Knowledge Resource Center for Ecological Environment in Arid Area
| 红砂叶片中基因表达及形态结构特征对干旱胁迫 | |
| 其他题名 | The responsive and adaptive mechanisms of gene expression and morphylogical characteristics in leaf |
| 刘美玲 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 李新荣 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 干旱是中国西北荒漠生态系统的主要特点之一，干旱对植物的生长、发育、繁殖及分布等产生重要的影响。红砂(Reaumuria soongorica (Maxim.) Pall)是广泛分布在我国温带荒漠草原生态系统中的优势种和主要建群种之一，对多种环境胁迫，尤其是干旱胁迫具有极强的耐受性。因此，研究红砂对干旱胁迫的响应及适应机理有着重要的科学意义。然而，由于基因组信息的缺失，目前对红砂的干旱适应机制仍缺乏系统深入的研究。本研究利用Illumina测序平台，采用De novo测序方法对不同胁迫处理的红砂叶片样本进行了转录组测序，获得了该植物大量的表达基因信息及分子标记；通过数字表达谱的方法分析红砂在转录水平上的基因表达变化对干旱的响应，探讨其适应干旱胁迫的分子机制；并对不同水分条件的自然生境中(小红山地区和长流水地区)的红砂叶片形态、表皮微形态及超微结构进行分析，揭示红砂适应干旱胁迫的叶片形态结构特征；从而从基因表达至形态结构不同水平，系统地探讨红砂对干旱胁迫的响应及适应机制。具体研究结果如下： (1) 转录组测序获得了66,117个unigenes，平均长度为722 bp，包含23,111个distinct clusters和43,006个distinct singletons。通过进行序列相似性比对，其中有38,762个(58.62%)基因在核苷酸或蛋白数据库中有同源性。基因的物种分布结果显示，红砂转录组序列与葡萄(Vitis vinifera)的相似性最高，为42.8%。在获得注释结果的unigene中，有29,460个基因注释到GO(Gene Ontology)数据库三大功能分类的55个分支中，其中9,833和171个unigenes分别注释到“响应刺激信号”与“抗氧化活性”功能分支。有21,202(32.06%)个unigenes被注释到128条KEGG代谢通路中，其中“代谢路径”(4,669 unigenes)，“次生代谢产物”(2,292 unigenes)和“植物激素信号转导”(988 unigenes)路径中注释到的基因数目最多。此外，鉴定得到大量的分子标记，包括7,711条简单重复序列(simple sequence repeats，SSRs)和216,851个单核苷酸多态性序列(single nucleotide polymorphisms，SNPs)。 (2) 对照材料与干旱胁迫下的基因表达谱分析显示，两个文库中分别得到212,338和211,052个标签，总共鉴定得到1,325个基因为差异表达基因(Differentially expressed genes, DEG)。红砂在干旱胁迫后，379个(28.6%)DEG表达量发生上调，946个(71.4%)DEG表达量显著下调。基因功能分析鉴定得到大量具有重要生物功能的差异表达基因，包括大量编码光合作用相关蛋白，调控蛋白，功能蛋白以及被其他胁迫因子所诱导的蛋白的基因。参与光合作用的相关蛋白(光系统I或II蛋白、叶绿素a/b结合蛋白、捕光蛋白及ATP合成酶等)发生显著下调，表明红砂的光合作用在干旱胁迫下发生明显抑制。调控蛋白(包括转录因子和蛋白激酶)表达量的改变可能参与到红砂将感知到的外界干旱胁迫信号转导至细胞内的信号转导过程。功能蛋白包括类黄酮生物合成蛋白、晚期胚胎富集蛋白、小热休克蛋白、水通道蛋白、脯氨酸转运子以及脂质转移蛋白在红砂响应干旱胁迫中发挥保护功能。 (3) 对不同土壤水分生境中(小红山和长流水地区)的红砂叶片形态结构特征分析显示：随着生境中土壤含水量的降低，红砂叶片厚度增大，叶面积及气孔开度减小，角质层增厚，从而降低植物蒸散过程中体内水分的散失。表皮细胞面积减小，表皮细胞密度增大，细胞壁增厚，增加了表皮细胞弹性，有助于降低干旱胁迫下植物失水造成的机械损伤。与此同时，栅栏组织增厚，且细胞排列更加致密，海绵组织的厚度减小，在一定程度上促进叶片的光合所用进行。因此，红砂叶片的形态结构特点使其对干旱具有极强的耐受性。 综上所述，在干旱胁迫下，红砂的光合作用受到明显的损伤，但同时在基因水平上通过有效地信号转导途径激活下游功能蛋白的表达，对其发挥保护作用；在叶片形态结构水平，通过降低蒸散过程中对水分的散失，增强表皮细胞弹性减轻失水造成的机械损伤，发达的栅栏组织提高叶片的光合效率；从而从基因表达到形态特征不同水平上，系统的响应干旱胁迫，适应干旱逆境。本研究揭示了荒漠植物红砂对干旱胁迫的响应及适应机制，为荒漠生态系统修复、固沙物种的选育提供了理论参考和数据支持。 |
| 英文摘要 | Drought is one important characteristic of desert ecosystem in northwest of China. It has great influence on growth, development, reproduction and distribution of plants. Reaumuria soongorica (Pall.) Maxim., a xerophytic semi-shrub, is a typical dominant and constructive species of desert or semi-desert ecosystems in northwestern China. It can survive in extreme environments, especially in water deficit. However, due to the lack of genomic information, systemic and thorough understanding of adaptive mechanisms to drought stress in R. soongorica is still limited. In this study, the stress-related transcriptome of R. soongorica was sequenced by De novo with Illumina platform, thus a number of gene sequences and molecular markers were gained. On the basis of an available transcriptome, the differentially expressed genes (DEGs) under control and drought stressed groups were investigated to explore the responsive mechanisms of gene expression to drought in R. soongorica. Furthermore, morphological and structural characteristics of leaf which selected from two habitats with different soil water content were analyzed to elucidate the adaptive mechanism of leaf characteristics. The aims of this study were expected to gain a further and systematic understanding of the responsive and adaptive mechanism to drought stress in R. soongorica, from gene to morphology. The main results are as follows: (1) De novo assembly produced 66,117 unigenes with an average length of 722 bp, including 23,111 distinct clusters and 43,006 distinct singletons. Based on sequence similarity with public databases, 38,762 (58.62%) genes had known homologs in nucleotides and protein databases. The species distribution of genes analysis showed that the transcriptome of R. soongorica was most homologous to Vitis vinifera (42.8%). Out of these annotated unigenes, 29,460 unigenes matched to 55 terms of gene ontology (GO) classification, including “response to stimulus” (9,833 unigenes) and “antioxidant activity” (171 unigenes) terms. Searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) showed that 21,202 (32.06%) unigenes were classified to 128 KEGG pathways, such as metabolism pathway (4,669 unigenes), biosynthesis of secondary metabolites (2,292 unigenes) and plant hormone signal transduction (988 unigenes). In addition, 7,711 simple sequence repeats (SSRs) and 216,851 single nucleotide polymorphisms (SNPs) were identified as potential molecular markers. (2) Digital gene expression analysis was performed using Illumina technique to investigate differentially expressed genes (DEGs) between control and PEG-treated samples of R. soongorica. A total of 212,338 and 211,052 distinct tags were detected in the control and PEG-treated libraries, respectively. A total of 1,325 genes were identified as DEGs, 379 (28.6%) of which were up-regulated and 946 (71.4%) were down-regulated in response to drought stress. Functional annotation analysis identified numerous drought-inducible genes with various functions in response to drought stress. Genes encoding proteins involved in photosynthesis were down-regulated, including photosystem I/II proteins, chorophyll a/b binding proteins, light-harvest comples and ATP synthase, which indicated impared photosynthesis under drought stress. A number of regulatory proteins, functional proteins, and proteins induced by other stress factors in R. soongorica were identified. Alteration in the regulatory proteins (transcription factors and protein kinase) may be involved in signal transduction. Functional proteins, including flavonoid biosynthetic proteins, late embryogenesis abundant (LEA) proteins, small heat shock proteins (sHSP), and aquaporin and proline transporter may play protective roles in response to drought stress. Flavonoids, LEA proteins and sHSP function as reactive oxygen species scavenger or molecular chaperone. Aquaporin and proline transporters regulate the distribution of water and proline throughout the whole plant. The tolerance ability of R. soongorica may be gained through effective signal transduction and enhanced protection of functional proteins to reestablish cellular homeostasis. DEGs obtained in this study may provide useful insights to help further understand the drought-tolerant mechanism of R. soongorica. (3) The morphological and structural characteristics of leaf from two habitats with different soil water content showed that: with the decreasing of soil water content, the thickness of leaf and cuticle increased, and the leaf area and stomata opening decreased. All those alternation were considered to be strategies to reduce water loss to a minimum in transpiration process. Increase of epidermal cell size, density and cell wall thickness could improve the plasticity of epidermal cells, consequently mitigate the mechanical damage in water loss process. Meanwhile, the thickness and density of palisade tissue increased, resulting in the improvement of photosynthesis rate. Under drought stress, photosynthesis was impared in R. soongorica. Meanwhile, the signal transduction pathway were trigged effectively to activated the functional proteins, playing protective role at molecular level; the characteristics of leaf epidermal morphology involved in reducing water loss in transpiration, mitigating mechanical damage caused by rapid water loss, and improvement of photosynthesis rate. This study helps to elucidate the responsive and adaptive mechanisms to drought stress in R. soongorica. This study revealed the responsive and adaptive mechanism of R. soongorica to drought stress, and provided theoretical reference for selection of sand-fixing plant in desert ecosystem restoration. |
| 中文关键词 | 红砂 ; 干旱 ; 转录组 ; 基因差异表达 ; 形态结构 |
| 英文关键词 | R. soongorica drought transcriptome differentially expressed genes morphology |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287515 |
| 推荐引用方式 GB/T 7714 | 刘美玲. 红砂叶片中基因表达及形态结构特征对干旱胁迫[D]. 中国科学院大学,2015. |
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