Liu Yuankun, Tao Qi, Li Jinxing, Guo Xinyu, Luo Jipeng, Jupa Radek, Liang Yongchao, Li Tingqiang
Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmentaland Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
College of Resources, Sichuan Agricultural University, Chengdu, 611130, China.
J Hazard Mater. 2021 Feb 5;403:123729. doi: 10.1016/j.jhazmat.2020.123729. Epub 2020 Aug 19.
Ethylene is an important phytohormone for plant adaptation to heavy metal stress. However, the effects of ethylene on radial apoplastic transport of Cd remain elusive. This study investigated the role of ethylene on apoplastic barriers development and consequences for Cd uptake in Sedum alfredii. In response to Cd, endogenous ethylene production in hyperaccumulating ecotype (HE) roots was decreased due to the down-regulated expressions of ethylene biosynthesis genes, while the opposite result was observed in non-hyperaccumulating ecotype (NHE). Interestingly, the ethylene emission in HE was always higher than that in NHE, regardless of Cd concentrations. Results of exogenous application of ethylene biosynthesis precursor/inhibitor indicate that ethylene with high level would delay the formation of apoplastic barriers in HE through restraining phenylalanine ammonia lyase activity and gene expressions related to lignin/suberin biosynthesis. Simultaneously, correlation analyses suggest that Cd-induced apoplastic barriers formation may be also regulated by ethylene signaling. By using an apoplastic bypass tracer and scanning ion-selected electrode, we observed that the delayed deposition of apoplastic barriers significantly promoted Cd influx in roots. Taken together, high endogenous ethylene in HE postponed the formation of apoplastic barriers and thus promoted the Cd accumulation in the apoplast of roots.
乙烯是植物适应重金属胁迫的一种重要植物激素。然而，乙烯对镉径向质外体运输的影响仍不清楚。本研究调查了乙烯在东南景天质外体屏障发育中的作用以及对镉吸收的影响。响应镉胁迫，超积累生态型（HE）根中内源性乙烯产量因乙烯生物合成基因表达下调而降低，而非超积累生态型（NHE）则观察到相反的结果。有趣的是，无论镉浓度如何，HE中的乙烯释放量总是高于NHE。乙烯生物合成前体/抑制剂的外源应用结果表明，高水平的乙烯会通过抑制苯丙氨酸解氨酶活性以及与木质素/木栓质生物合成相关的基因表达，延迟HE中质外体屏障的形成。同时，相关性分析表明，镉诱导的质外体屏障形成也可能受乙烯信号调控。通过使用质外体旁路示踪剂和扫描离子选择电极，我们观察到质外体屏障的延迟沉积显著促进了根中镉的流入。综上所述，HE中高内源性乙烯延缓了质外体屏障的形成，从而促进了根质外体中镉的积累。
