PpMAPK6 regulates peach bud endodormancy release through interactions with PpDAM6

The MADS-box(DAM)gene PpDAM6,which is related to dormancy,plays a key role in bud endodormancy release,and the expression of PpDAM6 decreases during endodormancy release.However,the interaction network that governs its regulation of the endodormancy release of flower buds in peach remains unclear.In this study,we used yeast two-hybrid(Y2H)assays to identify a mitogen-activated protein kinase,PpMAPK6,that interacts with PpDAM6 in a peach dormancy-associated SSHcDNA library.PpMAPK6 is primarily located in the nucleus,and Y2H and bimolecular fluorescence complementation(BiFC)assays verified that PpMAPK6 interacts with PpDAM6 by binding to the MADS-box domain of PpDAM6.Quantitative real-time PCR(qRT-PCR)analysis showed that the expression of PpMAPK6 was opposite that of PpDAM6 in the endodormancy release of three cultivars with different chilling requirements(Prunus persica‘Chunjie’,Prunus persica var.nectarina‘Zhongyou 5’,Prunus persica‘Qingzhou peach’).In addition,abscisic acid(ABA)inhibited the expression of PpMAPK6 and promoted the expression of PpDAM6 in flower buds.The results indicated that PpMAPK6 might phosphorylate PpDAM6 to accelerate its degradation by interacting with PpDAM6.The expression of PpMAPK6 increased with decreasing ABA content during endodormancy release in peach flower buds,which in turn decreased the expression of PpDAM6 and promoted endodormancy release.

Accumulated chilling hours during endodormancy impact blooming and fruit shape development in peach(Prunus persica L.)

Winter chill is essential for the growth and development of deciduous species. To understand the relationship between accumulated chilling hours during endodormancy and blooming and fruit shape development, we controlled chilling hours and investigated their effects on blooming date and fruit shape of peaches. The results showed that the number of days to full bloom date and the heat requirement for blooming were negatively correlated with accumulated chilling hours. Accumulated chilling hours were significantly negatively correlated with fruit shape index and fruit tip lengths, suggesting that the number of chilling hours affect the fruit shape development. Fewer accumulated chilling hours may be the major reason for longer fruit shape and protruding fruit tips. In conclusion, our results indicate specifically that decreased winter chilling hours can delay the bloom date and may lead to aberrant fruit shape development in peaches. Our study provides preliminary insights into the response of temperate fruit species to global climate change.

Relation Between Endodormancy Induction and Changes in Two Main Electron Transport Pathways of Nectarine Buds

Operation regulations of two main electron transport pathways in nectarine （Prunus persica var. nectariana cv. Shuguang） buds during endodormancy induction were studied to understand possible roles which two main electron transport pathways played in the buds of deciduous fruit trees during endodormancy induction. Respiratory inhibitors （KCN and SHAM） were used to investigate total respiration rate （Vt）, the development and operation of the alternative pathway and partitioning of electrons between the cytochrome and alternative pathways in nectarine buds during endodormancy induction. Results indicated that changes of Vt in flower and leaf buds showed single and double hump-shaped curves, respectively. In endodormancy induction, the capacity （Valt,） and activity （ρValt） of the alternative pathway rapidly increased, but changes of them had different patterns during the entire measuration. At the same time, changes of engagements of the alternative （ρValt/Vt） and cytochrome pathway （ρ′Vcyt/Vt） were opposite, and ρ′Vcyt/Vt was always further higher than ρValt/Vt during the entire measuration. All these results indicated that the development and operation of the alternative pathway played important roles in endodormancy induction, but the cytochrome pathway was the main pathway for mitochondrial electron transport in buds during endodormancy induction.

Insights into Seasonal Dormancy of Perennial Herbaceous Forages

Seasonal dormancy is an adaptive mechanism where plants suspend growth and become physiologically inactive to avoid extreme environmental conditions. Environmental factors like temperature, photoperiod, nutrients, and soil moisture control plant growth and development through various complex molecular mechanisms. Crown and seed dormancy of plants are mostly influenced by day length and temperature. Genes and physiological pathways triggered by these two factors along with genotype variability are some targets to manipulate seasonal dormancy. There is genetic variation in the depth and duration of seasonal dormancy. Therefore, their genetic manipulation is possible. Manipulations of summer and fall dormancy are relatively easier compared to winter dormancy because plants require protection of their apical meristem from freezing temperatures and limited water supply. Genetic factors that regulate seed dormancy may also have regulatory role for seasonal dormancy of the maternal plants. Limited genetic and genomic information are available for seasonal dormancy in herbaceous perennial species. Knowledge of genes controlling seasonal dormancy of eudicots, forest trees, and horticultural crops could be interpolated to explore possible dormancy mechanisms in perennial forages. This study reviews current knowledge of seasonal dormancy of herbaceous forages emphasizing the genetic and physiological context that would be valuable to breeders and plant biologists to expand the production season of perennial species by developing non-dormant and semi-dormant cultivars.