Glutathione S-Transferase activities and glutathione levels in needles of drought stressed Pinus brutia Ten. trees

Abstract

Aim: Glutathione S-transferases (GST) take roles under stress conditions by the conjugation of Glutathione (GSH) to electrophilic substrates to increase their solubility and facilitating further metabolic processing. This is one of the main pathways functioning in stress resistance and, for dought stress, there is not yet a study on Pinus brutia Ten. which is a very important forest tree of Turkey. Materials and Methods: The needles of 30 different individuals of Pinus brutia Ten. were collected three times in the season: at the begining, in the middle and at the end of summer (June-August). The total precipitation and the temperature of the region were surveyed during sampling period. The osmotic pressure values, total GST activities and the GSH pools of the needle samples were measured and statistically analysed. Results: The osmotic pressure values showed 16% increase throughout the season. Moreover, total precipitation and temperature values demonstrated that the highest drought stress was observed at the end of sampling period. Approximately 80% of increase in total GST activity between the beginning and the end of summer probably indicated the response against drought; although there was no significant change in the GSH pool. Conclusion: The presence of drought, elevated osmotic pressure and a satistically significant (p<0.005) increase in total GST activities in needle samples were detected. The lack of direct correlation between the GSH pool and total GST activities was explained by the rate of GSH biosynthesis and its redox cycling.