Department of Biology, Faculty of Science, Ege University, Bornova, Izmır, Turkey.
Department of Biology, Faculty of Science, Ege University, Bornova, Izmır, Turkey.
J Plant Physiol. 2020 Oct;253:153250. doi: 10.1016/j.jplph.2020.153250. Epub 2020 Aug 7.
The endoplasmic reticulum (ER) is the main site of secretory protein production and folding and its homeostasis under environmental stress is vital for the maintenance of the protein secretory pathway. The loss of homeostasis and accumulation of unfolded proteins in the ER is referred to as ER stress. Although, γ-aminobutyric acid (GABA) is an important regulator of stress response in plants, its roles during ER stress remains unclear. This study investigated the involvement of GABA in the ER stress response of plants. For this, changes in GABA metabolism under ER stress was analysed in Arabidopsis thaliana, then to study the response of the ER-folding machinery, plants were treated with exogenous GABA under ER stress. The antibiotic tunicamycin, which inhibits N-glycosylation was used to specifically induce ER stress. This stress up-regulated the expression of five glutamate decarboxylase (GAD) genes except GAD2 and GABA content of A. thaliana plants increased with an increasing concentration of tunicamycin (0.1 μg ml and 0.25 μg ml). Moreover, expressions of genes involved in the conversion of GABA to succinate was also induced, while genes involved in transport across plasma and mitochondrial membrane showed no response to ER stress. The exogenous treatment of plants with 1-and 5-mM GABA increased plant performance under ER stress but 0.1 mM proved ineffective. Plants treated with GABA under ER stress had decreased expression of ER stress marker genes such as BIP1, BIP3 or CNX, but the expression of genes related to ER stress perception or ER-associated protein degradation showed no changes with respect to GABA treatments.
内质网（ER）是分泌蛋白产生和折叠的主要场所，其在环境胁迫下的内稳态对于维持蛋白质分泌途径至关重要。内质网中未折叠蛋白质的积累和稳态的丧失被称为内质网应激。虽然γ-氨基丁酸（GABA）是植物应激反应的重要调节剂，但它在 ER 应激中的作用尚不清楚。本研究探讨了 GABA 在植物 ER 应激反应中的作用。为此，分析了拟南芥在 ER 应激下 GABA 代谢的变化，然后用外源性 GABA 处理植物以研究 ER 折叠机制对 ER 应激的反应。用抗生素衣霉素处理植物，衣霉素抑制 N-糖基化，从而特异性诱导 ER 应激。这种应激上调了除 GAD2 以外的五个谷氨酸脱羧酶（GAD）基因的表达，并且随着衣霉素浓度的增加（0.1 μg ml 和 0.25 μg ml），拟南芥植物的 GABA 含量增加。此外，参与 GABA 转化为琥珀酸的基因表达也被诱导，而参与跨质膜和线粒体膜运输的基因对 ER 应激没有反应。植物用 1 和 5mM GABA 进行外源处理可以提高 ER 应激下的植物性能，但 0.1mM 则无效。在 ER 应激下用 GABA 处理的植物中，ER 应激标记基因如 BIP1、BIP3 或 CNX 的表达降低，但与 GABA 处理相比，与 ER 应激感知或 ER 相关蛋白降解相关的基因表达没有变化。
