On the role of physiological substances, abscisic acid and its biosynthetic genes in seed maturation and dormancy of tree peony (Paeonia ostii ‘Feng Dan’)

Abstract The seeds of tree peony have a strict dormancy characteristic, which seriously affects seed germination rate and seedling emergence uniformity. Abscisic acid (ABA) is one of the most important plant hormones regulating seed maturation and dormancy. In this study, the seeds of tree peony ( Paeonia ostii ‘Feng Dan’) were collected at different days after pollination (DAP), and the morphological, physiological and hormonal changes as well as five ABA biosynthetic genes expression were determined in seeds. The results indicate that the soluble sugar, starch and soluble protein contents as well as rooting rate were increased to different degrees; whereas, ABA content increased in the early and middle stages and then decreased later. At transcriptional levels, PoNCED1 and PoZEP1 probably together have a rate-limiting function in ABA biosynthesis with a division of roles, and PoSDR1 may induce substantial ABA biosynthesis in the middle and late development stages; furthermore, PoCHY1 should have multiple functions and PoAAO1 acts as a drought induced gene. This is the first report of ABA biosynthesis in the seeds of tree peony, and it will enable the role of ABA in seed dormancy and germination to be better understood. Furthermore, it may offer help by enhancing tree peony breeding efficiency.