The influence of Cameraria ohridella (Lepidoptera, Gracillariidae) on the activity of the enzymatic antioxidant system of protection of the assimilating organs of Aesculus hippocastanum in an urbogenic environment

Abstract

In the last two decades, the horse chestnut (Aesculus hippocastanum L.), introduced into the steppe zone of Ukraine, has been severely affected by the horse chestnut leaf miner Camereraria ohridella Deschka & Dimič, 1986, which results in damage to the assimilating organs, premature leaf defoliation and, as a consequence, a significant reduction in the reserve substances required for normal life of the plant. In recent studies, the main focus has been placed on the study of the pest’s effects on the non-enzymatic antioxidant protection system of the representatives of the genus Aesculus, while the enzymatic system of horse chestnut protection from the active forms of oxygen under stress is still poorly understood. The purpose of this study was to evaluate the reaction of catalase and two peroxidases of A. hippocastanum leaves, which differ in the level of damage by C. ohridella. The intensity of damage to A. hippocastanum leaves by the horse chestnut leaf miner in the park zones and botanical gardens of Dnipro city was determined, the activity and isoenzyme composition of benzidine-peroxidase, activity of guaiacol-peroxidase and catalase were measured. The lowest average benzidine-peroxidase activity was found in the group of trees with low level of leaf blight and the highest activity – in the group with high level. The opposite dependence was shown by catalase, the activity of which significantly decreases with increasing level of damage inflicted by the phytophage on the chestnut’s assimilating organs. Based on the determination of the variation coefficients, it has been shown that benzidine-peroxidase activity has a higher level of variability than that of catalase and guaiacol-peroxidase. It is established that under the influence of the leaf miner, activity of guaiacol-peroxidase was significantly higher by 87.1% and 75.6%, respectively, for medium and high levels of damage caused to the leaf by this phytophage as compared to that for low levels of damage. The increased level of leaf damage caused by the phytophage is reflected in the change in the isozyme profile of benzidine-peroxidase. The high activity of benzidine-peroxidase in the leaves of A. hippocastanum is due to the presence of several molecular forms that exhibit maximum activity in the narrow pH range (4.15–4.69). Quantitative redistribution of activity between the different molecular forms of benzidine peroxidase can be considered as the main regularity of changes in the expression of benzidine-peroxidase caused by different levels of leaf damage. The results showed that only one benzidine-peroxidase isoform with an isoelectric point of 4.15 shows a significant increase in activity (on average by 2.1 times) in A. hippocastanum leaves with medium and high levels of damage by C. ohridella. Significant reduction in activity is reported for dominant isoperoxidase with an isoelectric point of 4.25 revealing medium pest damage, and for high damage only a decreasing tendency is shown. The data obtained show that horse chestnut trees can specifically respond to mechanical damage by C. ohridella to leaves due to the changes in the activity of individual molecular forms of peroxidase. Further studies of oxidative metabolism are needed to understand the formation of resistance of representatives of the Aesculus genus to damage caused by this moth species based on a wider range of redox enzymes.