首页> 外文学位 >The evolution of the expansin gene superfamily in basal land plant lineages: Studies of expansins in Physcomitrella patens and Selaginella moellendorffii.
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The evolution of the expansin gene superfamily in basal land plant lineages: Studies of expansins in Physcomitrella patens and Selaginella moellendorffii.

机译:陆基植物谱系中expansin基因超家族的进化:帕氏假单胞菌和卷柏卷柏中expansins的研究。

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摘要

Expansins are an important superfamily of cell wall loosening proteins consisting of four families named EXPA, EXPB, EXLA, and EXLB. These proteins loosen the linkage between cellulose microfibrils in a non-enzymatic fashion, allowing these microfibrils to slide past one another. This loosening action has been implicated as being important in a wide variety of growth and developmental processes in plants. Because this protein superfamily appears to be critical for the proper growth and development of land plants, its origin and evolutionary history has become a question of great interest. Two recent papers from Sampedro et al. used gene colinearity data integrated with traditional phylogenetic analyses to define 17 orthologous groups of angiosperm expansins between Arabidopsis, Populus and rice. The work presented in this dissertation provides the first look at the makeup of the expansin superfamily in basal land plant lineages. The sequencing of the genomes of the bryophyte Physcomitrella patens and the lycophyte Selaginella moellendorffii by the Joint Genome Initiative of the Department of Energy allowed for the assembly of the expansin superfamily in these organisms. What is revealed are gene superfamilies containing EXPA and EXPB families but lacking EXLA or EXLB families. This indicates that the EXLA and EXLB families arose sometime after the divergence of the lycophytes, or that these divergent expansin families have been lost from early land plant lineages. The Physcomitrella EXPA sequences show a high degree of conservation at putatively critical amino acid residues, suggesting a conservation of biochemical function with angiosperm expansins. Phylogenetic analyses seem to indicate, however, that most of these genes are bryophyte-specific lineages paraphyletic to all angiosperm EXPA genes. The Physcomitrella EXPB genes appear to form a monophyletic group sister to all angiosperm EXPB genes, and they also show several changes at normally conserved amino acid residues. Both the EXPA and EXPB genes of Physcomitrella show a relatively variable intron pattern, but these patterns do not yet warrant a change to the ancestral expansin intron patterns hypothesized in the literature. Although Physcomitrella expansins appear to be evolving independently from their angiosperm counterparts, EXPA and EXPB gene families of similar sizes have evolved in parallel, indicating some critical importance of gene number for proper expansin function. In contrast to the apparently divergent history of the expansin superfamily in bryophytes, Selaginella possesses a superfamily, which, although still difficult to definitively relate to angiosperm clades, seems to be much more closely related to angiosperm expansins than to the Physcomitrella superfamily. It is even possible to firmly place two Selaginella EXPA genes as a sister group to an angiosperm clade. Preliminary expression pattern analysis of these two Selaginella EXPA genes indicates that they do not share the root-hair-specific expression pattern observed for the Arabidopsis members of this angiosperm EXPA clade. Selaginella EXPA and EXPB intron patterns are highly conserved and reflect the ancestral states proposed in earlier works. Preliminary expression pattern data for two Physcomitrella EXPA genes indicates that, like their angiosperm counterparts, bryophyte expansins are expressed in a tissue-specific manner consistent with a role in plant growth and development. This work also reveals that, like angiosperm expansins, certain Physcomitrella expansins seem to have their expression regulated by plant hormones. Although functionality studies (both in vivo and in vitro ) of Physcomitrella expansins presented here were not able to show a role for bryophyte expansins in cell growth or wall loosening, future work may well illuminate such a role using the lessons learned here as a starting point.
机译:扩展蛋白是细胞壁松弛蛋白的重要超家族,其由名为EXPA,EXPB,EXLA和EXLB的四个家族组成。这些蛋白质以一种非酶的方式使纤维素微纤维之间的连接松动,从而使这些微纤维彼此滑过。这种松弛作用被认为在植物的多种生长和发育过程中很重要。由于这种蛋白质超家族对于陆地植物的正常生长和发育至关重要,因此其起源和进化史已成为人们非常关注的问题。 Sampedro等人最近发表的两篇论文。利用基因共线性数据与传统的系统发育分析相结合,在拟南芥,胡杨和水稻之间定义了17个直系同源的被子植物扩展蛋白组。本文的工作为基础陆地植物谱系中的expandin超家族的组成提供了初步的认识。能源部的联合基因组计划对苔藓植物Physcomitrella patens和粘藻植物卷柏Selaginella moellendorffii的基因组进行测序,从而在这些生物体中组装了扩展蛋白超家族。揭示的是包含EXPA和EXPB家族但缺少EXLA或EXLB家族的基因超家族。这表明EXLA和EXLB家族是在苔藓植物分化后的某个时候出现的,或者这些分化的扩张蛋白家族已经从早期的陆地植物谱系中消失了。 Physcomitrella EXPA序列在假定的关键氨基酸残基上显示出高度的保守性,表明被子植物扩展蛋白具有生物化学功能的保守性。系统发育分析似乎表明,这些基因中的大多数是与所有被子植物EXPA基因有亲缘关系的苔藓植物特异性谱系。 Physcomitrella EXPB基因似乎形成了所有被子植物EXPB基因的单系群姐妹,并且它们在正常保守的氨基酸残基上也表现出一些变化。 Physcomitrella的EXPA和EXPB基因都显示出相对可变的内含子模式,但是这些模式尚不能保证文献中假设的祖先expansin内含子模式发生变化。尽管Physcomitrella expansins似乎独立于被子植物而进化,但相似大小的EXPA和EXPB基因家族已经并行进化,这表明基因数目对于适当的expansin功能至关重要。与苔藓植物中扩张蛋白超家族明显不同的历史相反,卷柏属拥有一个超家族,尽管仍然很难确定地与被子植物进化枝相关,但它似乎与被子植物扩张素的关系远比Physcomitrella超家族的密切。甚至有可能将两个卷柏EXPA基因作为姊妹组牢固地置于被子植物进化枝中。对这两个卷柏EXPA基因的初步表达模式分析表明,它们不具有被子植物EXPA进化支的拟南芥成员所观察到的根毛特异性表达模式。卷柏EXPA和EXPB内含子模式是高度保守的,反映了早期工作中提出的祖先状态。两个Physcomitrella EXPA基因的初步表达模式数据表明,与它们的被子植物对应物一样,苔藓植物扩展蛋白以与植物生长和发育中的作用一致的组织特异性方式表达。这项工作还表明,像被子植物的扩张素一样,某些小立碗藓扩张素的表达似乎也受到植物激素的调节。尽管此处介绍的Physcomitrella expansins的功能性研究(体内和体外)均无法显示苔藓植物expansins在细胞生长或壁松动中的作用,但今后的工作可能会以此处的经验为出发点很好地阐明这种作用。 。

著录项

  • 作者

    Carey, Robert Earl.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Biology Botany.Biology Evolution and Development.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 227 p.
  • 总页数 227
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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