UV-B pre-irradiation induces cold tolerance in tomato fruit by SlUVR8-mediated upregulation of superoxide dismutase and catalase

Abstract

The impact of ultraviolet-B (UV-B) treatment on oxidative stress, cold damage, and antioxidant enzymes and the role of the UV-B photoreceptor SlUVR8 in tomatoes during cold storage were investigated. Mature-green tomato fruit were irradiated with 1, 10, or 100 μmol m−2 s-1 UV-B for 1, 3, or 6 h respectively before cold-storage. The chilling injury index (CI), H2O2, O2−, ion leakage, and malondialdehyde (MDA) content in tomatoes stored at 2 ℃ increased during storage, while irradiation with 10 μmol m−2 s-1 UV-B for 3 h before storage significantly reduced H2O2 and O2−, membrane damage and chilling injury. Expression of CuZuSOD, FeSOD and CAT1 and the activities of their encoded enzymes superoxide dismutase (SOD) and catalase (CAT) were markedly raised in UV-B-pre-irradiated tomatoes and correlated significantly with the reductions in H2O2, O2−, ion leakage, MDA, and CI, which suggested that UV-B pre-irradiation might exert its effects by activating the antioxidant enzymes. Silencing SlUVR8 dramatically counteracted the UV-B-mediated effects on enzyme expression while the contents of H2O2, O2−, ion leakage, MDA, together with the CI in SlUVR8-silenced tomatoes were significantly higher. The data showed that silencing of SlUVR8 not only suppressed UV-B-activated SOD and CAT expression, but also prevented UV-B-alleviated oxidative stress and chilling injury. The findings indicated that SlUVR8 was required for UV-B-induced cold tolerance in tomato fruit and demonstrated that UV-B irradiation before cold storage activated SOD and CAT in an SlUVR8-dependent manner.