Dissection of the tetrapyrrole-mediated signaling pathway: Identification of components involved in signal transduction and of target genes

控制必需的四吡咯生物合成需要逆行信号转导。对全球转录谱的组合分析和对叶绿素合成分支中酶的相互作用伙伴的鉴定表明：(I)化学诱导的四吡咯生物合成基因表达的解除是识别早期上调和下调基因的直接策略，(Ii)酶的解除表达而不是特定的镁卟啉的积累影响核基因的表达，以及(Iii)确定的相互作用伙伴可能有助于叶绿体中产生的不同逆行信号的组合。该项目旨在证实四吡咯途径介导的信号转导机制。经过基因芯片和生物信息学分析的评估，确定了目的基因，并提出了该信号通路的新成分。在转基因品系中，将通过RNAi失活和过度表达来分析它们对逆行信号的贡献。同时，将对四吡咯代谢物和效应物的影响进行强有力的比较分析，并与光自养拟南芥细胞培养进行比较。将继续使用表达标记蛋白的转化子对叶绿素合成分支的酶的蛋白质复合体进行精细分析，以揭示它们对四吡咯生物合成途径的控制和信号传递的贡献。预计将有新的见解，从而能够对四吡咯代谢如何整合到叶绿体来源的逆行信号中进行实质性评估。

Control of the essential tetrapyrrole biosynthesis requires retrograde signaling. Combinatorial analyses of global transcript profiles and identification of interaction partners of enzymes in the chlorophyll-synthesizing branch revealed that (I) chemically induced deregulation of expression of tetrapyrrole biosynthesis genes is a straight forward strategy to identify early up- and downregulated genes, (II) deregulated expression of enzymes rather than accumulation of specific Mg porphyrins affects nuclear gene expression, and (III) identified interaction partners likely contribute to the combination of different retrograde signals generated in plastids. The project aims to substantiate the mechanisms of tetrapyrrole pathway-mediated signaling. After evaluation of microarray and bioinformatics analyses target genes are identified and new components of the signaling pathway are proposed. Their contribution to retrograde signaling will be analyzed in transgenic lines by RNAi inactivation and overexpression. In parallel, a robust comparative analysis of the impact of tetrapyrrolic metabolites and effectors will be performed with photoautotrophic Arabidopsis cell cultures. Refined analyses of protein complexes for enzymes of the chlorophyll synthesis branch will be continued using transformants expressing tagged-proteins to reveal their contribution to control and signaling of the tetrapyrrole biosynthetic pathway. New insights are expected allowing a substantial assessment how tetrapyrrole metabolism is integrated in plastid-derived retrograde signaling.