ABA influences color initiation timing in P. avium L. fruits by sequentially modulating the transcript levels of ABA and anthocyanin-related genes

Abstract

In sweet cherry, as in most non-climacteric species, abscisic acid (ABA) plays a major role in the control of fruit ripening and color development. Although the ABA treatment of sweet cherry fruits has been reported to upregulate anthocyanin pathwayrelated genes or ABA pathway-related genes, the temporality of molecular and physiological events occurring during color development and the ABA control of these events during the color initiation are lacking in this species. In this work, we analyzed variations in the Index of Absorbance Difference (IAD), a maturity index, and total anthocyanins along with changes in transcript abundance of ABA and anthocyanin pathway-related genes, from light green to red fruit stages. PavNCED1 and ABA signaling pathway-related genes upregulated when fruits transitioned from light green to pink stage, whereas anthocyanin pathway-related transcripts increased from pink to the red stage, together with increases in the anthocyanin content and IAD, suggesting sequentiality in molecular and physiological events during color development. Additionally, ABA applied at color initiation in planta advanced IAD, increased anthocyanin content, and yielded darker fruits at harvest. These changes were accompanied by changes in the transcript accumulation of ABA and anthocyanin pathway-related genes. This in planta treatment of sweet cherry fruits with ABA confirms that ABA is a central player in the control of color initiation in sweet cherries, associated with the transcript accumulation of genes involved in ABA homeostasis and signaling, which is followed by the up-regulation of anthocyanin pathway-related genes and color development.

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

“…It is well known that ABA increases color due to an increase in the accumulation of anthocyanins in sweet cherry 13,15,16 and in other non-climacteric fruits such as grapes 10 and strawberry 9,12 . We have also seen fruit color changes in the 'Lapins' cultivar when the tree canopy was sprayed with ABA 17 , and similar results were found in the seasons that we report in this paper. However, here we have also compared this response in 'Lapins' with other cultivars during the same season.…”

“…The exogenous application of ABA in sweet cherry fruits had been studied nearly 30 years ago 13 . 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] .…”

“…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.…”

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

“…In the mid-maturing sweet cherry variety Lapins, we previously found that GA 3 increases PavPP2C3 and PavPP2C4 transcripts and delays the increase in the ripening index, IAD 17 , supporting the present findings. Contrary to GA 3 , we recently showed that ABA treatment advances the IAD increase related to PavNCED1 transcript abundance accumulation and ABA content increase 45 . These results suggest a switch for the control of ripening timing where ABA advances and GA 3 delays the ripening initiation in sweet cherry fruits.…”

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

“…The exogenous application of ABA in sweet cherry fruits had been studied nearly 30 years ago [11]. 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].…”