Olive Varieties under UV-B Stress Show Distinct Responses in Terms of Antioxidant Machinery and Isoform/Activity of RubisCO

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.

Chemical Profiling of Two Italian Olea europaea (L.) Varieties Subjected to UV-B Stress

“…This suggested that the UV-B stress response was weaker in Olivastra Seggianese, and it is possible this variety was unable to engage the same defense mechanisms as Giarraffa, based on readjustments of the levels of the fatty acids. These results aligned with our previous work, in which lipid peroxidation was only noticeable in the Olivastra Seggianese variety (particularly from T2 to T8) [ 24 ]. The absence of variations in lipid peroxidation [ 24 ] in stressed Giarraffa plants could be related to the higher palmitic, α-linolenic, and stearic acid contents found in these plants.…”

“…These results aligned with our previous work, in which lipid peroxidation was only noticeable in the Olivastra Seggianese variety (particularly from T2 to T8) [ 24 ]. The absence of variations in lipid peroxidation [ 24 ] in stressed Giarraffa plants could be related to the higher palmitic, α-linolenic, and stearic acid contents found in these plants. Indeed, fatty acids have been described as constitutive elements of complex lipids, but several studies also suggested their direct involvement in abiotic and biotic responses to stress in plants [ 39 , 40 ].…”

“…These studies unraveled adjustments in important phenolic compounds (e.g., secoiridoids, flavonoids, and hydroxycinnamic acid derivatives), carbohydrates, and lipophilic metabolites related to cuticle wax (e.g., long-chain alkanes and terpenes), and identified some metabolites related to ROS scavenger action (e.g., thymol glycosides) and maintenance of membrane integrity (e.g., fatty acids and steroids) [ 9 , 16 , 17 , 22 ]. In previous works [ 23 , 24 ], we analyzed the physiological and biochemical responses of two economically important Italian olive varieties to UV-B stress. In the present study, the integration of metabolomics with these previous data allowed a deeper understanding of metabolite dynamics and their connection in a more extensive network of pathways involved in stress response.…”

Distinct Tomato Cultivars Are Characterized by a Differential Pattern of Biochemical Responses to Drought Stress

“…It is assumed that upon stress modifications can generate RubisCO isoforms that are better suited to cope with a demanding situation. In support of this hypothesis, similar work on olive leaves subjected to UV-B stress [84] and a paper on Micro-Tom leaves subjected to heat stress [85] can be cited. In both cases, the stress treatment altered the profile of RuBisCO isoforms resulting in a more targeted use of isoforms, those most capable of functioning in the altered environmental conditions.…”

“…This antibody was purified from human HeLa cells. It recognizes protein homologues in plants and its efficiency has been confirmed in Citrus L. and pepper plants [106] as well as in leaves of olive trees [84].…”