Dresselhaus T, Cordts S, Lörz H
Applied Plant Molecular Biology II, University of Hamburg, Germany.
Plant Mol Biol. 1999 Mar;39(5):1063-71. doi: 10.1023/a:1006176819213.
Differential screening of cDNA libraries of unfertilized egg cells and in vitro zygotes of maize resulted in the isolation of more than 50 different genes whose expression is up- or down-regulated after in vitro fertilization (IVF). Among these genes, we identified a cDNA encoding the eukaryotic translation initiation factor eIF-5A. This highly conserved factor is thought to be necessary for selective mRNA stabilization and translation. It is also the only known protein that contains the unusual amino acid hypusine which is required for biological activity. High transcript amounts are stored in the egg cell, which is, in terms of metabolism, relatively inactive. Upon fertilization transcript amounts decrease, in contrast to metabolically inactive embryos in which the transcript cannot be detected and transcript levels increase upon germination. The expression pattern during the first embryonic cell cycle is also different from that observed during the somatic cell cycle: egg cells in the G0 phase contain high transcript levels, while arrested suspension cells contain few transcripts. In the somatic cell cycle, eif-5A is strongly induced during the G1 phase and transcripts are continuously degraded during the S, G2 and M phases until new induction during the G1 phase of the next cycle. eif-5A, a member of a small gene family in maize, is expressed in most maize tissues investigated. Based on our results, we suggest that the unfertilized egg cell of maize, although relatively inactive regarding its metabolism, is prepared for selective mRNA translation that is quickly triggered after fertilization. We also suggest that the regulation of eif-5A in the first embryonic cell cycle is different from the somatic cell cycle.
对玉米未受精卵细胞和体外受精卵的cDNA文库进行差异筛选，分离出50多个不同的基因，其表达在体外受精（IVF）后上调或下调。在这些基因中，我们鉴定出一个编码真核翻译起始因子eIF-5A的cDNA。这个高度保守的因子被认为是选择性mRNA稳定和翻译所必需的。它也是唯一已知含有生物活性所需的不寻常氨基酸hypusine的蛋白质。卵细胞中储存着大量的转录本，就代谢而言，卵细胞相对不活跃。受精后，转录本数量减少，而代谢不活跃的胚胎中检测不到转录本，并且在萌发时转录本水平会增加。第一个胚胎细胞周期中的表达模式也与体细胞周期中观察到的不同：处于G0期的卵细胞含有高水平的转录本，而停滞的悬浮细胞含有少量转录本。在体细胞周期中，eif-5A在G1期被强烈诱导，转录本在S期、G2期和M期持续降解，直到下一个周期的G1期再次诱导。eif-5A是玉米中一个小基因家族的成员，在所研究的大多数玉米组织中都有表达。基于我们的结果，我们认为玉米未受精卵细胞尽管在代谢方面相对不活跃，但已为受精后迅速触发的选择性mRNA翻译做好了准备。我们还认为eif-5A在第一个胚胎细胞周期中的调控与体细胞周期不同。
