Jagus Rosemary, Bachvaroff Tsvetan R, Joshi Bhavesh, Place Allen R
Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 E. Pratt Street, Baltimore, MD 21202, USA.
Comp Funct Genomics. 2012;2012:134839. doi: 10.1155/2012/134839. Epub 2012 Jun 20.
The greatest diversity of eukaryotic species is within the microbial eukaryotes, the protists, with plants and fungi/metazoa representing just two of the estimated seventy five lineages of eukaryotes. Protists are a diverse group characterized by unusual genome features and a wide range of genome sizes from 8.2 Mb in the apicomplexan parasite Babesia bovis to 112,000-220,050 Mb in the dinoflagellate Prorocentrum micans. Protists possess numerous cellular, molecular and biochemical traits not observed in "text-book" model organisms. These features challenge some of the concepts and assumptions about the regulation of gene expression in eukaryotes. Like multicellular eukaryotes, many protists encode multiple eIF4Es, but few functional studies have been undertaken except in parasitic species. An earlier phylogenetic analysis of protist eIF4Es indicated that they cannot be grouped within the three classes that describe eIF4E family members from multicellular organisms. Many more protist sequences are now available from which three clades can be recognized that are distinct from the plant/fungi/metazoan classes. Understanding of the protist eIF4Es will be facilitated as more sequences become available particularly for the under-represented opisthokonts and amoebozoa. Similarly, a better understanding of eIF4Es within each clade will develop as more functional studies of protist eIF4Es are completed.
真核生物物种的最大多样性存在于微生物真核生物（即原生生物）中，而植物和真菌/后生动物仅代表估计的75个真核生物谱系中的两个。原生生物是一个多样化的群体，其特点是具有不寻常的基因组特征和广泛的基因组大小，从顶复门寄生虫牛巴贝斯虫的8.2兆碱基对到米氏原甲藻的112,000 - 220,050兆碱基对。原生生物拥有许多在“教科书”模式生物中未观察到的细胞、分子和生化特征。这些特征对一些关于真核生物基因表达调控的概念和假设提出了挑战。与多细胞真核生物一样，许多原生生物编码多种真核起始因子4E（eIF4E），但除了寄生物种外，很少有功能研究。早期对原生生物eIF4E的系统发育分析表明，它们不能归类于描述多细胞生物eIF4E家族成员的三个类别中。现在有更多的原生生物序列可供使用，从中可以识别出三个与植物/真菌/后生动物类别不同的进化枝。随着更多序列的出现，特别是对于代表性不足的后鞭毛生物和变形虫，对原生生物eIF4E的理解将得到促进。同样，随着对原生生物eIF4E的更多功能研究的完成，对每个进化枝内的eIF4E也将有更好的理解。
