Investigation of interaction between alpha lipoic acidsignalization and antioxidant mechanism under osmotic stressconditions

In the current study, it has been aimed to determine the interactions between alpha lipoic acid (ALA) signaling and reactive oxygen species (ROS) and antioxidant compounds in maize seedlings exposed to osmotic stress. In the seedlings exposed to the stress, ALA treatment was found to increase the endogenous ALA content, glutathione (GSH) and ascorbate (ASC) amounts and antioxidant enzyme activities and the expression levels of some genes coding the enzymes, while decreasing the ROS level. Also, it was observed that ALA content decreased when ROS, GSH and ASC levels were decreased by oxygen radical scavenger DMTU, GSH biyosynthesis inhibitör BSO and ASC biyosynthesis inhibitör AF, respectively. However, GSH and ASC amounts, activities of superoxide dismutase (SOD), catalase (CAT) and ASC-GSH cycle enzymes increased but ROS level decreased when endogenous ALA content enhanced by exogenous ALA treatment in radical scavenger or inhibitör applied seedings. Changes in enzyme activities were found to be compatible with findings of SOD and ASCORBATE PEROXIDASE1 gene expression. It was determined that ALA decreased the CAT1 gene expression level when ROS and GSH were reduced by inhibitors. In the light of the findings, it was concluded that ALA can stimulate the antioxidant system by ROS signaling or by interacting with antioxidant compounds such as GSH and ASC and thus it may be involved in the ASC-GSH cycle.