摘  要:COBRA家族是植物特有的基因家族，在调控细胞壁机械强度和根的定向生长中发挥重要作用。COBRA在水稻、拟南芥等物种中已有较多研究，但在玉米中的成员和功能还少有报道。本研究采用生物信息学方法鉴定出玉米中10个COBRA基因。系统发育分析表明，该家族蛋白可分为2个亚族，说明其序列和功能已经发生了分化；在系统发育树的末端鉴定出3对旁系同源基因，说明该家族在玉米中以物种特异的方式进行了扩张。基因复制分析表明，有1对基因起源于串联复制事件。基于芯片数据的表达分析表明，玉米COBRA的表达已经发生了分化，部分基因在成熟叶、果穗或发育中的种子等器官中表达，部分基因在根、茎和幼叶中表达。80008

毕业论文关键词：玉米，COBRA基因，系统发育分析，表达分析

Abstract: COBRA family is a plant specific gene family, whose members play important roles in regulation of cell wall mechanical strength and root orientational growth。 COBRAs have been widely studied in plant species such as rice and Arabidopsis。 However, their members and function in maize remain illusive。 In this study, we identified 10 COBRA genes from maize using bioinformatics approachs。 Phylogenetic analysis revealed that ZmCOBRA proteins were pided into two subfamilies, suggesting that pergence has occurred in this family。 Three pairs of paralogous genes were found at the terminal branches of the phylogenetic tree, indicating that this family has expanded in a species-specific manner。 Gene duplication analysis showed that one pair of ZmCOBRA genes was originated from tandem repeat event。 Gene expression analysis using microarry data demonstrated that the expression profiles of maize COBRA genes have perged; some of them were expressed in tissues and/or organs such as mature leaves, cobs or developing seeds, some of them were expressed in roots, culms and young leaves。 

Key words: maize, COBRA, phylogenetic analysis, expression analysis

目  录

1  引言 4 

2  材料与方法 4

2。1  序列检索和基因家族成员鉴定 4

2。2  染色体分布和基因复制分析 4

2。3  系统发育分析 5

2。4  基因表达分析 5

3  结果与分析 5

3。1  玉米中的COBRA基因 5

3。2  玉米COBRA基因家族的染色体分布 7

3。3  玉米COBRA家族的系统发育分析 7

3。4  玉米COBRA基因表达分析 8

讨论 10

参考文献 11

致谢 12

1  引言

细胞壁与植物的生长发育密切相关。它不仅为植物提供基本的机械支撑，而且为植物的细胞扩增提供足够的可塑性[1]。目前，植物细胞壁合成和扩张的机制还不明确。研究表明，拟南芥COBRA基因通过影响纤维素的含量和方向在壁细胞扩张的调控中发挥重要作用[2-3]。该基因编码一种GPI（glycosylphosphatidylinositol）锚定蛋白，具有氨基端分泌信号肽、亲水的中间部分、高度疏水的羧基末端、纤维素结合位点等结构[4]。COBRA突变导致细胞壁纤维素不能正确积累，最终引起根、茎细胞形态异常，纤维素含量下降，组织变脆[3、5]。