Petal abscission in roses is associated with the activation of a truncated version of the animal PDCD4 homologue, RbPCD1

Abstract

Abscission is a developmental process that leads to shedding of organs not needed by the plant. Apart from wallhydrolysis, the cells of the abscission zone (AZ) are also believed to undergo programmed cell death (PCD). Weshow that ethylene-induced petal abscission inRosa bourbonianais accompanied with the activation ofRbPCD1(PROGRAMMED CELL DEATH LIKE 1) encoding a protein of 78 amino acids. Its expression increases duringnatural and ethylene-induced petal abscission. Its transcription in most tissues is up-regulated by ethylene.RbPCD1 shows similarity to the N-terminal domain of animal PDCD4 (PROGRAMMED CELL DEATH PROTEIN 4)proteins that are activated during apoptosis and function as transcriptional and translational repressors. RbPCD1resides in the nucleus and cytoplasm and acts as a transcriptional repressor. Constitutive expression ofRbPCD1intransgenic Arabidopsis is seedling lethal. Heat-induced expression ofRbPCD1under the soybean heat-shockpromoter affects leaf function, inflorescence development, silique formation, seed yield and reduces survival.Nuclear localization of RbPCD1 is necessary for manifestation of its effects. RbPCD1 may be necessary to mediatesome of the ethylene-induced changes during abscission and senescence in specific tissues.