是INTERGENIC、INTRON、DOWNSTREAM、UTR_3_PRIME和NON_ SYNONYMOUS_CODING等5種類型(8125~15934個(gè)),而INTRAGENIC、UPSTREAM、UTR_5_PRIME、SPLICE_SITE_ACCEPTOR、SPLICE_SITE_DONOR、
SPLICE_SITE_REGION、START_GAINED、START_ LOST、FRAME_SHIFT、CODON_INSERTION、CODON_DELETION、CODON_CHANGE_PLUS_CODON_INSERTION、CODON_CHANGE_PLUS_CODON_DELETION、SYNONYMOUS_CODING、NON_ SYNONYMOUS_CODING、SYNONYMOUS_STOP、 STOP_GAINED和STOP_LOST等類型的數(shù)量較少(4~3207個(gè)),其他類型的InDel位點(diǎn)數(shù)量為16011個(gè)。
2. 3 新基因功能注釋分析結(jié)果
對(duì)匹配基因組的Clean reads進(jìn)行拼接,并搜索參考基因組的注釋信息,然后基于所選參考基因組序列,使用StringTie對(duì)Mapped reads(比對(duì)到參考基因組的Reads)進(jìn)行拼接,并與原有的基因組注釋信息進(jìn)行注釋分析,尋找未被注釋的轉(zhuǎn)錄區(qū),發(fā)掘新轉(zhuǎn)錄本和新基因。過濾掉編碼肽鏈過短(少于50個(gè)氨基酸殘基)或只包含單個(gè)外顯子的序列,共發(fā)掘到4607個(gè)未被注釋的轉(zhuǎn)錄區(qū)(新基因)。將發(fā)掘到的新基因分別輸入COG、GO、KEGG、KOG、Pfam、Swiss-Prot、eggNOG和nr數(shù)據(jù)庫中進(jìn)行序列比對(duì),以獲得新基因的注釋信息。最終發(fā)現(xiàn)共有1098個(gè)新基因被注釋,各數(shù)據(jù)庫注釋的新基因數(shù)量見表2。其中,以被nr數(shù)據(jù)庫注釋的新基因數(shù)量最多(1077個(gè)),而被COG數(shù)據(jù)庫注釋的新基因數(shù)量最少(416個(gè))。
2. 4 差異表達(dá)基因分析結(jié)果
利用DESeq2對(duì)具有生物學(xué)重復(fù)樣本進(jìn)行樣品間的基因差異表達(dá)分析,以獲得表達(dá)基因集;同時(shí)以EBSeq對(duì)沒有生物學(xué)重復(fù)樣本進(jìn)行基因差異表達(dá)分析。對(duì)凡納濱對(duì)蝦快速生長(zhǎng)群體和慢速生長(zhǎng)群體的轉(zhuǎn)錄本進(jìn)行定量分析,設(shè)篩選差異條件為Q-value<0.05且Fold Change>2,共獲得1408個(gè)差異表達(dá)基因,其中,661個(gè)為顯著上調(diào)表達(dá)基因,747個(gè)為顯著下調(diào)表達(dá)基因,二者差異不明顯(圖3)。
2. 4. 1 差異表達(dá)基因GO功能注釋分析結(jié)果 通過對(duì)差異表達(dá)基因進(jìn)行GO功能注釋分析,結(jié)果顯示1408個(gè)差異表達(dá)基因被注釋到53個(gè)GO功能條目中,其中,22條被注釋到生物學(xué)過程(Biological process),16條被注釋到細(xì)胞組分(Cellular component),15條被注釋到分子功能(Molecular function)。由圖4可看出,在生物學(xué)過程分類中,差異表達(dá)基因主要集中在細(xì)胞過程(Cellular process)、代謝過程(Metabolic process)及單一生物過程(Single-organism process)等類別,說明凡納濱對(duì)蝦在生長(zhǎng)過程中有大量參與調(diào)節(jié)代謝活動(dòng)的基因存在;在細(xì)胞組分分類中,差異表達(dá)基因主要集中在細(xì)胞區(qū)域(Cell part)、細(xì)胞(Cell)和細(xì)胞膜(Membrane)等類別,說明細(xì)胞膜及其細(xì)胞組分在凡納濱對(duì)蝦肌肉生長(zhǎng)發(fā)育過程中發(fā)揮重要作用;在分子功能分類中,差異表達(dá)基因主要集中在結(jié)合(Binding)和催化活性(Catalytic activity)等類別,說明各種酶的催化作用在凡納濱對(duì)蝦肌肉生長(zhǎng)發(fā)育過程中發(fā)揮重要作用。
2. 4. 2 差異表達(dá)基因KEGG信號(hào)通路富集分析結(jié)果
在凡納濱對(duì)蝦肌肉組織轉(zhuǎn)錄組測(cè)序中,共有275個(gè)差異表達(dá)基因富集到49條KEGG信號(hào)通路上,可劃分為環(huán)境信息處理(Environmental information processing)、新陳代謝(Metabolism)、遺傳信息處理(Genetic information processing)、細(xì)胞過程(Cellular processes)、有機(jī)系統(tǒng)(Organismal systems)及人類疾?。℉uman diseases)等六大類(圖5)。其中,以新陳代謝的通路最多,有27條KEGG信號(hào)通路,共富集有217個(gè)差異表達(dá)基因,占78.91%;有機(jī)系統(tǒng)和人類疾病的通路最少,均只有1條KEGG信號(hào)通路,分別富集有4個(gè)和6個(gè)差異表達(dá)基因。由圖6可看出,在KEGG信號(hào)通路中富集程度排名前10的通路依次位溶酶體(Lysosome)、氨基糖和核苷酸糖新陳代謝(Amino sugar and nucleotide sugar metabolism)、鞘脂類代謝(Sphingolipid metabolism)、花生四烯酸代謝(Arachidonic acid metabolism)、細(xì)胞色素P450異生物質(zhì)代謝(Matabolism of xenobiotics by cytochrome P450)、淀粉和蔗糖代謝(Starch and sucrose metabolism)、戊糖和葡萄糖醛酸相互轉(zhuǎn)化(Pentose and glucuronate interconversions)、果糖和甘露糖代謝(Fructose and mannose metabolism)、甘氨酸、絲氨酸和蘇氨酸代謝(Glycine,serine and threonine metabolism)及甘油脂代謝(Glycerolipid metabolism)。
2. 5 凡納濱對(duì)蝦生長(zhǎng)相關(guān)基因差異表達(dá)分析結(jié)果
在篩選獲得的差異表達(dá)基因中,天然抗性相關(guān)巨噬蛋白基因(Nramp)、組織蛋白酶L基因(CTSL)、胰蛋白酶基因(Trypsin)、MyoG基因及Myf5基因等已被證實(shí)在動(dòng)物的生長(zhǎng)發(fā)育過程中發(fā)揮重要作用(Pownall et al.,2002;Glenn et al.,2005;Otto and Patel,2010;Peracino et al.,2013)。這5個(gè)基因在快速生長(zhǎng)群體和慢速生長(zhǎng)群體凡納濱對(duì)蝦肌肉組織中的轉(zhuǎn)錄組測(cè)序結(jié)果(表3)顯示,CTSL基因、Nramp基因、MyoG基因和Myf5基因在凡納濱對(duì)蝦快速生長(zhǎng)群體肌肉組織中呈上調(diào)表達(dá),而Trypsin基因在凡納濱對(duì)蝦快速生長(zhǎng)群體肌肉組織中呈下調(diào)表達(dá)。
3 討論
轉(zhuǎn)錄組測(cè)序分析是目前對(duì)動(dòng)植物及微生物進(jìn)行非模式生物研究的常用方法,能有效分析基因在特定條件下的表達(dá)情況,挖掘出生物網(wǎng)絡(luò)調(diào)控及其分子機(jī)制(羅輝等,2015;李敏等,2019;肖韻錚等,2020)。至今,針對(duì)凡納濱對(duì)蝦的轉(zhuǎn)錄組測(cè)序已有較多研究報(bào)道。曾地剛等(2013)采用454高通量測(cè)序技術(shù)對(duì)凡納濱對(duì)蝦肝胰腺的轉(zhuǎn)錄組進(jìn)行測(cè)序,結(jié)果獲得500177條ESTs,經(jīng)拼接后獲得20225個(gè)Unigenes,其長(zhǎng)度范圍為50~8980 bp,平均507 bp。Lu等(2016)選取耐氨氮組和常規(guī)組肝的胰腺組織進(jìn)行轉(zhuǎn)錄組測(cè)序分析,最終組裝獲得78636個(gè)Unigenes,并篩選得到136個(gè)顯著差異表達(dá)基因。董麗君等(2019)以凡納濱對(duì)蝦低溫脅迫組和常溫組肝胰腺組織為材料進(jìn)行轉(zhuǎn)錄組測(cè)序分析,結(jié)果獲得50921個(gè)Unigenes,設(shè)置差異表達(dá)基因篩選閥值為Fold Change>2和Q-value<0.05,最終篩選得到243個(gè)低溫脅迫相關(guān)基因,其中89個(gè)上調(diào)表達(dá)、154個(gè)下調(diào)表達(dá)。為了挖掘和利用凡納濱對(duì)蝦生長(zhǎng)相關(guān)基因資源,本研究對(duì)生長(zhǎng)差異顯著的快速生長(zhǎng)群體和慢速生長(zhǎng)群體肌肉組織樣本進(jìn)行轉(zhuǎn)錄組測(cè)序和生物信息學(xué)分析,Illumina測(cè)序數(shù)據(jù)經(jīng)測(cè)序質(zhì)量控制后共獲得53458844條Clean reads,各樣品Clean reads的Q30均在93.00%以上,證明Illumina測(cè)序數(shù)據(jù)真實(shí)可靠,即轉(zhuǎn)錄組測(cè)序結(jié)果能滿足后續(xù)研究的要求,為凡納濱對(duì)蝦生長(zhǎng)差異基因的篩選打下基礎(chǔ)。
凡納濱對(duì)蝦基因組數(shù)據(jù)已經(jīng)能在互聯(lián)網(wǎng)上檢索獲得,將測(cè)序獲得的數(shù)據(jù)輸入已知數(shù)據(jù)庫中進(jìn)行比對(duì)分析,發(fā)現(xiàn)Illumina測(cè)序獲得的Clean reads與參考基因組的比對(duì)效率在87.75%~87.80%,說明比對(duì)結(jié)果有效,也進(jìn)一步證實(shí)轉(zhuǎn)錄組測(cè)序數(shù)據(jù)和基因組數(shù)據(jù)真實(shí)可靠。根據(jù)比對(duì)結(jié)果,進(jìn)行新基因發(fā)掘、基因結(jié)構(gòu)優(yōu)化分析及可變剪接預(yù)測(cè)分析,共發(fā)掘到4607個(gè)新基因;將這些新基因分別輸入COG、GO、KEGG、KOG、Pfam、Swiss-Prot、eggNOG和nr數(shù)據(jù)庫中進(jìn)行注釋分析,最終發(fā)現(xiàn)共有1098個(gè)新基因被注釋,其中注釋到nr數(shù)據(jù)庫1077個(gè),eggNOG數(shù)據(jù)庫948個(gè),Pfam數(shù)據(jù)庫917個(gè),KOG數(shù)據(jù)庫714個(gè),Swiss-Prot數(shù)據(jù)庫663個(gè),KEGG數(shù)據(jù)庫551個(gè),GO數(shù)據(jù)庫430個(gè),COG數(shù)據(jù)庫416個(gè)。KEGG信號(hào)通路富集分析結(jié)果顯示,有385個(gè)差異表達(dá)基因富集成環(huán)境信息處理、新陳代謝、遺傳信息處理、細(xì)胞過程、有機(jī)系統(tǒng)及人類疾病等六大類。此外,KEGG信號(hào)通路富集分析發(fā)現(xiàn)3條重要的信號(hào)通路,分別是溶酶體、氨基糖和核苷酸糖代謝及鞘脂類代謝。其中,溶酶體主要起消化作用,是細(xì)胞自溶、防御及其對(duì)某些物質(zhì)利用等信號(hào)轉(zhuǎn)導(dǎo)通路的重要共同交匯通路(Lamming and Bar-Peled,2019);氨基糖和核苷酸糖代謝屬于能量代謝通路,影響生物的發(fā)育及其免疫等過程(張陽,2018)。本研究通過對(duì)比快速生長(zhǎng)群體和慢速生長(zhǎng)群體凡納濱對(duì)蝦肌肉組織中的差異表達(dá)基因,發(fā)現(xiàn)以溶酶體通路的富集程度最高,說明其在凡納繽對(duì)蝦肌肉生長(zhǎng)發(fā)育過程中發(fā)揮重要作用。
本研究通過對(duì)快速生長(zhǎng)群體和慢速生長(zhǎng)群體的凡納濱對(duì)蝦肌肉組織進(jìn)行轉(zhuǎn)錄組測(cè)序分析,最終篩選獲得1408個(gè)差異表達(dá)基因,其中,661個(gè)為顯著上調(diào)基因,747個(gè)為顯著下調(diào)基因,為揭示凡納濱對(duì)蝦生長(zhǎng)發(fā)育的分子機(jī)制及開展生長(zhǎng)相關(guān)基因的功能研究打下了基礎(chǔ)。在溶酶體通路中,發(fā)現(xiàn)CTSL基因和Nramp基因在凡納濱對(duì)蝦肌肉中的表達(dá)量存在顯著差異。楊康等(2015)研究發(fā)現(xiàn),在草魚(Liza haematocheila)的生長(zhǎng)過程及免疫反應(yīng)中,Nramp基因在腮組織、血液、脾臟和肝臟中均呈上調(diào)表達(dá)。本研究也發(fā)現(xiàn),Nramp基因在凡納濱對(duì)蝦肌肉中呈上調(diào)表達(dá),可能是該基因參與了肌肉生長(zhǎng)發(fā)育的免疫反應(yīng),且對(duì)蝦類的生長(zhǎng)與蛋白合成及消化密切相關(guān)。除了參與經(jīng)典的肌肉發(fā)育信號(hào)通路基因(MyoG和Myf5)外,本研究還篩選出一些與蛻皮、肌肉生長(zhǎng)和肌肉收縮等相關(guān)的基因,說明這些基因?qū)∪獾纳L(zhǎng)發(fā)育及蛻皮也發(fā)揮著至關(guān)重要的作用。凡納濱對(duì)蝦的生長(zhǎng)發(fā)育是經(jīng)過多次蛻皮而實(shí)現(xiàn),蛻皮伴隨著舊表皮的脫落、新表皮的形成及肌肉的收縮舒張等生理過程(閆允君等,2020)。朱景花等(2014)研究發(fā)現(xiàn),CTSL基因SNP位點(diǎn)與凡納濱對(duì)蝦的生長(zhǎng)速度密切相關(guān)。此外,Trypsin基因在凡納濱對(duì)蝦肌肉生長(zhǎng)發(fā)育中顯著下調(diào)表達(dá),可能是由于蛻皮過程需通過影響胰蛋白酶活性變化來實(shí)現(xiàn)(JuanCarlos and JulioHumberto,2009),但具體作用機(jī)理還需進(jìn)一步探究。
4 結(jié)論
通過轉(zhuǎn)錄組測(cè)序分析從快速生長(zhǎng)群體和慢速生長(zhǎng)群體的凡納濱對(duì)蝦肌肉組織中篩選出1408個(gè)差異表達(dá)基因(661個(gè)為顯著上調(diào)表達(dá)基因,747個(gè)為顯著下調(diào)表達(dá)基因),主要富集在溶酶體、氨基糖和核苷酸糖新陳代謝及鞘脂類代謝等通路上,在對(duì)蝦肌肉生長(zhǎng)發(fā)育過程中發(fā)揮重要作用。
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(責(zé)任編輯 蘭宗寶)
楊春玲(1979-),副研究員,主要從事水產(chǎn)動(dòng)物分子遺傳育種研究工作。先后主持廣西重點(diǎn)研發(fā)計(jì)劃項(xiàng)目“基于基因芯片的南美白對(duì)蝦分子育種技術(shù)研究”及廣西直屬公益性科研院所基本科研業(yè)務(wù)費(fèi)專項(xiàng)2項(xiàng)、廣西水產(chǎn)遺傳育種與健康養(yǎng)殖重點(diǎn)實(shí)驗(yàn)室自主研發(fā)項(xiàng)目2項(xiàng);作為科研骨干參與完成國家級(jí)、省部級(jí)及地廳級(jí)科研項(xiàng)目20余項(xiàng);參與育成國審水產(chǎn)新品種1個(gè);參與制定國家農(nóng)業(yè)行業(yè)標(biāo)準(zhǔn)1項(xiàng)、廣西地方標(biāo)準(zhǔn)2項(xiàng);獲得廣西科技進(jìn)步二等獎(jiǎng)1項(xiàng);獲得授權(quán)發(fā)明專利4項(xiàng)、計(jì)算機(jī)軟件著作權(quán)10項(xiàng);參編出版專著5部;在《CryoLetters》《Fish and Shellfish Immunology》《BMC Genomics》《水生態(tài)學(xué)雜志》《南方農(nóng)業(yè)學(xué)報(bào)》《動(dòng)物醫(yī)學(xué)進(jìn)展》等學(xué)術(shù)期刊上發(fā)表科技論文20余篇。