Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou 310058, China.
J Exp Bot. 2012 May;63(8):3127-36. doi: 10.1093/jxb/ers036. Epub 2012 Feb 29.
Nitrogen (N) management is a promising agronomic strategy to minimize cadmium (Cd) contamination in crops. However, it is unclear how N affects Cd uptake by plants. Wild-type and iron uptake-inefficient tomato (Solanum lycopersicum) mutant (T3238fer) plants were grown in pH-buffered hydroponic culture to investigate the direct effect of N-form on Cd uptake. Wild-type plants fed NO₃⁻ accumulated more Cd than plants fed NH₄⁺. Iron uptake and LeIRT1 expression in roots were also greater in plants fed NO₃⁻. However, in mutant T3238fer which loses FER function, LeIRT1 expression in roots was almost completely terminated, and the difference between NO₃⁻ and NH₄⁺ treatments vanished. As a result, the N-form had no effect on Cd uptake in this mutant. Furthermore, suppression of LeIRT1 expression by NO synthesis inhibition with either tungstate or L-NAME, also substantially inhibited Cd uptake in roots, and the difference between N-form treatments was diminished. Considering all of these findings, it was concluded that the up-regulation of the Fe uptake system was responsible for NO₃⁻-facilitated Cd accumulation in plants.
氮素管理是一种有前途的农业策略，可以最大限度地减少作物中的镉污染。然而，目前尚不清楚氮素如何影响植物对镉的吸收。本研究采用 pH 缓冲水培培养的野生型和铁吸收效率低下的番茄（Solanum lycopersicum）突变体（T3238fer）植株，以研究氮形态对镉吸收的直接影响。与铵态氮（NH₄⁺）处理相比，施硝态氮（NO₃⁻）的野生型植株积累了更多的镉。同时，NO₃⁻处理的植株根系铁吸收和 LeIRT1 表达也更高。然而，在丧失 FER 功能的突变体 T3238fer 中，LeIRT1 表达几乎完全终止，NO₃⁻和 NH₄⁺处理之间的差异消失。因此，氮形态对该突变体的镉吸收没有影响。此外，用钨酸钠或 L-NAME 抑制硝酸盐合成抑制 LeIRT1 表达，也显著抑制了根中的镉吸收，并且氮形态处理之间的差异减小。综合所有这些发现，可以得出结论，铁吸收系统的上调是硝态氮促进植物镉积累的原因。
