摘要
为探究猕猴桃雌雄异株变异为雌雄同株的分子机制,本研究对满天红猕猴桃雌雄同株变异株的雌花与雄花进行了转录组测序、生物信息学分析及qRT-PCR验证。转录组差异表达基因鉴定结果表明,雌花和雄花间共有337个差异表达基因,雄花中有241个基因表达量上调,有96个基因表达量下调。差异表达基因的GO与KEGG富集结果表明,与雌花相比,雄花中上调的基因主要参与氨基糖和核苷酸糖的代谢以及次生代谢物合成等路径;下调的基因则主要富集在次生代谢物合成、类胡萝卜素合成等途径。通过功能注释分析出30个潜在的性别相关调控基因,其中5个在次生代谢产物合成路径中表达。选取7个差异表达基因进行qRT-PCR验证,其在雌花、雄花中的表达水平与转录组数据一致。本研究结果为猕猴桃雌雄同株材料的创制提供了一定的理论依据。
猕猴桃(Actinidia)是一种营养价值极高的水果,含有多种对健康有益的成分,如维生素E、维生素C、维生素K以及纤维、钾和铁等,具有增强免疫系统、保护心脏健康等多方面的生理功
雌雄异株在有花植物中很少见(6%),但在作物中占比较高(20%),如椰枣(Phoenix dactylifera L.)、芦笋(Phoenix dactylifera L.)、柿子(Diospyros kaki Thunb.)等作
目前已报道了猕猴桃性别决定的重要区间和关键基因,然而关于猕猴桃雌雄花同株的分子机理研究较少。本研究分析自然变异的雌雄花同株的满天红猕猴桃转录组数据,探究不同性别花器官中基因表达差异,筛选与性别调控相关的候选基因,为培育猕猴桃雌雄异株的新种质提供科学依据。
在中国科学院武汉植物园种质资源圃中选取1株自然变异的雌雄花同株的满天红猕猴桃植株(

图1 满天红猕猴桃变异株雌花与雄花同株
Fig.1 Female and male flowers on the same plant of Mantianhong kiwifruit mutant
使用MaGen植物总 RNA 小提试剂盒(R4151-02),雌花与雄花各10朵为一个重复,分别提取满天红雌雄花3个重复的总RNA,使用Nanodrop分光光度计评估RNA纯度,并用Qubit测量RNA浓度及Agilent 2100分析RNA的完整性。将质量检测合格的总RNA送于北京诺禾致源生物信息科技有限公司进行cDNA文库构建及转录组测序。
将测序得到的原始序列进行过滤,去除含有接头的、不明碱基含量超过10%以及低质量的读段,得到clean data。将得到的clean data使用TopHat2软件比对到“Hongyang”猕猴桃参考基因组序列上(https://www.ncbi.nlm.nih.gov,登录号为PRJNA54 9770)。
利用HTSeq软件计算每个样本中所有基因的表达量,使用FPKM(Fragments Per Kilobase of exon model per Million mapped fragments)对每个基因的表达量进行量
通过对基因功能注释分析,选取7个与满天红变异株性别转换相关的差异表达基因,用 Oligo 7 软件设计特异引物(
基因编号 Gene ID | 注释 Annotated | 引物序列(5′-3′) Primer sequence (5′-3′) |
---|---|---|
Ac06484 | 天冬氨酸蛋白酶(PCS1) |
F:TCATATTGCACCCCACTTCG R:GAGCCGTAGTCCAACCATCG |
Ac07664 | 枯草杆菌蛋白酶样 |
F:AAGAACAGCATCAATGGCTTCG R:GCCACACACCATTGTCCAAG |
Ac35241 | 乙烯响应元件结合因子4 (ERF4) |
F:GCCTATTACCGCCGTTTCCC R:AGGTCGTAAATCGGCTACCTT |
Ac11873 | 乙烯合成(ACO4) |
F:ATCCGAACAAGATCATAGGAAG R:CTCGGAGACCCTTGATCAGC |
Ac09980 | NAC转录因子(RD26) |
F:GCACGTCAGCAATCACAACA R:TACCGAATACTGAACGGGTCT |
Ac19467 | MADS-box (AG) |
F:CATTAGCAGGATCCGCTCCA R:AGGCTGCATCAACTCATACTCA |
Ac14904 | 转录因子(CES) |
F:GGCCAAGCTACTGATAGTCAC R:TAGAACAAACTTGCTGCCGAA |
AcActin |
F:TGAGAGATTCCGTTGCCCAGAAGT R: TTCCTTACTCATGCGGTCTGCGAT |
对猕猴桃雌花与雄花样品进行转录组测序,分别获得58008756条和62485268条原始序列数,去除杂质、低质量读数和模糊读数后各得到55823704条和59684578条净序列数,雌花、雄花序列的Q20 > 94.5%,Q30 > 90%,GC含量均高于46%,与参考基因组比对率超过74%,其中平均大约72.39%比对到基因组的唯一序列(
样本 Sample | 原始序列数 Raw reads | 净序列数 Clean reads | GC 含量(%) GC content | 对比参考基因组序列 Mapped reads | 比对到唯一序列占比(%) Unique mapped reads | 比对到多个序列占比(%) Multi mapped reads | Q20 (%) | Q30 (%) |
---|---|---|---|---|---|---|---|---|
满天红雌花 MTH-FF | 58008756 | 55823704 | 46.09 | 41799841 (74.88%) | 72.36 | 2.52 | 95.10 | 90.49 |
满天红雄花 MTH-MF | 62485268 | 59684578 | 46.01 | 44711812 (74.91%) | 72.41 | 2.50 | 94.97 | 90.25 |
括号内数据:对比参考基因组序列/净序列数×100%
MTH-FF:Mantianhong female flower;MTH-MF:Mantianhong male flower;Bracketed data:Mappe reads/Clean reads×100%

图2 满天红猕猴桃变异株雌花与雄花整体差异基因聚类图(A)和差异基因表达情况(B)
Fig. 2 Differential gene class diagram (A) and differential gene expression (B) of female flowers and male flowers of Mantianhong kiwifruit mutant
灰色圆点表示表达量无显著差异的基因
Grey dots represent genes with no significant difference in expression levels
对满天红变异株的雄花与雌花的差异基因进行GO富集分析(

图3 满天红猕猴桃变异株雌花与雄花的差异表达基因的 GO 富集
Fig. 3 GO enrichment of differentially expressed genes in female and male flowers of Mantianhong kiwifruit mutant
A为上调基因的 GO 富集;B为下调基因的 GO 富集
A is the GO enrichment of up-regulated genes ; B is GO enrichment of down-regulated genes
差异表达基因的KEGG富集分析能够揭示相关代谢途径的变化。与雌花相比,雄花中上调的基因主要参与氨基糖和核苷酸的代谢过程(Amino sugar and nucleotide sugar metabolism)、次级代谢产物的生物合成(Biosynthesis of secondary metabolites)、苯丙烷类化合物的生物合成途径(Phenylpropanoid biosynthesis)、二萜类化合物的合成(Diterpenoid biosynthesis)、类黄酮生物合成(Flavonoid biosynthesis)以及半乳糖的代谢(Galactose metabolism)等生物学过程(

图4 满天红猕猴桃变异株雌花与雄花差异表达基因的KEGG富集
Fig 4 KEGG enrichment of differentially expressed genes in female and male flowers of Mantianhong kiwifruit mutant
A为上调基因的 KEGG 富集;B为下调基因的 KEGG 富集
A is the KEGG enrichment of up-regulated genes ; B is KEGG enrichment of down-regulated genes
为了筛选猕猴桃雌雄同株性别调控的候选基因,通过差异表达基因的功能注释,发现30个可能与性别调控相关的差异表达基因(
分类 Classification | 基因名称 Gene name | 表达水平 Expression level | q值 q-value | 基因功能 Gene function | ||
---|---|---|---|---|---|---|
雌花 FF | 雄花 MF | 差异倍数的对数 Log2 (Fold change) | ||||
花发育相关类 Flower development related class | Ac07664 | 11.70 | 0 | 5.69 | 6.41E-06 | 枯草杆菌蛋白酶样 |
Ac13530 | 5.96 | 0.22 | 4.59 | 6.54E-04 | 枯草杆菌蛋白酶样 | |
Ac06826 | 29.08 | 1.35 | 4.26 | 1.28E-06 | GDSL脂酶 | |
Ac03740 | 35.26 | 2.84 | 3.46 | 3.67E-04 | FLA蛋白 | |
Ac40034 | 43.06 | 6.13 | 2.64 | 1.82E-04 | FLA蛋白 | |
Ac06484 | 37.98 | 81.05 | -1.26 | 3.61E-04 | 天冬氨酸蛋白酶 | |
Ac14888 | 114.88 | 242.52 | -1.25 | 2.37E-09 | kcs合酶 | |
Ac19151 | 35.26 | 65.61 | -1.06 | 3.35E-03 | BEL1样蛋白 | |
Ac21949 | 3529.18 | 6366.28 | -1.02 | 1.18E-124 | 富含脯氨酸蛋白 | |
Ac14628 | 90.23 | 161.01 | -1.00 | 3.87E-09 | kcs合酶 | |
激素相关类 Hormone-related class | Ac35241 | 26.62 | 77.89 | -1.72 | 2.53E-03 | ERF |
Ac11873 | 430.43 | 15.41 | 4.64 | 1.93E-90 | 乙烯合成 | |
Ac14075 | 113.45 | 239.44 | -1.25 | 9.37E-18 | DXP酶 | |
Ac14734 | 1523.86 | 2871.69 | -1.08 | 1.52E-163 | NCED酶 | |
Ac09777 | 22.95 | 2.21 | 3.21 | 6.94E-06 | SCR转录因子 | |
Ac21198 | 24.54 | 4.44 | 2.30 | 1.54E-03 | 赤霉素合成 | |
Ac00695 | 50.29 | 9.72 | 2.20 | 1.40E-03 | TIR1 | |
Ac39840 | 25.13 | 6.92 | 1.69 | 2.41E-03 | PIN1C | |
Ac20399 | 96.02 | 30.66 | 1.48 | 9.77E-07 | IAA蛋白 | |
Ac10261 | 508.13 | 189.53 | 1.25 | 8.05E-39 | IAA蛋白 | |
转录因子类 Transcription factors | Ac09980 | 100.45 | 182.08 | -1.03 | 1.02E-04 | NAC转录因子 |
Ac19467 | 76.37 | 18.03 | 1.91 | 1.75E-04 | MADS-box | |
Ac14904 | 63.02 | 4.54 | 3.63 | 1.86E-09 | 转录因子 | |
Ac25144 | 75.36 | 8.10 | 3.05 | 2.07E-10 | MYB转录因子 | |
Ac05315 | 75.52 | 10.54 | 2.67 | 3.83E-12 | MYB转录因子 | |
Ac15025 | 30.48 | 4.37 | 2.64 | 7.18E-04 | 转录因子 | |
Ac38831 | 224.10 | 37.11 | 2.43 | 7.14E-26 | MYB转录因子 | |
Ac23565 | 53.10 | 9.44 | 2.32 | 6.47E-05 | 同源盒-亮氨酸拉链蛋白样 | |
Ac05314 | 63.27 | 12.28 | 2.20 | 5.85E-05 | R3-MYB转录因子 | |
Ac13145 | 60.03 | 12.14 | 2.14 | 1.73E-07 | MYB转录因子 |
为验证猕猴桃雌花与雄花转录组测序数据的准确性和有效性,选取上调与下调差异表达最明显的基因,包括2个花发育相关的蛋白基因(Ac06484和Ac07664)、2个植物激素相关的基因(Ac35241和Ac11873)和3个转录因子基因(Ac09980、Ac14904和Ac19467)进行qRT-PCR分析验证(

图5 满天红猕猴桃雄花和雌花中差异表达基因的 qRT-PCR 分析
Fig. 5 qRT-PCR analysis of differentially expressed genes in male and female flowers of Mantianhong
植物性别决定是植物研究的热点问题。目前已经在野生葡
植物性别相关的遗传因素主要分为两类:性别决定基因和性别分化基因。性别决定基因位于性染色体上,并在雌性和雄性个体或其性器官的发展中扮演着决定性角色。而性别分化基因则表现出在不同组织、器官和个体间的表达差异,并且在雌雄同株植物的花序分生组织中通过选择性的表达模式来决定不同性别花的形
植物激素在植物性别分化中发挥重要的调控作用。Sun
本研究中雌株满天红出现变异开出雌雄两种花,通过比较分析同株植物中雌花与雄花的转录组,结合差异表达基因的筛选与鉴定,以及GO富集和KEGG富集分析,结果表明次级代谢的生物合成途径对雌雄花变异起着显著作用。同时,检测到2个花发育相关的蛋白基因、2个植物激素相关的基因和3个转录因子基因可能参与猕猴桃的性别分化。对这些关键基因和转录因子的功能进行深入研究,有助于进一步探究雌雄花变异的分子机制,为猕猴桃雌雄同株新种质的培育提供重要的理论依据。
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