Uwer U, Willmitzer L, Altmann T
Institut für Genbiologische Forschung, Ihnestrasse 63, 14195 Berlin, Germany.
Plant Cell. 1998 Aug;10(8):1277-94. doi: 10.1105/tpc.10.8.1277.
Embryo formation is the first patterning process during vegetative plant growth. Using transposons as insertional mutagens in Arabidopsis, we identified the mutant edd1 that shows embryo-defective development. The insertion mutation is lethal, arresting embryo growth between the globular and heart stages of embryonic development. The mutant phenotype cosegregates with a transposed Dissociation element. Sequences flanking the transposed element were isolated and used to isolate a full-length cDNA clone representing the wild-type EDD1 gene. Complementation of the mutant through Agrobacterium-mediated gene transfer of an EDD1 wild-type copy as well as loss of the transposon concomitant with phenotypic reversion demonstrated that the transposon had caused the mutation. Based on homology to Escherichia coli, the EDD1 gene is predicted to encode a novel glycyl-tRNA synthetase (GlyRS) that has not been identified previously in higher plants. An N-terminal portion of the plant protein is able to direct a marker protein into pea chloroplasts. Thus, the gene identified by the embryo-defective insertion mutation encodes a GlyRS homolog, probably acting within the plastidic compartment.
胚胎形成是植物营养生长过程中的首个模式形成过程。利用转座子作为拟南芥中的插入诱变剂，我们鉴定出了表现出胚胎发育缺陷的突变体edd1。插入突变是致死性的，会使胚胎发育在球状期和心形期之间停止生长。突变体表型与转座的解离元件共分离。分离出转座元件侧翼的序列，并用于分离代表野生型EDD1基因的全长cDNA克隆。通过农杆菌介导的EDD1野生型拷贝基因转移对突变体进行互补，以及转座子的缺失伴随表型回复，证明了转座子导致了该突变。基于与大肠杆菌的同源性，预测EDD1基因编码一种新型甘氨酰-tRNA合成酶（GlyRS），此前在高等植物中尚未鉴定到。植物蛋白的N端部分能够将一种标记蛋白导入豌豆叶绿体。因此，通过胚胎缺陷插入突变鉴定出的基因编码一种GlyRS同源物，可能在质体区室中发挥作用。
