Overexpression of the mitochondrial MT-sHSP23.6 gene during antioxidant activity in tomato cv. Micro-Tom subjected to flooding

Abstract

Plants grown under flooding stress conditions form reactive oxygen species, both during oxygen deficiency and after reoxygenation. The tolerance of plants under these conditions depends on an efficient antioxidant system, which may be influenced by the higher expression of heat shock proteins, such as mitochondrial MT-sHSP23.6. The objective of the present study was to determine whether the overexpression of this gene increases the antioxidant activity in tomato cv. Micro-Tom plants subjected to flooding during the vegetative stage of four fully expanded leaves. The experiment was performed with three genotypes of tomato plants (Solanum lycopersicum Mill. cv. Micro-Tom), one non-transformed denominated “WT” and two modified for high and low expression of the MT-sHSP23.6 gene, subjected to normal irrigation conditions, 72 hours of flooding, and 24 and 192 hours of recovery after the removal of flooding, consisting a 3x4 split-plot factorial design with four replications. Plants were collected at the vegetative stage of 4 fully expanded leaves to determine superoxide dismutase, ascorbate peroxidase and catalase activities, hydrogen peroxide accumulation and lipid peroxidation. Overexpression of the mitochondrial MT-sHSP23.6 gene in the evaluated plants resulted in higher antioxidant system activity. However, it did not necessarily lead to less damage caused by oxidative stress. Low expression of this gene resulted in lower antioxidant system activity and greater damage caused by reactive oxygen species.