Lothier Jérémy, Diab Houssein, Cukier Caroline, Limami Anis M, Tcherkez Guillaume
Seedling Metabolism and Stress, Université d'Angers, Agrocampus Ouest, INRAE, UMR IRHS, SFR QuaSaV, 49071 Beaucouzé, France.
Research School of Biology, ANU Joint College of Science, Australian National University, Canberra 2601, ACT, Australia.
Plants (Basel). 2020 Oct 15;9(10):1373. doi: 10.3390/plants9101373.
Root oxygen deficiency that is induced by flooding (waterlogging) is a common situation in many agricultural areas, causing considerable loss in yield and productivity. Physiological and metabolic acclimation to hypoxia has mostly been studied on roots or whole seedlings under full submergence. The metabolic difference between shoots and roots during waterlogging, and how roots and shoots communicate in such a situation is much less known. In particular, the metabolic acclimation in shoots and how this, in turn, impacts on roots metabolism is not well documented. Here, we monitored changes in the metabolome of roots and shoots of barrel clover (), growth, and gas-exchange, and analyzed phloem sap exudate composition. Roots exhibited a typical response to hypoxia, such as γ-aminobutyrate and alanine accumulation, as well as a strong decline in raffinose, sucrose, hexoses, and pentoses. Leaves exhibited a strong increase in starch, sugars, sugar derivatives, and phenolics (tyrosine, tryptophan, phenylalanine, benzoate, ferulate), suggesting an inhibition of sugar export and their alternative utilization by aromatic compounds production via pentose phosphates and phosphopyruvate. Accordingly, there was an enrichment in sugars and a decline in organic acids in phloem sap exudates under waterlogging. Mass-balance calculations further suggest an increased imbalance between loading by shoots and unloading by roots under waterlogging. Taken as a whole, our results are consistent with the inhibition of sugar import by waterlogged roots, leading to an increase in phloem sugar pool, which, in turn, exert negative feedback on sugar metabolism and utilization in shoots.
由洪涝（渍水）引起的根系缺氧在许多农业地区是一种常见情况，会导致产量和生产力大幅损失。对缺氧的生理和代谢适应性大多是在完全淹没条件下对根系或整株幼苗进行研究的。渍水期间地上部和根系之间的代谢差异，以及在这种情况下根系和地上部如何进行交流则鲜为人知。特别是，地上部的代谢适应性以及这如何反过来影响根系代谢，目前尚无充分记录。在这里，我们监测了红三叶根系和地上部的代谢组变化、生长及气体交换，并分析了韧皮部汁液渗出物的成分。根系表现出对缺氧的典型反应，如γ-氨基丁酸和丙氨酸积累，以及棉子糖、蔗糖、己糖和戊糖的大幅下降。叶片中的淀粉、糖类、糖衍生物和酚类物质（酪氨酸、色氨酸、苯丙氨酸、苯甲酸、阿魏酸）大幅增加，这表明糖类输出受到抑制，并且它们通过戊糖磷酸途径和磷酸丙酮酸被用于芳香族化合物生产的替代利用。因此，渍水条件下韧皮部汁液渗出物中的糖类富集而有机酸减少。质量平衡计算进一步表明，渍水条件下地上部装载和根系卸载之间的不平衡加剧。总体而言，我们的结果与渍水根系对糖类输入的抑制一致，导致韧皮部糖库增加，进而对地上部的糖代谢和利用产生负反馈。
