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Construction of SSH Library with Different Stages of Seeds Development in Brassica napus L.

甘蓝型油菜种子不同发育时期SSH文库的构建


Mechanism of fatty acid metabolic is a significant research topic in rapeseed molecular breeding. There are six hundreds genes and ESTs associated with fatty acid metabolism, 14% of which are conformed to participate in acrylic-fatty acid metabolism, 86% of which are speculated on sequences similarity and conservative domain with other species. But compared to the situation in Arabidopsis thaliana, molecular regulation mechanism of fatty acid metabolism in rapeseed has been less reported. In harvested rapeseed seeds, there is difference in seed fatty acid components among different varieties or the same variety grown under different ecological conditions. To further explore the molecular mechanism of fatty acid metabolic regulation of Brassica napus L., we investigated the assimilation product transition during the seed development. The starch reached a peak content at 20 days after pollination (20DAP) and was used up quickly after 20DAP, immediately the fatty acids content rapidly increased from 30DAP to 35DAP. According to the results, 20DAP developing seeds and 35DAP developing seeds were chosen for suppression subtractive hybridization (SSH), which is an effective tool for picking out specific expression genes among different samples. Two libraries, 20DAP SSH library derived from 20DAP seed cDNA as tester and 35DAP seed cDNA as driver and 35DAP library from 20DAP seed cDNA as driver and 35DAP seed cDNA as tester were constructed. The two SSH libraries had a high quality with high suppression subtractive efficiency after tested by PCR and RT-PCR. A total of 489 clones were randomly selected from the two libraries for sequencing and 452 high quality sequences tags were obtained. Blast analysis and functional annotation showed that most of the genes in 20DAP SSH library were relative to carbohydrate metabolism, while those in 35DAP library relative to fatty acid metabolic regulation. Significantly, 5 function-unknown genes in 20DAP library and 7 in 35DAP library were found out. In summary, this work adds an extra layer of complexity to the regulation of starch-to-oil transition and at the same time the different genes, especially the function-unknown genes shed light on studies of molecular mechanism of fatty acid metabolic regulation in seeds of Brassica napus L.


全 文 :作物学报 ACTA AGRONOMICA SINICA 2009, 35(9): 1576−1583 http://www.chinacrops.org/zwxb/
ISSN 0496-3490; CODEN TSHPA9 E-mail: xbzw@chinajournal.net.cn

本研究由国家重点基础研究发展计划(973计划)项目(2006CB101603)资助。
*
通讯作者(Corresponding authors): 刘春林,E-mail: liucl100@126.com; 阮颖,E-mail: yingruan@hotmail.com, Tel: 0731-84635294
第一作者联系方式: E-mail: p3072001@yahoo.com.cn
Received(收稿日期): 2009-01-02; Accepted(接受日期): 2009-04-26.
DOI: 10.3724/SP.J.1006.2009.01576
甘蓝型油菜种子不同发育时期 SSH文库的构建
彭 琦 1 胡 燕 1 杜培粉 1,2 谢青轩 1,2 阮 颖 1,2,* 刘春林 1,*
1 作物种质创新和资源利用国家重点实验室培育基地; 2 湖南农业大学生命科学技术学院, 湖南长沙 410128
摘 要: 利用抑制差减杂交技术构建了 20 d和 35 d甘蓝型油菜湘油 15发育种子特异表达基因的 SSH文库。随机挑
取单菌落进行 PCR表明, 文库质量较好。在 20 d 和 35 d SSH文库中随机挑选 489个阳性克隆进行测序, 获得 452
条高质量的表达序列标签(EST)。对序列进行 Blast比对及功能注释, 比较 20 d和 35 d SSH文库的基因表达谱, 发现
在 20 d SSH库中参与糖代谢的基因出现频率较高, 而在 35 d SSH库中与脂肪酸储存有关的油体蛋白家族、与脂肪酸
转运有关的柠檬酸合酶、与脂肪酸合成有关的酰基载体蛋白去饱和酶等, 参与油脂代谢相关基因出现频率较高。该
结果对进一步研究油菜脂肪酸代谢调控的分子机制打下了基础。
关键词: 甘蓝型油菜; 种子发育; 脂肪酸; 抑制差减杂交; cDNA文库
Construction of SSH Library with Different Stages of Seeds Development in
Brassica napus L.
PENG Qi1, HU Yan1, DU Pei-Fen1,2, XIE Qing-Xuan1,2, RUAN Ying1,2,*, and LIU Chun-Lin1,*
1 Pre-State Key Laboratory for Germplasm Innovation and Resource Utilization of Crops; 2 College of Bio-Science and Technology, Hunan
Agricultural University, Changsha 410128, China
Abstract: Mechanism of fatty acid metabolic is a significant research topic in rapeseed molecular breeding. There are six hun-
dreds genes and ESTs associated with fatty acid metabolism, 14% of which are conformed to participate in acrylic-fatty acid me-
tabolism, 86% of which are speculated on sequences similarity and conservative domain with other species. But compared to the
situation in Arabidopsis thaliana, molecular regulation mechanism of fatty acid metabolism in rapeseed has been less reported. In
harvested rapeseed seeds, there is difference in seed fatty acid components among different varieties or the same variety grown
under different ecological conditions. To further explore the molecular mechanism of fatty acid metabolic regulation of Brassica
napus L., we investigated the assimilation product transition during the seed development. The starch reached a peak content at 20
days after pollination (20DAP) and was used up quickly after 20DAP, immediately the fatty acids content rapidly increased from
30DAP to 35DAP. According to the results, 20DAP developing seeds and 35DAP developing seeds were chosen for suppression
subtractive hybridization (SSH), which is an effective tool for picking out specific expression genes among different samples.
Two libraries, 20DAP SSH library derived from 20DAP seed cDNA as tester and 35DAP seed cDNA as driver and 35DAP li-
brary from 20DAP seed cDNA as driver and 35DAP seed cDNA as tester were constructed. The two SSH libraries had a high
quality with high suppression subtractive efficiency after tested by PCR and RT-PCR. A total of 489 clones were randomly se-
lected from the two libraries for sequencing and 452 high quality sequences tags were obtained. Blast analysis and functional an-
notation showed that the most of genes in 20DAP SSH library were relative to carbohydrate metabolism, while those in 35DAP
library relative to fatty acid metabolic regulation. Significantly, 5 function-unknown genes in 20DAP library and 7 in 35DAP
library were found out. In summary, this work adds an extra layer of complexity to the regulation of starch-to-oil transition and at
the same time the different genes, especially the function-unknown genes shed light on studies of molecular mechanism of fatty
acid metabolic regulation in seeds of Brassica napus L.
Keywords: Brassica napus L.; Seeds development; Fatty acid; Suppression subtractive hybridization (SSH); cDNA library
抑制性消减杂交 (suppression subtractive hy-
bridization, SSH)技术是一种分离差异表达基因的有
效方法[1-2]。它主要利用了 cDNA链内退火优于链间
退火的动力学特性[3-4], 使非目的序列片段两端反向
重复序列在退火时产生类似“锅柄”的结构, 无法与
引物配对, 从而选择性地抑制了非目的基因序列片
第 9期 彭 琦等: 甘蓝型油菜种子不同发育时期 SSH文库的构建 1577


段的扩增。同时, 该方法还运用了杂交二级动力学
原理, 即丰度高的单链 cDNA 在退火时产生同源杂
交的速度要快于丰度低的单链 cDNA, 从而在杂交
完毕时原来在丰度上有差别的单链 cDNA 达到均一
化的目的。利用该技术已经从动植物的不同组织、
器官以及不同的发育时期成功地分离出了众多的差
异表达基因[5-9]。
脂肪酸代谢调控机理是油菜分子育种研究的一项
重要内容。纵观近几年的文献资料, 其中更多的只是
了解植物脂肪酸合成的部位与主要的生化过程[10-12]。
在拟南芥全基因组测序完成后, Beisson等[13]在基因
水平上对拟南芥种子脂肪酸合成代谢中涉及的相关
基因种类进行分析发现 , 与脂肪酸代谢相关的约
600 个基因和 EST 数据中, 只有 87 个(14%)是经过
实验确认参与酰脂代谢, 而其他 557个(86%)蛋白功
能仅仅是根据与其他物种进行序列相似性比较或保
守结构域推测而来。相对来说, 对油菜脂肪酸合成
代谢分子调控机理的了解更少。为了更好地利用油
菜这一重要的生物资源, 目前德国与加拿大等国在
借鉴现有拟南芥研究成果的基础上, 已经着手启动
油菜籽中脂肪酸合成的分子生物学机理研究。我国
是油菜生产大国, 必须加强这方面的研究。
本研究基于前期对甘蓝型油菜湘油 15 在不同
发育时期的种子胚进行的染色观察, 认为花后 20 d
种子中主要以淀粉积累为主; 花后 25 d种子中淀粉
颗粒有减少的趋势, 而且利用苏丹 III染色后部分区
域呈现橘色, 可以断定这即是淀粉积累到油脂合成
转换的关键时期; 花后 35 d种子中已经观察不到淀
粉颗粒的存在, 说明这个时期是油脂的直接合成阶
段(待发表)。然后, 我们利用气相色谱对不同时期种
子中各脂肪酸组分含量进行分析, 发现从花后 20 d
到 35 d是油酸的快速增长阶段。因此, 笔者选择开
花后 20 d和 35 d的油菜种子作为抑制性消减的材料
构建文库, 以期获得与油脂合成有关的重要功能基
因信息, 分析油酸高低含量变化的分子机制, 为后续
相关基因克隆和脂肪酸代谢调控机理研究奠定基础。
1 材料与方法
1.1 材料和试剂
甘蓝型油菜湘油 15 由湖南农业大学植物代谢调
控研究室提供, 于 2007年 9月中下旬种植于湖南农
业大学油菜基地, 翌年 4月分别采花后 20 d和 35 d
油菜的果荚 , 取种子以液氮速冻后于–80℃超低温
冰箱保存备用。
大肠杆菌 DH5α感受态细胞和 Trigol RNA提取
试剂盒均购自鼎国生物公司。Super SMARTTM PCR
cDNA Synthesis Kit, PCR-Select cDNA Subtraction
Kit, Advantage 2 PCR Kit 和克隆载体 pMD18-T
vector 均购自宝生物工程有限公司。其余试剂均为
国产分析纯。
1.2 种子总 RNA的分离与纯化
分别取湘油 15开花后 20 d和 35 d的种子, 加
入液氮充分研磨, 参照 Trigol 试剂盒操作说明提取
RNA。按 promega公司 DNaseI方法进行 DNA消化。
用 1.5%的琼脂糖凝胶电泳检测总 RNA 质量。最后
得到的总 RNA于–80℃保存备用。
1.3 SSH与 SSH cDNA文库的构建
依照 Super SMARTTM PCR cDNA Synthesis Kit
的说明进行 cDNA的合成与 Rsa I酶的消化。然后按
照 PCR-Select cDNA Subtraction Kit说明进行 SSH
操作。以花后 35 d的种子为检测子(tester)、花后 20
d 的种子为驱动子(driver), 构建油脂合成条件下特
异表达基因的 cDNA文库; 以花后 20 d的种子为检
测子(tester)、花后 35 d的种子为驱动子(driver)构建
淀粉积累条件下特异表达基因的 cDNA 文库。SSH
产物与 pMD18-T载体连接, 然后转化大肠杆菌感受
态细胞 DH5α, 涂于含有 Amp/X-gal/IPTG 的 LB 培
养基上 37℃过夜培养 , 随机挑取白色克隆 , 利用
M13 引物检测目的片段的插入情况 , 构成相应的
SSH菌落文库。
1.4 序列测定和 Blast分析
挑选阳性克隆进行测序后。对所获序列利用
DNAstar 软件进行剪切与拼接而得到不含载体序列
的 EST。采用 NCBI (http://blast.ncbi.nlm.nih.gov/ Blast.
cgi)的 nucleotide blast 在线序列比对工具, 对所有
EST 序列进行同源性检索分析。由上海华大基因公
司完成测序。
2 结果与分析
2.1 甘蓝型油菜种子总 RNA质量检测
琼脂糖凝胶电泳显示, 种子总 RNA 中的 28S
rRNA与 18S rRNA的亮度比例约为 2∶1, 经紫外分
光光度仪检测, A260/A280值在 1.8~2.0之间。表明所制
备的总 RNA质量较好, 达到了建库要求(图 1)。
2.2 第 1链合成和 LD-PCR扩增
根据上述测定结果 , 取适量种子总 RNA (2~
1000 ng)为模板, 进行第一链合成及其 LD-PCR。如
图 2和图 3分别是花后 20 d和 35 d种子的 LD-PCR
1578 作 物 学 报 第 35卷

结果。泳道 1~6分别表示不同循环数时的 PCR产物
电泳结果。
由图可知, 花后 20 d种子 LD-PCR产物电泳条
带主要集中在 500~4 500 bp 之间, 呈弥散分布, 其



图 1 油菜种子 RNA的电泳检测
Fig. 1 Detection of total RNA from rapeseed
20 d: 20DAP; 35 d: 35DAP.



图 2 花后 20 d种子第一链 cDNA的 LD-PCR
Fig. 2 LD-PCR of the first-strand cDNA for seeds at
20 d after anthesis
M: DNA marker3; 15~30: 不同循环数 PCR产物。
M: DNA marker3; 15–30: PCR product of different circles.



图 3 花后 35 d种子第一链 cDNA的 LD-PCR
Fig. 3 LD-PCR of the first-strand cDNA for seeds at
35 d after anthesis
M: DNA 100 bp ladder; 15~30: 不同循环数 PCR产物。
M: DNA 100 bp ladder; 15–30: PCR product of different circles.
中在 800 bp附近有非常明显的条带, 暗示种子在淀
粉积累过程中这个大小的基因表达丰度最高。花后
35 d 种子 LD-PCR 产物电泳条带主要集中在 300~
2 000 bp之间, 呈弥散分布, 其中在 700、900和 1 200
bp 等 3 处条带相对明显, 暗示油脂合成时期这几种
大小的基因表达丰度高。由于 LD-PCR 应选择在到
达反应平台期之前一个循环数时为最佳。根据这一
原则, 最后确定花后 20 d的最适循环数是 20个, 花
后 35 d的最适循环数是 17个。
2.3 抑制消减杂交
以 Primer-1 为引物进行第 1 次 PCR(图 4)。以
Nest PCR Primer-1和 Nest PCR Primer-2R为引物进
行第 2 次 PCR(图 5)。前者消减样无扩增产物(泳道
2), 或者电泳带很弱(泳道 4)。未消减样(泳道 1和 3)
有明显的扩增产物, 且呈弥散状。后者未消减样(泳
道 1和 3)产物条带变亮, 弥散分布于 300~2 000 bp;
消减样(泳道 2和 4)条带更加集中, 主要分布在 300~
1 500 bp。说明通过两次消减杂交达到了富集差异表
达基因片段并扣除非特异表达基因片段的目标。
2.4 差异表达 cDNA文库的 PCR产物检测
对随机挑取的克隆进行 PCR 检测, 除了有多条
扩增带的克隆和扩增带小于 200 bp 的克隆以外 ,
90%以上的克隆皆能扩增出有效产物。图 6 为 35 d
文库随机 PCR电泳图, 其扩增片段为 200~1 000 bp,
且多数在 800 bp 左右; 图 7 为 20 d 文库随机 PCR



图 4 第 1次 select-PCR产物
Fig. 4 Products of the first select-PCR
M: DNA 100 bp ladder; 1: 20 d 未消减样的扩增产物; 2: 20 d 消
减样的扩增产物; 3: 35 d 未消减样的扩增产物; 4: 35 d 消减样
的扩增产物。
M: DNA 100 bp ladder; 1: PCR products of 20 d unsubtracted tester
cDNA; 2: PCR products of 20 d subtracted tester cDNA; 3: PCR
products of 35 d unsubtracted tester cDNA; 4: PCR products of 35 d
subtracted tester cDNA.
第 9期 彭 琦等: 甘蓝型油菜种子不同发育时期 SSH文库的构建 1579




图 5 第 2次 select-PCR产物
Fig. 5 Products of the second select-PCR
M: DNA 100 bp ladder; 1: 20 d 未消减样的扩增产物; 2: 20 d 消
减样的扩增产物; 3: 35 d 未消减样的扩增产物; 4: 35 d 消减样
的扩增产物。
M: DNA 100 bp ladder; 1: PCR products of 20 d unsubtracted tester
cDNA; 2: PCR products of 20 d subtracted tester cDNA; 3: PCR
products of 35 d unsubtracted tester cDNA; 4: PCR products of 35 d
subtracted tester cDNA.

电泳图, 其扩增片段为 300~900 bp, 且多数在 500
bp左右。
2.5 EST测序分析
2.5.1 花后 35 d SSH 文库 ESTs 序列的功能分析
从 35 d文库中随机挑取 297个单克隆进行测序,
共获得 273个有效测序结果, 其中最短的 86 bp, 最
长的 838 bp。利用 NCBI数据库进行 Blastx比对, 去
除低质量序列及重复序列后, 共获得 70 条 EST 序
列。其中 60条功能已知, 占全部 EST的 85.7%; 在
Blastx 比对结果基础上 , 查阅相关资料并利用
AmiGO 对 60 条 EST 进行功能注释和聚类分析, 发
现其中 25%参与能量代谢, 20%参与植物防御, 其余
的涉及蛋白修饰、信号转导、转录调控因子、光合
作用、植物抗逆及衰老等多个方面。部分同源比较
结果见表 1。在已知功能的 EST 序列中得到可能与
油菜脂肪酸代谢密切相关的基因, 如与脂肪酸储存
有关的油体蛋白家族 (oleosin-T350004, T350033,
T350109, T350165)、与脂肪酸转运有关的柠檬酸盐
合酶 (citrate synthase-T350154)和苹果酸酯脱氢酶
(malate dehydrogenase-T350095)、与脂肪酸合成有关
的酰基载体蛋白去饱和酶(acyl-[acyl-carrier protein]
desaturase-T350038)以及酰基辅酶 A 氧化酶(acyl-CoA
oxidase-T350259)等。大部分 EST同源于芸薹属、拟
南芥等。



图 6 35 d消减文库部分克隆的 PCR检测
Fig. 6 PCR identification of inserted fragments in 35 days SSH-cDNA library
M: DNA marker3; 1~23: 单克隆菌落 PCR产物。
M: DNA marker3; 1–23: PCR product of single clone.



图 7 20 d消减文库部分克隆的 PCR检测
Fig. 7 PCR identification of inserted fragments in 20 days SSH-cDNA library
M: DNA marker3; 1~24: 单克隆菌落 PCR产物。
M: DNA marker3; 1–24: PCR product of single clone.
1580 作 物 学 报 第 35卷

表 1 35 d种子发育文库中的 EST与 GenBank功能已知基因相似性比较
Table 1 Similarity analysis of 35-days seed library EST with the function identified genes in GenBank
克隆编号
Sample code
长度
Length (bp)
可能基因
Putative identification
种属
Organism
一致性
Identity (%)
E值
E-value
T350001 449 glyceraldehyde-3-phosphate dehydrogenase Brassica napus 95 1.00E–68
T350002 389 60S ribosomal protein L39 Arabidopsis thaliana 86 2.00E–-80
T350004 356 oleosin BN-III Brassica napus 93 5.00E–41
T350005 504 gibberellin-regulated family protein Arabidopsis thaliana 65 2.60E–16
T350026 623 60S ribosomal protein L18A Arabidopsis thaliana 89 2.00E–172
T350033 589 oleosin 4 Arabidopsis thaliana 84 1.00E–143
T350038 339 acyl-[acyl-carrier protein] desaturase Brassica napus 97 5.00E–165
T350051 86 glycine-rich protein / oleosin Arabidopsis thaliana 84 3.00E–17
T350054 471 BnD12 Brassica napus 82 2.00E–60
T350056 838 PSI type III chlorophyll a/b-binding protein Arabidopsis thaliana 89 0
T350066 725 SOD 8A superoxide dismutase Brassica juncea 92 0
T350068 631 trypsin inhibitor 3 Brassica napus 98 0
T350072 145 ATP binding Arabidopsis thaliana 93 3.00E–54
T350074 758 heme oxygenase 1, HY1 Arabidopsis thaliana 82 6.00E–168
T350076 399 glutathione transferase Arabidopsis thaliana 87 3.00E–135
T350077 270 putative ribosomal protein L19 Arabidopsis thaliana 100 6.00E–32
T350078 219 low-molecular-weight cysteine-rich 23 Arabidopsis thaliana 78 1.00E–29
T350079 746 alpha - tonoplast intrinsic protein Arabidopsis thaliana 87 0
T350080 240 myrosinase Brassica napus 95 7.00E–103
T350092 333 transcription factor LIM Brassica rapa 96 4.00E–156
T350095 727 malate dehydrogenase Arabidopsis thaliana 88 0
T350101 239 histidine kinase Arabidopsis thaliana 75 5.00E–4
T350104 207 mitochondrial DNA Brassica napus 99 2.00E–88
T350106 803 60S ribosomal protein L5 Arabidopsis thaliana 89 0
T350107 584 ATHVA22B Arabidopsis thaliana 82 3.00E–120
T350109 771 OLEO2 Arabidopsis thaliana 78 4.00E–150
T350113 274 senescence-specific cysteine protease Brassica napus 99 7.00E–123
T350120 712 recombinant Ib pronapin precursor Brassica napus 97 9.00E–156
T350122 452 short-chain dehydrogenase/reductase (SDR) family protein Arabidopsis thaliana 84 9.00E–136
T350136 509 transaldolase Arabidopsis thaliana 91 8.00E–150
T350147 189 translationally controlled tumor protein (TCTP) Brassica oleracea 96 5.00E–83
T350152 682 tubulin alpha-2/alpha-4 chain (TUA2) Arabidopsis thaliana 59 4.10E–18
T350154 561 CSY2 (citrate synthase 2) Arabidopsis thaliana 85 0
T350156 341 trypsin inhibitor 2 Arabidopsis thaliana 74 5.00E–26
T350160 714 acyl-CoA oxidase 4 Arabidopsis thaliana 91 0
T350165 137 oleosin napII Brassica napus 90 2.00E–41
T350173 258 phytosulfokine 3 precursor Arabidopsis thaliana 83 2.00E–08
T350174 281 cruA gene for cruciferin Brassica napus 98 2.00E–138
T350175 311 Silique of strain col-0 Arabidopsis thaliana 84 1.00E–71
T350186 753 putative laccase Arabidopsis thaliana 86 0
T350187 71 napin (1.7S embryo-specific) storage protein gene Brassica napus 98 7.00E–27
T350190 251 cupin family protein Arabidopsis thaliana 89 5.00E–84
T350191 720 disease resistance response Arabidopsis thaliana 81 3.00E–121
T350197 736 ribulose 1,5-bisphosphate carboxylase Brassica napus 93 0
第 9期 彭 琦等: 甘蓝型油菜种子不同发育时期 SSH文库的构建 1581


(续表 1)
克隆编号
Sample code
长度
Length (bp)
可能基因
Putative identification
种属
Organism
一致性
Identity (%)
E值
E-value
T350209 195 protease inhibitor II Brassica rapa 94 1.00E–79
T350210 754 60S ribosomal protein L15 Arabidopsis thaliana 92 0
T350225 671 ribosomal protein L17 Arabidopsis thaliana 86 8.00E–171
T350230 735 pekinensis thionin Brassica rapa 71 5.00E–59
T350232 465 extensin proline-rich 1 Arabidopsis thaliana 81 3.00E–69
T350239 468 putative senescence-associated protein Arabidopsis thaliana 89 3.00E–163
T350246 322 acyldesaturase Brassica napus 95 3.00E–107
T350257 253 PSII-R protein Brassica campestris 99 1.00E–104
T350259 813 ACX4 Arabidopsis thaliana 91 0
T350260 334 nudix hydrolase homolog 3 Arabidopsis thaliana 90 2.00E–119
T350269 629 60S ribosomal protein L14 Arabidopsis thaliana 93 2.00E–162
T350270 712 Ib pronapin precursor Brassica napus 97 2.00E–152
T350277 308 MATH domain-containing protein Arabidopsis thaliana 72 5.00E–17
T350288 706 ubiquitin Arabidopsis thaliana 86 0
T35Blue 1 450 40S ribosomal protein S9 Arabidopsis thaliana 88 7.90E–75
T35Blue 3 266 protease inhibitor Arabidopsis thaliana 90 2.00E–88

2.5.2 花后 20 d SSH 文库 ESTs 序列的功能分析
从 20 d文库中随机挑取 192个单克隆进行测序,
共获得 179个有效测序结果, 其中最短的 118 bp, 最
长的 686 bp。利用 NCBI数据库进行 Blastx比对, 去
除低质量序列及重复序列后, 共获得 64 条 EST 序
列。其中已知功能的 34条占全部 EST的 53.1%; 在
Blastx 比对结果基础上 , 查阅相关资料并利用
AmiGO 对 34 条 EST 进行功能注释和聚类分析, 发
现与糖代谢有关的 EST 占 20.6%, 与植物抗病抗逆
有关的占 26.5%, 其他的涉及蛋白质代谢调控、种子
发育、转录因子等方面, 而几乎不含与油脂代谢有
关的基因。部分同源比较结果见表 2。
3 讨论
在本研究获得的 35 d EST库中, 发现了一些与
油脂合成有关的酶基因。如与脂肪酸储存有关的油
体蛋白家族(oleosin), 与脂肪酸转运有关的酰基载
体蛋白去饱和酶 (acyl-[acyl-carrier protein] desatu-
rase)等。前者是与油体特异性结合的一种碱性蛋白
质, 只存在于植物中 [14], 它对维持油体的稳定极为
重要。油体蛋白的积累晚于三酰甘油和酰基载体蛋
白去饱和酶的积累, 而酰基载体蛋白去饱和酶直接
参与脂肪酸的生物合成, 表明被磷脂单分子层包裹
的三酰甘油微油滴获得油体蛋白的包被是发生在油
体合成的后期[15]。
柠檬酸合酶(citrate synthase)在三羧酸循环过程
中催化草酰乙酸和乙酰辅酶 A 合成柠檬酸, 是 3 个
限速酶之一[16-17]。其活性变化直接导致细胞乙酰辅
酶 A池的变化, 而乙酰辅酶 A是脂肪酸合成的主要
原料来源, 乙酰辅酶 A 池的变化必将直接影响脂肪
酸的合成, 因此, 对这个酶的研究可以加深对糖代
谢和脂肪酸合成关系的了解 [18]。在拟南芥中发现 ,
溶酶体的柠檬酸合酶在种子萌发和脂肪酸动员中起
重要作用[19]。而且在含铝的土壤上, 拟南芥生长速
度和柠檬酸合酶的表达量呈正相关[20]。在油菜中, 该
酶是如何参与脂肪酸代谢调控的, 尚需进一步研究。
通过 20 d和 35 d EST库的比较发现, 20 d库中与糖
代谢有关的 EST 明显较多, 如 1-磷酸葡萄糖酰基转
移酶 (glucose-1-phosphate adenylyltransferase-
T200129), 糖苷水解酶(glycosyl hydrolase-T200106),
转氨酶(branched-chain amino acid transaminase-
T200107)等。而 35 d 库中又以脂肪酸代谢相关的
EST 为主。这恰好与不同时期种子内含物染色观察
的结果一致。这说明 35 d种子中特异表达的基因主
要参与了脂肪酸代谢的活动。除了直接参与脂肪酸
合成的酶, 还有一些具有特殊结构域的蛋白和转录
因子可能起着代谢调控这一类酶的作用, 或是间接
参与了脂肪酸代谢的过程。了解这些蛋白与转录因
子的功能对于我们阐明脂肪酸代谢调控的机制是很
有帮助的。研究中所获得的大部分 EST序列同源于
1582 作 物 学 报 第 35卷

表 2 20 d种子发育文库中的 EST与 GenBank功能已知基因相似性比较
Table 2 Similarity analysis of 20-days seed library EST with the function identified genes in GenBank
克隆编号
Sample
code
长度
Length
(bp)
可能基因
Putative identification
种属
Organism
一致性
Identity (%)
E值
E-value
T200001 557 gamma interferon responsive lysosomal thiol reductase Arabidopsis thaliana 85 1.00E–63
T200004 367 pectinesterase inhibitor Arabidopsis thaliana 82 8.00E–07
T200005 254 RNA polymerase alpha subunit Arabidopsis thaliana 100 3.00E–20
T200010 243 heavy-metal-associated domain-containing protein Arabidopsis thaliana 100 1.00E–15
T200011 304 clone O9 bet v I allergen family protein Brassica rapa 100 7.00E–32
T200013 624 myo-inositol 1-phosphate synthase Brassica napus 99 2.00E–60
T200022 605 senescence-specific cysteine protease Brassica napus 99 4.00E–113
T200027 338 pollen Ole e 1 allergen and extensin family protein Arabidopsis thaliana 93 3.00E–29
T200031 306 cystatin domain containing protein Brassica oleracea 80 3.00E–30
T200039 639 molybdenum cofactor sulfurase family protein Arabidopsis thaliana 92 5.00E–103
T200047 338 pollen Ole e 1 allergen and extensin family protein Arabidopsis thaliana 93 3.00E–29
T200058 265 nucleic acid binding / nucleotide binding Arabidopsis thaliana 70 1.00E–05
T200094 436 putative lipid transfer protein Arabidopsis thaliana 99 7.10E–90
T200096 197 glycerophosphoryl diester phosphodiesterase family protein Arabidopsis thaliana 80 5.00E–20
T200098 648 caffeoyl-CoA 3-O-methyltransferase, putative Arabidopsis thaliana 94 3.00E–74
T200103 636 MADS-box protein (AGL35) Arabidopsis thaliana 72 8.00E–50
T200106 629 glycosyl hydrolase family protein 17 Triticum aestivum 74 8.10E–30
T200107 657 branched-chain amino acid transaminase (bcat1 gene) Arabidopsis thaliana 96 2.00E–60
T200109 444 glycosyl hydrolase family 1 protein Arabidopsis thaliana 71 3.40E–26
T200121 584 subsp. pekinensis thionin Brassica rapa 94 1.00E–66
T200129 355 glucose-1-phosphate adenylyltransferase (ADG1) Arabidopsis thaliana 90 9.00E–84
T200131 655 calcium ion binding Arabidopsis thaliana 95 3.00E–60
T200133 660 putative 6-phosphogluconolactonase (6PGL) Brassica carinata 99 2.00E–68
T200139 666 MATH domain-containing protein Arabidopsis thaliana 93 3.00E–82
T200141 120 putative ROP family GTPase (ROP10) Brassica napus 95 1.00E–3
T200143 651 Dof-type zinc finger domain-containing protein Arabidopsis thaliana 62 9.00E–43
T200145 184 cysteine proteinase Arabidopsis thaliana 83 3.00E–22
T200147 417 polyadenylate-binding protein-related /PABP-related Arabidopsis thaliana 70 5.00E–25
T200153 606 pectinesterase family protein Arabidopsis thaliana 68 5.00E–58
T200158 653 beta-glucosidase, putative (BG1) Arabidopsis thaliana 88 1.30E–27
T200160 325 cysteine-type endopeptidase (DELTA-VPE) Arabidopsis thaliana 90 5.00E–20
T200168 281 putative auxin response factor 46 Arabidopsis thaliana 70 2.00E–15
T200173 639 2-oxoglutarate-dependent dioxygenase gene Brassica oleracea 97 8.00E–100
T2000B2 616 var. gemmifera LOX mRNA lipoxygenase 2 Brassica oleracea 98 4.00E–84

拟南芥中的一些功能蛋白, 而这些蛋白在油菜中的
功能研究还没有被报道过。
除了已知功能 EST, 本研究还获得了一些未知
功能 EST和推测蛋白。深入研究这一类序列的功能
可以为脂肪酸代谢相关新基因的开发提供新的资源
和基础。在后续研究中我们将着重对 35 d EST库中
的未知功能序列及部分调控蛋白的功能进行验证 ,
以阐明其作用机制。本研究的结果为继续开展油菜
脂肪酸代谢调控机理的研究缩小了范围并明确了方
向, 同时又为新基因的开发提供了新的资源。
4 结论
构建了甘蓝型油菜种子不同发育时期的 SSH文
库, 在 35 d发育文库中获得了一些可能与油脂形成
相关的特异表达基因及调控序列。其未知功能序列
也可能参与了脂肪酸代谢。
第 9期 彭 琦等: 甘蓝型油菜种子不同发育时期 SSH文库的构建 1583


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