Expression pattern of ABA metabolic and signalling genes during floral development and fruit set in sweet cherry

Abscisic acid plays a crucial role in the regulation of fruit development and ripening, however, its role in the floral development and the fruit set is still unclear. In the present study, the ABA accumulation and the expression patterns of genes related to ABA metabolism and signalling in sweet cherry were investigated. The results showed that ABA accumulation increased and peaked at stage V in ovary, at stage VI in stamen, and in young fruit it peaked at 7 days after full bloom. The expression pattern of ABA synthetase PaNCED1 was consistent with the changes of ABA accumulation. Among four ABA degradation enzymes PaCYP707As, PaCYP707A4 was highly expressed in ovary, PaCYP707A1 was mainly in stamen, and PaCYP707A2 was in young fruit, and their expressions were reversed to the trend of PaNCED1. With regard to ABA signalling genes, among three ABA receptors PaPYLs, PaPYL2 and PaPYL3 were high expression genes in ovary and in young fruit with similar expression patterns, while PaPYL3 was the high expression gene in stamen. Within six PaPP2Cs, PaPP2C1/2/3 were highly expressed in ovary and young fruit, while PaPP2C3/4 were mainly in stamen. The six PaSnRK2s showed different expression patterns: PaSnRK2.1/2.2/2.4 were highly expressed in ovary and young fruit, while PaSnRK2.1/2.3 were highly expressed in stamen. In situ hybridization results showed that PaPYL3, PaPP2C3 and PaSnRK2.4 were expressed in seed, pulp and fruit peel during fruit set. In conclusion, ABA and its signaling may play an important role in the regulation of floral development and fruit set.