Marmagne Anne, Chardon Fabien, Masclaux-Daubresse Céline
Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), 78000 Versailles, France.
Plant Physiol. 2024 Dec 23;197(1). doi: 10.1093/plphys/kiae647.
Autophagy is a vesicular mechanism that plays a fundamental role in nitrogen remobilization from senescing leaves to seeds. The Arabidopsis (Arabidopsis thaliana) autophagy (atg) mutants exhibit early senescence, reduced biomass, and low seed yield. The atg seeds also exhibit major changes in N and C concentrations. During plant development, autophagy genes are expressed in the source leaves and in the sink seeds during maturation. We thus addressed the question of whether the seed composition defects in atg mutants are caused by defective N remobilization from source leaves or whether they are due to the absence of autophagy in seeds during maturation. To answer this question, we restored autophagy activity in the atg5 mutant by expressing the wild-type (WT) ATG5 allele specifically in source leaves using the senescence-associated gene 12 (SAG12) promoter or specifically in seeds using the Glycinin-1 promoter, or in both organs using both constructs. In atg5, N remobilization from the rosettes to seeds was almost completely reestablished when transformed with the pSAG12::ATG5 construct. However, transformation with the pSAG12::ATG5 construct only partially restored seed composition. In contrast, seed N and C composition was largely restored by transformation with the pGly::ATG5 construct, even though the early leaf senescence phenotype was maintained in the atg5 background. Cotransformation with pSAG12::ATG5 and pGly::ATG5 completely restored the WT remobilization and seed composition phenotypes. Our results highlight the essential role of autophagy in leaves for nitrogen supply and in seeds for the establishment of carbon and nitrogen reserves.
自噬是一种囊泡机制，在衰老叶片中的氮素向种子的再转运过程中发挥着重要作用。拟南芥自噬（atg）突变体表现出早衰、生物量减少和种子产量低的现象。atg突变体种子的氮和碳浓度也有显著变化。在植物发育过程中，自噬基因在源叶中表达，在成熟过程中的库种子中也表达。因此，我们探讨了atg突变体种子组成缺陷是由源叶中氮再转运缺陷引起的，还是由于成熟过程中种子中缺乏自噬所致。为了回答这个问题，我们通过使用衰老相关基因12（SAG12）启动子在源叶中特异性表达野生型（WT）ATG5等位基因，或使用大豆球蛋白-1启动子在种子中特异性表达，或使用两种构建体在两个器官中表达，来恢复atg5突变体中的自噬活性。在atg5中，用pSAG12::ATG5构建体转化后，莲座叶向种子的氮再转运几乎完全恢复。然而，用pSAG12::ATG5构建体转化只能部分恢复种子组成。相比之下，用pGly::ATG5构建体转化可使种子的氮和碳组成在很大程度上恢复，尽管在atg5背景下仍维持早期叶片衰老表型。用pSAG12::ATG5和pGly::ATG5共转化完全恢复了野生型的再转运和种子组成表型。我们的结果突出了自噬在叶片中对氮供应以及在种子中对碳和氮储备建立的重要作用。
