Ferri Alessandro, Lancilli Clarissa, Maghrebi Moez, Lucchini Giorgio, Sacchi Gian Attilio, Nocito Fabio F
Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli Studi di MilanoMilano, Italy.
Istituto d'Istruzione Superiore di CodognoCodogno, Italy.
Front Plant Sci. 2017 May 22;8:854. doi: 10.3389/fpls.2017.00854. eCollection 2017.
The processes involved in cadmium detoxification in plants deeply affect sulfate uptake and thiol homeostasis and generate increases in the plant nutritional request for sulfur. Here, we present an analysis of the dependence of Arabidopsis growth on the concentration of sulfate in the growing medium with the aim of providing evidence on how plants optimize growth at a given sulfate availability. Results revealed that short-term (72 h) exposure to a broad range of Cd concentrations (0.1, 1, and 10 μM) inhibited plant growth but did not produce any significant effects on the growth pattern of both shoots and roots in relation to the external sulfate. Conversely, long-term (22 days) exposure to 0.1 μM Cd significantly changed the pattern of fresh weight accumulation of the shoots in relation to the external sulfate, without affecting that of the roots, although their growth was severely inhibited by Cd. Moreover, under long-term exposure to Cd, increasing the sulfate external concentration up to the critical value progressively reduced the inhibitory effects exerted by Cd on shoot growth, indicating the existence of sulfate-dependent adaptive responses protecting the shoot tissues against Cd injury. Transcriptional induction of the high-affinity sulfate transporter genes ( and ) involved in sulfate uptake by roots was a common adaptive response to both short- and long-term exposure to Cd. Such a response was closely related to the total amount of non-protein thiols accumulated by a single plant under short-term exposure to Cd, but did not showed any clear relation with thiols under long-term exposure to Cd. In this last condition, Cd exposure did not change the level of non-protein thiols per plant and thus did not alter the nutritional need for sulfur. In conclusion, our results indicate that long term-exposure to Cd, although it induces sulfate uptake, decreases the capacity of the Arabidopsis roots to efficiently absorb the sulfate ions available in the growing medium making the adaptive response of and "" not enough to optimize the growth at sulfate external concentrations lower than the critical value.
植物中镉解毒所涉及的过程深刻影响硫酸盐吸收和硫醇稳态，并导致植物对硫的营养需求增加。在此，我们分析了拟南芥生长对生长培养基中硫酸盐浓度的依赖性，旨在提供关于植物如何在给定的硫酸盐可利用性条件下优化生长的证据。结果表明，短期（72小时）暴露于广泛的镉浓度（0.1、1和10 μM）会抑制植物生长，但对地上部和根部相对于外部硫酸盐的生长模式没有产生任何显著影响。相反，长期（22天）暴露于0.1 μM镉会显著改变地上部相对于外部硫酸盐的鲜重积累模式，而不影响根部的模式，尽管根部生长受到镉的严重抑制。此外，在长期暴露于镉的情况下，将外部硫酸盐浓度提高到临界值会逐渐降低镉对地上部生长的抑制作用，表明存在依赖硫酸盐的适应性反应，保护地上部组织免受镉伤害。参与根部硫酸盐吸收的高亲和力硫酸盐转运蛋白基因（和）的转录诱导是对短期和长期暴露于镉的常见适应性反应。这种反应与短期暴露于镉的单株植物积累的非蛋白硫醇总量密切相关，但与长期暴露于镉的硫醇没有明显关系。在最后这种情况下，镉暴露不会改变单株植物的非蛋白硫醇水平，因此不会改变对硫的营养需求。总之，我们的结果表明，长期暴露于镉虽然会诱导硫酸盐吸收，但会降低拟南芥根部有效吸收生长培养基中可用硫酸根离子的能力，使得和的适应性反应不足以在低于临界值的外部硫酸盐浓度下优化生长。
