Instituto de Química y Fisicoquímica Biológicas Dr Alejandro Paladini (IQUIFIB), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
Universidad de Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina.
Ecotoxicol Environ Saf. 2020 Mar 15;191:110163. doi: 10.1016/j.ecoenv.2020.110163. Epub 2020 Jan 14.
The purpose of the present work was to study the effect of the nitrogen source (NO vs NH) on cadmium (Cd) uptake, translocation and partition and its associated toxicity in hydroponically-grown Arabidopsis plants. After a short growth period on a complete Hoagland nutrient solution, Arabidopsis seedlings continued in the same growth medium (NA) or were switched to NO (N) or NH (A) as sole N sources and supplied with 2.5 μM Cd. Unrelated to the nitrogen source, Cd reached higher levels in roots than in leaves. However, when ammonium was the source of nitrogen, Cd accumulation in roots was lower than in N or NA medium and the metal translocation to the aerial part was restricted, reaching values 25%-35% below the levels observed in plants grown with N or NA. Cadmium negatively affected chlorophyll content and PSII quantum yield, independently of the nitrogen source, with the highest decrease (35%) under NA treatment. Proline content increased, either with NA, N or A supplied in the presence of Cd, whereas a rise in total anthocyanin content was clearly favored when ammonium was the source of nitrogen, with or without Cd. In leaves, while NIA1 and NIA2 expression was markedly reduced by Cd in the presence of N or NA, ammonium source slightly reduced NIA1 expression but greatly upregulated NIA2 expression upon Cd exposure. The decay in NR activity was independent of the nitrogen source when Cd was applied and this decay was accompanied by a great increase in NH levels either with nitrates or ammonium in the medium in the presence of Cd. Only NIA1 was detected in roots and its expression, together with NR activity and nitrates levels, was the highest in N medium devoid of Cd. The possibility of reducing Cd health risks through nitrogen fertilization practices is discussed.
本研究旨在探讨氮源（硝态氮与铵态氮）对镉吸收、转运和分配的影响及其与镉毒性的关系。在完全 Hoagland 营养液中生长一段时间后，拟南芥幼苗继续在相同的生长介质（NA）中生长，或切换为仅含硝态氮（N）或铵态氮（A）的生长介质，并添加 2.5 μM 的镉。与氮源无关，镉在根部的积累量高于叶片。然而，当铵态氮为氮源时，根部的镉积累量低于 N 或 NA 培养基中的镉积累量，且金属向地上部分的转运受到限制，转运量比用 N 或 NA 培养的植物低 25%-35%。镉对叶绿素含量和 PSII 量子产率均有负面影响，而氮源对其无影响，在 NA 处理下下降幅度最大（35%）。脯氨酸含量增加，无论是在有镉的情况下用 NA、N 还是 A 作为氮源，还是在有或没有镉的情况下，当铵态氮为氮源时，总花青素含量明显增加。在叶片中，当 N 或 NA 培养基中存在镉时，NIA1 和 NIA2 的表达明显受到抑制，但当存在镉时，铵态氮源会轻微降低 NIA1 的表达，但会大大上调 NIA2 的表达。NR 活性的衰减与氮源无关，当施加镉时，这种衰减伴随着 NH 水平的大幅增加，无论是在有硝酸盐还是铵盐的培养基中。在根部只检测到 NIA1，其表达水平以及 NR 活性和硝酸盐水平在不含镉的 N 培养基中最高。本文讨论了通过氮施肥实践降低镉健康风险的可能性。
