Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia,
Antonie Van Leeuwenhoek. 2013 Nov;104(5):793-807. doi: 10.1007/s10482-013-9989-y. Epub 2013 Aug 4.
Glutamate decarboxylase (GAD) catalyses decarboxylation of glutamate to gamma-aminobutyrate (GABA) in a metabolic pathway connected to citrate cycle and known as GABA shunt. The gene (gad) was disrupted in Trichoderma atroviride CCM F-534 and viable mutants were characterized. Two of them were found to arise by homologous recombination and were devoid of both GAD activity and GABA. Mutants grew slower as compared to the wild type (F534). In the submerged culture, mutants developed less CO2 and consumed less O2 than the F534 without changing their respiratory quotients. Hyphae of mutants were more ramified than those of F534. Their ramification, in contrast to F534, was not increased by cyclosporin A, a drug causing hyphae ramification of several fungi and which is a calcineurin/cyclophilin inhibitor, or by FK506. Rapamycin, which is a cyclophilin but not calcineurin inhibitor, had a different effect on hyphae ramification in F534 and mutants. To examine the presence of GABA receptors in the fungus the effect of mammalian GABA-receptor modulators, such as bicuculline, gabapentin or carbamazepine on fungal morphology were investigated. Conidia of mutants germinated in a multipolar manner more frequently (up to 80 %) than those of F534. This trait was modified with cyclosporine A, FK506 and GABA receptor modulators in a different manner. Transport of chlorides, an intimate feature of GABA-regulated receptors/channels in animal cells, was measured in vegetative mycelia by means (36)Cl(-) uptake. It was significantly reduced in gad mutants. The results suggest that T. atroviride possesses a signalling pathway that involves GABA, putative GABA receptor(s), calcineurin, target of rapamycin and chloride transporter(s) to regulate physiological functions.
谷氨酸脱羧酶（GAD）在与柠檬酸循环有关的代谢途径中催化谷氨酸脱羧生成γ-氨基丁酸（GABA），该途径称为 GABA 分流。在里氏木霉 CCM F-534 中破坏了该基因（gad），并对存活的突变体进行了特征描述。发现其中两个是通过同源重组产生的，并且缺乏 GAD 活性和 GABA。与野生型（F534）相比，突变体的生长速度较慢。在液体培养中，突变体产生的 CO2 比 F534 少，消耗的 O2 也比 F534 少，但呼吸商没有改变。突变体的菌丝比 F534 的更分枝。与 F534 不同，环孢菌素 A（一种可引起多种真菌菌丝分枝的药物，是钙调神经磷酸酶/亲环素抑制剂）或 FK506 不会增加突变体的分枝。雷帕霉素是一种亲环素但不是钙调神经磷酸酶抑制剂，对 F534 和突变体中的菌丝分枝有不同的影响。为了研究真菌中 GABA 受体的存在，研究了哺乳动物 GABA 受体调节剂（如印防己毒素、加巴喷丁或卡马西平）对真菌形态的影响。与 F534 相比，突变体的分生孢子更频繁地以多极方式发芽（高达 80%）。用环孢菌素 A、FK506 和 GABA 受体调节剂以不同的方式修饰了这种特性。通过（36）Cl-摄取来测量植物性菌丝中的氯离子转运，氯离子转运是动物细胞中 GABA 调节的受体/通道的一个重要特征。在 gad 突变体中，氯离子转运显著减少。结果表明，里氏木霉具有一种信号通路，该通路涉及 GABA、假定的 GABA 受体、钙调神经磷酸酶、雷帕霉素靶蛋白和氯离子转运体，以调节生理功能。
