Autophagy is an evolutionarily conserved system for the degradation of intracellular components in eukaryotic organisms. Autophagy plays essential roles in preventing premature senescence and extending the longevity of vascular plants. However, the mechanisms and physiological roles of autophagy in preventing senescence in basal land plants are still obscure. Here, we investigated the functional roles of the autophagy-related gene PpATG3 from Physcomitrella patens and demonstrated that its deletion prevents autophagy. In addition, Ppatg3 mutant showed premature gametophore senescence and reduced protonema formation compared to wild-type (WT) plants under normal growth conditions. The abundance of nitrogen (N) but not carbon (C) differed significantly between Ppatg3 mutant and WT plants, as did relative fatty acid levels. In vivo protein localization indicated that PpATG3 localizes to the cytoplasm, and in vitro Y2H assays confirmed that PpATG3 interacts with PpATG7 and PpATG12. Plastoglobuli (PGs) accumulated in Ppatg3, indicating that the process that degrades damaged chloroplasts in senescent gametophore cells was impaired in this mutant. RNA-Seq uncovered a detailed, comprehensive set of regulatory pathways that were affected by the autophagy mutation. The autophagy-related gene PpATG3 is essential for autophagosome formation in P. patens. Our findings provide evidence that autophagy functions in N utilization, fatty acid metabolism and damaged chloroplast degradation under non-stress conditions. We identified differentially expressed genes in Ppatg3 involved in numerous biosynthetic and metabolic pathways, such as chlorophyll biosynthesis, lipid metabolism, reactive oxygen species removal and the recycling of unnecessary proteins that might have led to the premature senescence of this mutant due to defective autophagy. Our study provides new insights into the role of autophagy in preventing senescence to increase longevity in basal land plants.

中文翻译：

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对Ppatg3突变体的综合分析表明，自噬在Physcomitrella patens的配子体衰老中起重要作用。

自噬是真核生物中细胞内组分降解的进化保守系统。自噬在防止过早衰老和延长维管植物的寿命方面起着至关重要的作用。但是，自噬在防止基础陆生植物衰老中的机制和生理学作用仍然不清楚。在这里，我们调查了Physcomitrella patens自噬相关基因PpATG3的功能作用，并证明了其缺失阻止了自噬。此外，与正常生长条件下的野生型（WT）植物相比，Ppatg3突变体显示出过早的配体衰老和减少的前体形成。Ppatg3突变体和野生型植物之间的氮含量（N）而不是碳含量（C）显着不同，相对脂肪酸水平也是如此。体内蛋白质定位表明PpATG3定位于细胞质，而体外Y2H分析证实PpATG3与PpATG7和PpATG12相互作用。在Ppatg3中积累的球囊（PGs），表明在该突变体中降解降解衰老配体细胞中受损叶绿体的过程受到损害。RNA-Seq发现了一系列受自噬突变影响的详细，全面的调控途径。自噬相关基因PpATG3对于彭定康中自噬体的形成至关重要。我们的发现提供了证据，表明自噬在非胁迫条件下在氮利用，脂肪酸代谢和受损的叶绿体降解中起作用。我们在Ppatg3中鉴定了差异表达的基因，这些基因参与了许多生物合成和代谢途径，例如叶绿素的生物合成，脂质代谢，活性氧的去除和不必要蛋白质的回收，由于自噬缺陷，可能导致该突变体过早衰老。我们的研究为自噬在防止衰老增加基础陆生植物寿命方面的作用提供了新见解。