Fitter David W, Martin David J, Copley Martin J, Scotland Robert W, Langdale Jane A
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
Plant J. 2002 Sep;31(6):713-27. doi: 10.1046/j.1365-313x.2002.01390.x.
Chloroplast biogenesis is a complex process that requires close co-ordination between two genomes. Many of the proteins that accumulate in the chloroplast are encoded by the nuclear genome, and the developmental transition from proplastid to chloroplast is regulated by nuclear genes. Here we show that a pair of Golden 2-like (GLK) genes regulates chloroplast development in Arabidopsis. The GLK proteins are members of the GARP superfamily of transcription factors, and phylogenetic analysis demonstrates that the maize, rice and Arabidopsis GLK gene pairs comprise a distinct group within the GARP superfamily. Further phylogenetic analysis suggests that the gene pairs arose through separate duplication events in the monocot and dicot lineages. As in rice, AtGLK1 and AtGLK2 are expressed in partially overlapping domains in photosynthetic tissue. Insertion mutants demonstrate that this expression pattern reflects a degree of functional redundancy as single mutants display normal phenotypes in most photosynthetic tissues. However, double mutants are pale green in all photosynthetic tissues and chloroplasts exhibit a reduction in granal thylakoids. Products of several genes involved in light harvesting also accumulate at reduced levels in double mutant chloroplasts. GLK genes therefore regulate chloroplast development in diverse plant species.
叶绿体生物发生是一个复杂的过程，需要两个基因组之间密切协调。许多在叶绿体中积累的蛋白质由核基因组编码，从前质体到叶绿体的发育转变受核基因调控。在这里，我们表明一对类Golden 2（GLK）基因调控拟南芥中的叶绿体发育。GLK蛋白是转录因子GARP超家族的成员，系统发育分析表明，玉米、水稻和拟南芥的GLK基因对在GARP超家族中构成一个独特的类群。进一步的系统发育分析表明，这些基因对是通过单子叶植物和双子叶植物谱系中各自的复制事件产生的。与水稻一样，AtGLK1和AtGLK2在光合组织中部分重叠的区域表达。插入突变体表明，这种表达模式反映了一定程度的功能冗余，因为单个突变体在大多数光合组织中表现出正常表型。然而，双突变体在所有光合组织中呈淡绿色，叶绿体中的基粒类囊体减少。参与光捕获的几个基因的产物在双突变体叶绿体中的积累水平也降低。因此，GLK基因调控多种植物物种中的叶绿体发育。
