ABSTRACT

Ammonium (NH₄⁺) stress has multiple effects on plant physiology, therefore, plant responses are complex, and multiple mechanisms are involved in NH₄⁺ sensitivity and tolerance in plants. Root growth inhibition is an important quantitative readout of the effects of NH₄⁺ stress on plant physiology, and cell elongation appear as the principal growth inhibition target. We recently proposed autophagy as a relevant physiological mechanisms underlying NH₄⁺ sensitivity response in Arabidopsis. In a brief overview, the impaired macro-autophagic flux observed under NH₄⁺ stress conditions has a detrimental impact on the cellular energetic balance, and therefore on the energy-demanding plant growth. In contrast to its inhibitory effect on the autophagosomes flux to vacuole, NH₄⁺ toxicity induced a micro-autophagy-like process. Consistent with the reduced membrane flux to the vacuole related to macro-autophagy inhibition and the increased tonoplast degradation due to enhanced micro-autophagy, the vacuoles of the root cells of the NH₄⁺-stressed plants showed lower tonoplast content and a decreased perimeter/area ratio. As the endosome-to-vacuole trafficking is another important process that contributes to membrane flux toward the vacuole, we evaluated the effects of NH₄⁺ stress on this process. This allows us to propose that autophagy could contribute to vacuole development as well as possible avenues to follow for future studies.

摘要

铵(NH ₄ ^{+ )胁迫对植物生理具有多重影响，因此植物反应复杂，植物对NH} ₄ ⁺的敏感性和耐受性涉及多种机制。根系生长抑制是NH ₄ ⁺胁迫对植物生理影响的重要定量指标，细胞伸长是主要的生长抑制目标。_{我们最近提出自噬作为拟南芥NH 4} ⁺敏感性反应的相关生理机制。简而言之，在 NH ₄ ^{+下观察到的大自噬通量受损}压力条件对细胞能量平衡有不利影响，因此对能量需求的植物生长也有不利影响。与其对自噬体流向液泡的抑制作用相反，NH ₄ ⁺毒性诱导了类似微自噬的过程。与大自噬抑制相关的液泡膜通量减少和微自噬增强导致液泡膜降解增加一致，NH ₄ ⁺胁迫植物根细胞液泡的液泡膜含量较低，周长/面积比。由于内体到液泡的运输是另一个有助于膜向液泡流动的重要过程，我们评估了 NH ₄ ⁺强调这个过程。这使我们能够提出自噬可能有助于液泡发育以及未来研究的可能途径。