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UV-C radiation modifies the ripening and accumulation of ethylene response factor (ERF) transcripts in tomato fruit

Severo, Joseana, Tiecher, Aline, Pirrello, Jullien, Regad, Farid, Latché, Alain, Pech, Jean-Claude, Bouzayen, Mondher, Rombaldi, Cesar Valmor
Postharvest biology and technology 2015 v.102 pp. 9-16
1-methylcyclopropene, aminocyclopropanecarboxylate oxidase, beta-carotene, biochemical pathways, chlorogenic acid, delta-tocopherol, ethylene, ethylene production, gene expression, lycopene, postharvest treatment, putrescine, quercetin, relative humidity, ripening, shelf life, spermidine, tomatoes, transcriptome, ultraviolet radiation
Ultraviolet-C (UV-C) radiation is used as a postharvest treatment to prolong the shelf life of fruit. However, this stressful process may also affect ethylene production and, consequently, the expression of genes encoding ethylene response factors (ERFs). To test this hypothesis, MicroTom tomatoes harvested at the breaker stage were subjected to: 1 – application of 3.7kJm−2 UV-C radiation, 2 – application of 2μLL−1 1-methylcyclopropene (1-MCP) followed by UV-C radiation; and 3 – without 1-MCP or UV-C (control treatment). After treatment all fruit were stored for 12d at 21±2°C and 80±5% relative humidity (RH). Although UV-C radiation increased ACC oxidase transcripts and stimulated ethylene production, the ripening evolution was delayed. Fruit treated with UV-C showed lower accumulation of lycopene, β-carotene, lutein+zeaxanthin and δ-tocopherol; but retained higher levels of chlorogenic acid, ρ-coumaric acid and quercetin after 6d. Additionally, UV-C treated fruit had higher contents of polyamines (putrescine and spermidine). Among the 14 ERFs studied, 11 (Sl-ERF A.1, Sl-ERF A.3, Sl-ERF B.1, Sl-ERF B.2, Sl-ERF B.3, Sl-ERF C.6, Sl-ERF D.1, Sl-ERF D.3, Sl-ERF E.1, Sl-ERF F.5, Sl-ERF G.2) exhibited increased transcript accumulation, 2 ERFs (Sl-ERF E.2 and Sl-ERF E.4) showed decreased transcript accumulation and only 1 ERF (Sl-ERF E.3) was not significantly affected by UV-C treatment. As expected, the transcript profiles of 1-MCP and/or UV-C-treated tomatoes demonstrate that ethylene plays an important role in the expression of ERFs. The delay in fruit ripening may be caused by the activation of ERFs that could act as regulators of metabolic pathways during ripening. However, this hypothesis needs to be better tested. In conclusion, a relationship has been established between UV-C treatment and ripening delay, correlated to changes in 13 ERF transcripts evaluated during postharvest treatment.