Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan.
J Plant Physiol. 2011 Nov 1;168(16):1987-92. doi: 10.1016/j.jplph.2011.06.001. Epub 2011 Jul 14.
We previously reported that native tropical zone plants showed high acetylcholinesterase (AChE) activity during heat stress, and that AChE activity in endodermal cells of maize seedlings was increased by heat treatment. However, the physiological role of AChE in heat stressed plants is still unclear. Here we report (1) tissue-specific expression and subcellular localization of maize AChE, (2) elevation of AChE activity and possible post-translational modifications of this enzyme under heat stress, and (3) involvement of AChE in plant heat stress tolerance. Maize AChE was mainly expressed in coleoptile nodes and seeds. Maize AChE fused with green fluorescent protein (GFP) was localized in extracellular spaces of transgenic rice plants. Therefore, in maize coleoptile nodes and seeds AChE mainly functions in the cell wall matrix. After heat treatment, enhanced maize AChE activity was observed by in vitro activity measurement and by in situ cytochemical staining; transcript and protein levels, however, were not changed. Protein gel blot analysis revealed two AChE isoforms (upper and lower); the upper-form gradually disappeared after heat treatment. Thus, maize AChE activity might be enhanced through a post-translational modification response to heat stress. Finally, we found that overexpression of maize AChE in transgenic tobacco plants enhanced heat tolerance relative to that of non-transgenic plants, suggesting AChE plays a positive role in maize heat tolerance.
我们之前曾报道过，热带地区的植物在受到热胁迫时表现出较高的乙酰胆碱酯酶（AChE）活性，而玉米幼苗的内胚层细胞的 AChE 活性会因热处理而增加。然而，AChE 在受热胁迫植物中的生理作用仍不清楚。在这里，我们报道了（1）玉米 AChE 的组织特异性表达和亚细胞定位，（2）在热胁迫下 AChE 活性的升高和可能的翻译后修饰，以及（3）AChE 参与植物耐热性。玉米 AChE 主要在胚芽鞘节和种子中表达。与绿色荧光蛋白（GFP）融合的玉米 AChE 定位于转基因水稻植株的细胞外空间。因此，在玉米胚芽鞘节和种子中，AChE 主要在细胞壁基质中发挥作用。经过热处理后，通过体外活性测定和原位细胞化学染色观察到增强的玉米 AChE 活性；然而，转录物和蛋白质水平没有变化。蛋白质凝胶电泳分析显示存在两种 AChE 同工型（上和下）；上形式在热处理后逐渐消失。因此，玉米 AChE 活性可能通过对热应激的翻译后修饰反应得到增强。最后，我们发现，在转基因烟草植物中过表达玉米 AChE 可提高其耐热性，相对非转基因植物而言，这表明 AChE 在玉米耐热性中发挥积极作用。
