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 (GA3) application delays ripening, though this effect is variety-dependent. Although an ABA accumulation delay has been reported following GA3 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 GA3 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. GA3 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 GA3 treatment. Together these results show that GA modulates fruit ripening, exerting its action in part by interacting with the ABA pathway in sweet cherry.

Canopy Spraying of Abscisic Acid to Improve Fruit Quality of Different Sweet Cherry Cultivars

“…Previously the role of ABA on sweet cherry fruit maturity has usually been studied in early-maturing cultivars (Satonishiki, Hongdeng, Prime Giant) 13,16,23 , with only a few experiments in other mid-maturing cultivars such as 'Bing' 19 and 'Lapins' 17 . Regardless of this, the exogenous application is not a common agronomic practice in sweet cherry in comparison to other growth regulators such as gibberellin (GA3) 18,[24][25][26][27][28][29][30] . Furthermore, the genotypic effect on the ABA response has not been fully addressed.…”

“…others have reported that GA3 treatment 17,18,29 and fluridone treatment increase the size of sweet cherry fruits 29 . A summary of the effects of the different ABA treatments in cultivars per season is shown in Table 1.…”

“…The difference in the consistent decrease in fruit size (width and weight) in ABA canopy sprayed 'Lapins' sweet cherry fruits at harvest, versus the seasonal variations associated with the 'Glenred' cultivar, may be associated with the differential response that early-and mid-maturing cultivars have to additional phytohormones such as gibberellic acid. Recently we have reported the GA3 modifies the transcript abundance of ABA pathway orthologs and modulates sweet cherry fruit ripening in early-and mid-maturing cultivars 18 and that there is a differential transcriptional response between these cultivars treated with GA3 30 .…”

Canopy Spraying of Abscisic Acid to Improve Fruit Quality of Different Sweet Cherry Cultivars

“…Previously the role of ABA on sweet cherry fruit maturity has usually been studied in early-maturing cultivars ('Satonishiki', 'Hongdeng', 'Prime Giant') [11,14,21], with only a few experiments in other mid-maturing cultivars such as 'Bing' [17] and 'Lapins' [15]. Regardless of this, the exogenous application is not a common agronomic practice in sweet cherry in comparison to other growth regulators such as gibberellin (GA 3 ) [16,[22][23][24][25][26][27][28]. Furthermore, the genotypic effect on the ABA response has not been fully addressed.…”

“…The difference in the consistent decrease in fruit size (width and weight) in ABA canopy sprayed 'Lapins' sweet cherry fruits at harvest, versus the seasonal variations associated with the 'Glenred' cultivar, may be associated with the differential response that early-and mid-maturing cultivars have to additional phytohormones such as gibberellic acid. Recently we have reported the GA 3 modifies the transcript abundance of ABA pathway orthologs and modulates sweet cherry fruit ripening in early-and mid-maturing cultivars [16] and that there is a differential transcriptional response between these cultivars treated with GA 3 [28].…”