GUN1 (genomes uncoupled 1), a chloroplast-localized pentatricopeptide repeat (PPR) protein with a C-terminal small mutS-related (SMR) domain, plays a central role in the retrograde communication of chloroplasts with the nucleus. This flow of information is required for the coordinated expression of plastid and nuclear genes, and it is essential for the correct development and functioning of chloroplasts. Multiple genetic and biochemical findings indicate that GUN1 is important for protein homeostasis in the chloroplast; however, a clear and unified view of GUN1′s role in the chloroplast is still missing. Recently, GUN1 has been reported to modulate the activity of the nucleus-encoded plastid RNA polymerase (NEP) and modulate editing of plastid RNAs upon activation of retrograde communication, revealing a major role of GUN1 in plastid RNA metabolism. In this opinion article, we discuss the recently identified links between plastid RNA metabolism and retrograde signaling by providing a new and extended concept of GUN1 activity, which integrates the multitude of functional genetic interactions reported over the last decade with its primary role in plastid transcription and transcript editing.

中文翻译：

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GUN1和质体RNA代谢：遗传学

GUN1（基因组未偶联1）是叶绿体定位的五肽重复序列（PPR）蛋白，具有C端小mutS相关（SMR）域，在叶绿体与细胞核逆行通信中起着核心作用。这种信息流是质体和核基因协调表达所必需的，对于叶绿体的正确发育和功能至关重要。多种遗传和生化发现表明，GUN1对于叶绿体中的蛋白质稳态非常重要。但是，仍然缺少关于GUN1在叶绿体中作用的清晰统一的看法。最近，据报道，GUN1可调节核编码质体RNA聚合酶（NEP）的活性，并在激活逆行通讯时调节质体RNA的编辑，揭示了GUN1在质体RNA代谢中的主要作用。在这篇见解文章中，我们通过提供新的和扩展的GUN1活性概念来讨论最近发现的质体RNA代谢和逆行信号之间的联系，该概念将过去十年中报道的众多功能性遗传相互作用与其在质体转录和表达中的主要作用整合在一起。成绩单编辑。