The Role of Gamma-Amino Butyric Acid in Short-Term High Temperature Acclimation in Lichen Pseudevernia furfuraceaNihal Gören Sağlam, Fazilet Özlem Albayrak, Dilek Ünal
Objective: Global warming causes many different stresses for plants. High-temperature stress is one of the important problems caused by global warming. Plants develop various tolerance mechanisms to protect themselves against these stresses. γ-Aminobutyric acid (GABA) metabolism has a critical role in various biological processes in plants. GABA plays a critical role in the acclimation to different stress conditions in plants. Lichens can grow in environments exposed to severe abiotic stresses such as drought and extreme heat. The major aim of this study was to identify whether GABA accumulation could improve short-term, high-temperature tolerance in lichen Pseudevernia furfuracea. Materials and Methods: For this aim, P. furfuracea samples were kept in petri dishes in an incubator at 45 ± 2°C for 24 and 48 h. We analyzed the chlorophyll a/b ratio, GABA content, glutamate decarboxylase (GAD) and glutamate dehydrogenase (GDH) activities, which are important enzymes involved in the GABA shunt, and also peroxidase (POD) and catalase (CAT) activities of the antioxidant metabolism. Results: Our study indicated that the chlorophyll a/b ratio was not changed significantly under 45°C within 48 h. POD and CAT activities were significantly decreased in lichen thalli under 45°C, however; GABA accumulation was approximately enhanced by 1.5-fold depending on the time exposure. GAD and GDH activities were significantly increased under high temperature conditions. Conclusions: The acclimilation of P. furfuracea to high temperatures may be related to the increase in GAD and GDH activities. Our findings provided evidence that the GABA shunt could help lichen P. furfuracea to acclimate to high temperatures.