Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
Mol Plant. 2012 Jul;5(4):901-13. doi: 10.1093/mp/ssr112. Epub 2011 Dec 26.
The presence of genes encoding organellar proteins in different cellular compartments necessitates a tight coordination of expression by the different genomes of the eukaryotic cell. This coordination of gene expression is achieved by organelle-to-nucleus or retrograde communication. Stress-induced perturbations of the tetrapyrrole pathway trigger large changes in nuclear gene expression in plants. Recently, we identified HSP90 proteins as ligands of the putative plastid signal Mg-ProtoIX. In order to investigate whether the interaction between HSP90 and Mg-ProtoIX is biologically relevant, we produced transgenic lines with reduced levels of cytosolic HSP90 in wild-type and gun5 backgrounds. Our work reveals that HSP90 proteins respond to the tetrapyrrole-mediated plastid signal to control expression of photosynthesis-associated nuclear genes (PhANG) during the response to oxidative stress. We also show that the hy5 mutant is insensitive to tetrapyrrole accumulation and that Mg-ProtoIX, cytosolic HSP90, and HY5 are all part of the same signaling pathway. These findings suggest that a regulatory complex controlling gene expression that includes HSP90 proteins and a transcription factor that is modified by tetrapyrroles in response to changes in the environment is evolutionarily conserved between yeast and plants.
细胞器蛋白基因存在于不同的细胞区室中，这就需要真核细胞的不同基因组之间进行紧密的表达协调。这种基因表达的协调是通过细胞器到细胞核或逆行通讯来实现的。植物中四吡咯途径的应激诱导扰动会触发核基因表达的大量变化。最近，我们鉴定了 HSP90 蛋白作为假定质体信号 Mg-ProtoIX 的配体。为了研究 HSP90 和 Mg-ProtoIX 之间的相互作用是否具有生物学相关性，我们在野生型和 gun5 背景下产生了细胞质 HSP90 水平降低的转基因系。我们的工作表明，HSP90 蛋白响应四吡咯介导的质体信号，在应对氧化应激时控制光合作用相关核基因（PhANG）的表达。我们还表明，hy5 突变体对四吡咯积累不敏感，并且 Mg-ProtoIX、细胞质 HSP90 和 HY5 都是同一信号通路的一部分。这些发现表明，一个包括 HSP90 蛋白和转录因子的调控复合物，该转录因子通过四吡咯的修饰来响应环境变化，在酵母和植物之间是保守的。
