A proposed role for endomembrane trafficking processes in regulating tonoplast content and vacuole dynamics under ammonium stress conditions in Arabidopsis root cells

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.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Robert, German. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Robert, German. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Robert, German. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal; ArgentinaFil: Yagyu, Mako. Meiji University. School of Agriculture. Department of Life Sciences; JapónFil: Lascano, Hernán Ramiro. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal; ArgentinaFil: Lascano, Hernán Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Lascano, Hernán Ramiro. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales. ArgentinaFil: Masclaux-Daubresse, Céline. Université Paris-Saclay. AgroParisTech. Institut Jean-Pierre Bourgin. FranciaFil: Yoshimoto, Kohki. Meiji University. School of Agriculture. Department of Life Sciences; Japó