Coninx Laura, Smisdom Nick, Kohler Annegret, Arnauts Natascha, Ameloot Marcel, Rineau François, Colpaert Jan V, Ruytinx Joske
Centre for Environmental Sciences, Environmental Biology, Hasselt University, Diepenbeek, Belgium.
Biomedical Research Institute, Hasselt University, Diepenbeek, Belgium.
Front Microbiol. 2019 Oct 10;10:2251. doi: 10.3389/fmicb.2019.02251. eCollection 2019.
Ectomycorrhizal (ECM) fungi are important root symbionts of trees, as they can have significant effects on the nutrient status of plants. In polluted environments, particular ECM fungi can protect their host tree from Zn toxicity by restricting the transfer of Zn while securing supply of essential nutrients. However, mechanisms and regulation of cellular Zn homeostasis in ECM fungi are largely unknown, and it remains unclear how ECM fungi affect the Zn status of their host plants. This study focuses on the characterization of a ZIP (Zrt/IrtT-like protein) transporter, , in the ECM fungus , a common root symbiont of young pine trees. is predicted to encode a plasma membrane-located Zn importer. Heterologous expression of in yeast mutants with impaired Zn uptake resulted in a minor impact on cellular Zn accumulation and growth. The gene product showed a dual localization and was detected at the plasma membrane and perinuclear region. ZIP-family Zn uptake transporters did not show the potential to induce trehalase activity in yeast and to function as Zn sensors. In response to excess environmental Zn, gene expression analysis demonstrated a rapid but minor and transient decrease in transcript level. In ECM root tips, the gene is upregulated. Whether this regulation is due to limited Zn availability at the fungal-plant interface or to developmental processes is unclear. Altogether, our results suggest a function for in cellular Zn redistribution from the ER next to a putative role in Zn uptake in
外生菌根（ECM）真菌是树木重要的根系共生体，因为它们会对植物的养分状况产生重大影响。在污染环境中，特定的ECM真菌可以通过限制锌的转移同时确保必需养分的供应来保护其宿主树免受锌毒性的影响。然而，ECM真菌中细胞锌稳态的机制和调控在很大程度上尚不清楚，并且ECM真菌如何影响其宿主植物的锌状况仍不明确。本研究聚焦于ECM真菌（一种幼龄松树常见的根系共生体）中一个ZIP（Zrt/IrtT样蛋白）转运体的特性研究。预计该转运体编码一种位于质膜的锌导入蛋白。在锌吸收受损的酵母突变体中异源表达该转运体，对细胞锌积累和生长产生了较小的影响。该转运体基因产物表现出双重定位，在质膜和核周区域均有检测到。ZIP家族的锌吸收转运体在酵母中未显示出诱导海藻糖酶活性和作为锌传感器的潜力。响应过量的环境锌，基因表达分析表明该转运体转录水平迅速但轻微且短暂地下降。在ECM根尖中，该基因上调。尚不清楚这种调控是由于真菌 - 植物界面处锌可用性有限还是发育过程所致。总之，我们的结果表明该转运体在细胞锌从内质网重新分布中发挥作用，此外在锌吸收中可能也具有假定作用。
