Gibberellic acid modifies the transcript abundance of ABA pathway orthologs and modulates sweet cherry (prunus avium) fruit ripening in early- and mid-season varieties

Abstract

Several phytohormones modulate ripening in non-climacteric fruits, which is triggered by abscisic acid (ABA). Gibberellins (GAs) are present during the onset of ripening in sweet cherry fruits, and exogenous gibberellic acid (GA(3)) application delays ripening, though this effect is variety-dependent. Although an ABA accumulation delay has been reported following GA(3) treatment, the mechanism by which GA modulates this process has not been investigated at the molecular level in sweet cherry. Therefore, the aim of this work is to analyze the effect of GA(3) on the fruit ripening process and the transcript levels of ABA pathway orthologs in two varieties having different maturity time phenotypes. The early-season variety had a rapid transition from yellow to pink fruit color, whereas pink color initiation took longer in the mid-season variety. GA(3) increased the proportion of lighter colored fruits at ripeness in both varieties, but it produced a delay in IAD-a ripening index-only in the mid-season variety. This delay was accompanied by an increased transcript abundance of PavPP2Cs, which are putative negative regulators of the ABA pathway. On the other hand, the early-season variety had increased expression of PavCYP707A2-a putative ABA catabolic gene-, and reduced transcript levels of PavPP2Cs and SnRK2s after the GA(3) treatment. Together these results show that GA modulates fruit ripening, exerting its action in part by interacting with the ABA pathway in sweet cherry.