Chloroplast biogenesis requires the coordinated expression of the chloroplast and nuclear genomes, which is achieved by communication between the developing chloroplasts and the nucleus. Signals emitted from the plastids, so-called retrograde signals, control nuclear gene expression depending on plastid development and functionality. Genetic analysis of this pathway identified a set of mutants defective in retrograde signaling and designated genomes uncoupled (gun) mutants. Subsequent research has pointed to a significant role of tetrapyrrole biosynthesis in retrograde signaling. Meanwhile, the molecular functions of GUN1, the proposed integrator of multiple retrograde signals, have not been identified yet. However, based on the interactions of GUN1, some working hypotheses have been proposed. Interestingly, GUN1 contributes to important biological processes, including plastid protein homeostasis, through transcription, translation, and protein import. Furthermore, the interactions of GUN1 with tetrapyrroles and their biosynthetic enzymes have been revealed. This review focuses on our current understanding of the function of tetrapyrrole retrograde signaling on chloroplast biogenesis.

中文翻译：

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四环吡咯和GUN1依赖信号在叶绿体生物发生中的作用

叶绿体生物发生需要叶绿体和核基因组的协调表达，这是通过发育中的叶绿体和细胞核之间的通讯来实现的。从质体发出的信号，即所谓的逆行信号，取决于质体的发育和功能来控制核基因的表达。该途径的遗传分析确定了一组逆向信号缺陷的突变体，并且指定的基因组未偶联（枪）的突变体。随后的研究指出了四吡咯生物合成在逆行信号中的重要作用。同时，尚未确定拟议的多个逆行信号的整合者GUN1的分子功能。但是，基于GUN1的相互作用，提出了一些可行的假设。有趣的是，GUN1通过转录，翻译和蛋白质导入，促进了重要的生物学过程，包括质体蛋白质稳态。此外，已经揭示了GUN1与四吡咯及其生物合成酶的相互作用。这篇综述集中在我们目前对四吡咯逆行信号在叶绿体生物发生中的功能的理解。