Berg Michael, Rogers Rebecca, Muralla Rosanna, Meinke David
Department of Botany, Oklahoma State University, Stillwater, 74078, USA.
Plant J. 2005 Dec;44(5):866-78. doi: 10.1111/j.1365-313X.2005.02580.x.
Aminoacyl-tRNA synthetases (AARSs) are required for translation in three different compartments of the plant cell: chloroplasts, mitochondria and the cytosol. Elimination of this basal function should result in lethality early in development. Phenotypes of individual mutants may vary considerably, depending on patterns of gene expression, functional redundancy, allele strength and protein localization. We describe here a reverse genetic screen of 50 insertion mutants disrupted in 21 of the 45 predicted AARSs in Arabidopsis. Our initial goal was to find additional EMB genes with a loss-of-function phenotype in the seed. Several different classes of knockouts were discovered, with defects in both gametogenesis and seed development. Three major trends were observed. Disruption of translation in chloroplasts often results in seed abortion at the transition stage of embryogenesis with minimal effects on gametophytes. Disruption of translation in mitochondria often results in ovule abortion before and immediately after fertilization. This early phenotype was frequently missed in prior screens for embryo-defective mutants. Knockout alleles of non-redundant cytosolic AARSs were in general not identified, consistent with the absolute requirement of cytosolic translation for development of male and female gametophytes. These results provide a framework for evaluating redundant functions of AARSs in Arabidopsis, a valuable data set of phenotypes resulting from multiple disruptions of a single basal process, and insights into which genes are required for both gametogenesis and embryo development and might therefore escape detection in screens for embryo-defective mutants.
氨酰 - tRNA合成酶（AARSs）在植物细胞的三个不同区室（叶绿体、线粒体和细胞质）的翻译过程中是必需的。消除这种基本功能应该会在发育早期导致致死性。单个突变体的表型可能有很大差异，这取决于基因表达模式、功能冗余、等位基因强度和蛋白质定位。我们在此描述了对拟南芥中45个预测的AARSs中的21个被破坏的50个插入突变体进行的反向遗传筛选。我们最初的目标是找到在种子中具有功能丧失表型的其他EMB基因。发现了几类不同的敲除突变体，它们在配子发生和种子发育方面都存在缺陷。观察到三个主要趋势。叶绿体中的翻译中断通常会导致胚胎发育过渡阶段的种子败育，对配子体的影响最小。线粒体中的翻译中断通常会导致受精前和受精后立即出现胚珠败育。这种早期表型在先前对胚胎缺陷突变体的筛选中经常被遗漏。非冗余细胞质AARSs的敲除等位基因通常未被鉴定出来，这与雄性和雌性配子体发育对细胞质翻译的绝对需求一致。这些结果为评估拟南芥中AARSs的冗余功能提供了一个框架，是由单个基本过程的多次破坏产生的有价值的表型数据集，并深入了解了配子发生和胚胎发育都需要哪些基因，因此这些基因可能在胚胎缺陷突变体的筛选中未被检测到。
