RhERF1 and RhERF4 involved in ethylene and auxin-regulated petal abscission by influencing pectin degradation. Rosa hybrid cultivar cultivar:Samantha

The timing of organ abscission is regulated by the balance of two hormones, ethylene and auxin. The execution of organ shedding is due to loss of middle lamella pectin in abscission zone (AZ). However, it is unclear what mechanisms sense the balance of auxin and ethylene to regulate degradation of pectin during abscission. In the study reported here, we identified two ethylene response factors in rose (Rosa hybrid), RhERF1 and RhERF4, play roles in petal abscission. The expression of RhERF1 and RhERF4 is regulated by ethylene and auxin, respectively. Silencing of RhERF1 and RhERF4 accelerates petal abscission, and reduces pectin contents in rose petal AZ. Global expression analysis and RT-PCR assay revealed that RhERF1 and RhERF4 regulate the genes encoding pectin metabolizing enzymes. RhERF1 and RhERF4 are shown to bind to the promoter of β-galactosidase 1 (RhBGLA1) gene. Silencing of RhBGLA1 delays petal abscission in rose. These results show that during petal abscission, RhERF1 and RhERF4 integrate and coordinate ethylene and auxin signals to modulate pectin metabolism in part by regulating RhBGLA1 expression.