James Maxence, Trouverie Jacques, Marmagne Anne, Chardon Fabien, Frémont Julie, Etienne Philippe, Masclaux-Daubresse Céline
Université de Caen Normandie, UNICAEN, INRAE, UMR 950 EVA, SFR Normandie Végétal (FED4277), 14000 Caen, France.
Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin for Plant Sciences (IJPB), 78000 Versailles, France.
Ann Bot. 2025 Jun 4. doi: 10.1093/aob/mcaf050.
Macroautophagy is essential for the degradation and recycling of various macromolecules in eukaryote cells. In plants, autophagy is involved in the degradation of damaged chloroplasts in response to stress. Autophagy is a key player in nitrogen management at the whole-plant level, and autophagy mutants display strong defects in nitrogen remobilization and early leaf senescence phenotypes especially under nitrogen source limitation. It is known that leaf senescence is associated to nutrient remobilization processes and is induced by nitrate limitation. However, it remains to be determined which actors are involved in this interplay and whether nutrient remobilization acts as a signal that enhances leaf senescence or whether senescence-associated chloroplast degradation promotes nutrient remobilization. In this context, our aim is to demine whether the level of autophagy activity controls leaf longevity and influences the progress of leaf senescence balancing resources and waste management.
In this study, we used Arabidopsis autophagy knock-out mutants (atg) and plants overexpressing autophagy associated genes (ATG8-OE) to compare their phenotypes to wild type under both sufficient nitrate condition and nitrate starvation.
The transfer from nitrate-sufficient conditions to nitrate starvation accelerated leaf senescence in all the genotypes. Unexpectedly, under both sufficient and nitrate-starved conditions, both atg mutants and ATG8 over-expressors exhibited earlier leaf senescence phenotypes compared to wild type. Given that autophagy is a longevity factor, the more severe leaf senescence phenotype of over-expressors was puzzling. This study highlights a relationship between autophagy, nitrogen remobilization and leaf senescence and shows how the fine tuning of nutrient management can influence senescence onset.
The fine-tuning of autophagy is necessary to control leaf senescence.
巨自噬对于真核细胞中各种大分子的降解和循环利用至关重要。在植物中，自噬参与了应激条件下受损叶绿体的降解。自噬是全株水平氮素管理的关键参与者，自噬突变体在氮素再利用和早期叶片衰老表型方面表现出强烈缺陷，尤其是在氮源限制条件下。已知叶片衰老与养分再利用过程相关，且受硝酸盐限制诱导。然而，仍有待确定哪些因素参与了这种相互作用，以及养分再利用是否作为一种信号增强叶片衰老，或者衰老相关的叶绿体降解是否促进养分再利用。在此背景下，我们的目的是确定自噬活性水平是否控制叶片寿命，并影响叶片衰老进程，以平衡资源和废物管理。
在本研究中，我们使用拟南芥自噬敲除突变体（atg）和过表达自噬相关基因的植物（ATG8 - OE），在充足硝酸盐条件和硝酸盐饥饿条件下，将它们的表型与野生型进行比较。
从硝酸盐充足条件转变为硝酸盐饥饿条件加速了所有基因型的叶片衰老。出乎意料的是，在充足和硝酸盐饥饿条件下，与野生型相比，atg突变体和ATG8过表达体均表现出更早的叶片衰老表型。鉴于自噬是一个寿命因子，过表达体更严重的叶片衰老表型令人费解。本研究突出了自噬、氮素再利用和叶片衰老之间的关系，并展示了养分管理的微调如何影响衰老的起始。
自噬的微调对于控制叶片衰老至关重要。
