RNAseq reveals different transcriptomic responses to GA3 in early and midseason varieties before ripening initiation in sweet cherry fruits

Abstract

Gibberellin (GA) negatively affects color evolution and other ripening-related processes in non-climacteric fruits. The bioactive GA, gibberellic acid (GA3), is commonly applied at the light green-to-straw yellow transition to increase firmness and delay ripening in sweet cherry (Prunus avium L.), though causing different effects depending on the variety. Recently, we reported that GA3 delayed the IAD parameter (a ripening index) in a mid-season variety, whereas GA3 did not delay IAD but reduced it at ripeness in an early-season variety. To further explore this contrasting behavior between varieties, we analyzed the transcriptomic responses to GA3 applied on two sweet cherry varieties with different maturity time phenotypes. At harvest, GA3 produced fruits with less color in both varieties. Similar to our previous report, GA3 delayed fruit color initiation and IAD only in the mid-season variety and reduced IAD at harvest only in the early-season variety. RNA-seq analysis of control- and GA3-treated fruits revealed that ripening-related categories were overrepresented in the early-season variety, including ‘photosynthesis’ and ‘auxin response’. GA3 also changed the expression of carotenoid and abscisic acid (ABA) biosynthetic genes in this variety. In contrast, overrepresented categories in the mid-season variety were mainly related to metabolic processes. In this variety, some PP2Cs putative genes were positively regulated by GA3, which are negative regulators of ABA responses, and MYB44-like genes (putative repressors of PP2Cs expression) were downregulated. These results show that GA3 differentially modulates the transcriptome at the onset of ripening in a variety-dependent manner and suggest that GA3 impairs ripening through the modification of ripening associated gene expression only in the early-season variety; whereas in the mid-season variety, control of the ripening timing may occur through the PP2C gene expression regulation. This work contributes to the understanding of the role of GA in non-climacteric fruit ripening.

Could Causal Discovery in Proteogenomics Assist in Understanding Gene–Protein Relations? A Perennial Fruit Tree Case Study Using Sweet Cherry as a Model

“…Based on the literature [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], these observed direct cause-effect relations can be justified. For instance, the Ca 2+ signaling category of ME20 (PaCDPK7; Pav_sc0001218.1_g200.1.mk) and ME27 (PaCDPK5; Pav_sc0002962.1_g130.1.mk, PaCDPK1; Pav_sc0000869.1_g430.1.mk, PaCAMTA2; Pav_sc0000334.1_g570.1.mk) may be linked to the synthesis of phenylpropanoids, notably anthocyanins during fruit ripening (ME30, PaAGT5; Pav_sc0000348.1_g1140.1.mk) [ 26 ].…”

“…In addition, caffeoyl shikimate esterase of ME27 (PaCSE; Pav_sc0000130.1_g1060.1.mk), which is included in phenylpropanoid biosynthesis, participates in the process of the endocarp lignification in stone fruits [ 27 ]. Moreover, leucoanthocyanidin reductase of ME20 (PaLAR; Pav_sc0003685.1_g130.1.mk) has been found to increase when gibberellic acid (GA 3 ) was exogenously applied in sweet cherries during fruit development [ 28 ]. This protein was associated with delayed fruit coloring due to inhibition of anthocyanin biosynthesis in sweet cherry [ 28 ] and apple [ 29 ] fruit.…”

“…Moreover, leucoanthocyanidin reductase of ME20 (PaLAR; Pav_sc0003685.1_g130.1.mk) has been found to increase when gibberellic acid (GA 3 ) was exogenously applied in sweet cherries during fruit development [ 28 ]. This protein was associated with delayed fruit coloring due to inhibition of anthocyanin biosynthesis in sweet cherry [ 28 ] and apple [ 29 ] fruit.…”

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].…”