Abstract
In recent decades, atmospheric pollution led to a progressive reduction of the ozone layer with a consequent increase in UV-B radiation. Despite the high adaptation of olive trees to the Mediterranean environment, the progressive increase of UV-B radiation is a risk factor for olive tree cultivation. It is therefore necessary to understand how high levels of UV-B radiation affect olive plants and to identify olive varieties which are better adapted. In this study we analyzed two Italian olive varieties subjected to chronic UV-B stress. We focused on the effects of UV-B radiation on RubisCO, in terms of quantity, enzymatic activity and isoform composition. In addition, we also analyzed changes in the activity of antioxidant enzymes (SOD, CAT, GPox) to get a comprehensive picture of the antioxidant system. We also evaluated the effects of UV-B on the enzyme sucrose synthase. The overall damage at biochemical level was also assessed by analyzing changes in Hsp70, a protein triggered under stress conditions. The results of this work indicate that the varieties (Giarraffa and Olivastra Seggianese) differ significantly in the use of specific antioxidant defense systems, as well as in the activity and isoform composition of RubisCO. Combined with a different use of sucrose synthase, the overall picture shows that Giarraffa optimized the use of GPox and opted for a targeted choice of RubisCO isoforms, in addition to managing the content of sucrose synthase, thereby saving energy during critical stress points.
Highlights
The olive tree (Olea europaea L.) is one of the most important and oldest crops in the Mediterranean basin
Each spot is indicated in percentage relative to each individual analysis time. In this manuscript we have analyzed the effects of UV-B radiation on the enzymatic activity and isoform composition of RubisCO, together with the effects of UV-B on the enzyme-based antioxidant system and on the activity of sucrose synthase, one of the key enzymes in sucrose metabolism
As a general stress parameter, we analyzed the differential accumulation of heat shock protein 70 kilodaltons (Hsp70), one of the most abundant families of chaperonins involved in stress response [37]
Summary
The olive tree (Olea europaea L.) is one of the most important and oldest crops in the Mediterranean basin. Despite the high adaption of olive trees to the environmental conditions of the Mediterranean region, the progressive increasing levels of UV-B radiation (e.g., [4,5]), together with additional environmental factors, such as sky cloudiness and high air pollutants, are a risk to olive cultivation and productivity [6,7,8]. It is necessary to understand how high levels of UV-B radiation affect olive plants and to identify olive varieties better adapted to these conditions. This will allow farmers to grow selected varieties that are suitable for the current and future environmental scenarios
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