Grafting is an effective technique for increasing the resistance of vegetables to biotic and abiotic stresses. It has been widely applied to produce solanaceous and melon vegetables. Temperature is an important external factor affecting graft formation. However, the molecular mechanism by which external ambient temperature affects tomato graft formation remains unclear. In this study, we demonstrated that elevating ambient temperature during grafting to 35 °C for more than 24 h after grafting accelerated vascular reconnection. We generated self- or heterografted combinations between phyB1B2 and pif4 loss-of-function mutant and wild-type plants, and were mutants unresponsive to graft formation at elevated ambient temperature. In addition, elevated ambient temperature induced SlPIF4 expression during grafting. SlPIF4 directly binds the promoters of auxin biosynthesis genes SlYUCCA s and activates their expression. Further investigation revealed auxin accumulation in the graft junction under elevated ambient temperature. The results illuminate the mechanism by which the PHYB-PIF4-auxin module promotes tomato graft formation in response to elevated ambient temperature.
Liu Yitong,Liu Shuangrong,Jing Yanjun,Li Jialong,Lin Rongcheng
Seed dormancy enables plants to delay germination until conditions are favorable for the survival of the next generation. Seed dormancy and germination are controlled by a combination of external and internal signals, in which light and ethylene act as critical regulators. However, how light and ethylene are interlinked to control these two processes remains to be investigated. Here, we show that ethylene and its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), promote seed germination under light. Light facilitates the conversion of ACC to ethylene, in which phytochrome B (phyB) and FAR-RED ELONGATED HYPOCOTYL3 (FHY3) are functionally required. ACC oxidases (ACOs) catalyze the conversion of ACC to ethylene, among which ACO1 is specifically and predominantly expressed in imbibed seeds. Ethylene induces FHY3 protein accumulation in imbibed seeds, whereby FHY3 directly binds to ACO1 promoter and specifically mediates light-promoted ACO1 expression. Light promotes ACO1 protein accumulation. Overexpression of ACO1 significantly promotes seed germination, and almost completely restores the dormant defect of fhy3 loss-of-function mutants. In summary, this study reveals an ethylene-responsive regulatory cascade of phyB-FHY3-ACO1 that integrates external light input with internal factors to regulate seed dormancy and germination.
危险品化学品经营许可证（带存储）