Dynamic of carbohydrate metabolism and the related genes highlights PPP pathway activation during chilling induced bud dormancy release in tree peony (Paeonia suffruticosa)

Tree peony is a well-known ornamental plant, and its dormancy is a biological characteristic and a necessary process before bud sprouting and flowering. Carbohydrate metabolism plays an important role in regulating many physiological processes of plants. With the extension of chilling treatment, morphology changes indicated that the percentages of sprouting and blossom increased, and nearly 100 percentages of the apical buds sprouted and then blossomed after 21 d 0-4 °C artificial chilling duration. Sufficient chilling fulfillment significantly increased the total respiration rate. Ten putative respiratory metabolism and starch degradation-related genes including PsAMY, PsBMY, PsHK, PsPFK, PsPK, PsPDH, PsIDH, PsOGDH, Ps6PGDH and PsG6PDH were isolated, and the qPCR results indicated that chilling duration induced their expressions and most of them reached the maximum value after 21 d chilling exposure. The activities of the three key enzymes of EMP, TCA and PPP pathway, HK, IDH and G6PDH, were consistent with the expression levels of the corresponding genes (PsHK, PsIDH and PsG6PDH). Although the related genes of EMP were up-regulated and the activities of key enzymes increased, but the contribution of EMP gradually decreased during dormancy release in tree peony, and the increasing contribution of PPP pathway was higher than that of TCA pathway. Our results suggested that the activation of PPP pathway might play an important role in chilling-induced dormancy release of tree peony.