Abstract
Plant organ abscission is a complex developmental process that involves cell separation regulated by the environment, stress, pathogens and the physiological status of the plant. In particular, seed and fruit abscission play a central role in seed dispersion and plant reproductive success, and are common domestication traits with important agronomic consequences for many crop species. Oil palm (Elaeis guineensis) is cultivated throughout the tropical regions as one of the most economically important oil crop species in the world. The unsynchronized ripening of the oil palm fruit bunch leads to the abscission of the ripest fruit and consequently high labor cost for harvest and loss of yield. In this context, the control of oil palm ripe fruit abscission is an important agricultural concern for the cultivation of oil palm in a sustainable and cost effective way. In the present study, a protocol to phenotype the oil palm fruit abscission process was developed and used to identify a tree in the field that does not undergo ripe fruit abscission. In parallel, transcriptome and proteome analyses of the oil palm ripe fruit abscission zone (AZ) during abscission induced experimentally by ethylene compared to the AZ undergoing natural abscission in the field was performed. A total of 1,957 candidate genes were identified statistically as differentially expressed in the ripe fruit AZ during ethylene-induced abscission. Furthermore, a total of 64 of these differentially abundant candidates were statistically specific or enriched at least during one time point of the ethylene induced abscission, compared to their profiles in the AZ of immature fruit and the pedicel of ripe fruit, where cell separation is not observed. The profiles of these gene candidates were examined in the ripe fruit AZ undergoing natural abscission in the field to validate their potential role during abscission. Finally, the profiles of selected candidate genes were then examined in the AZ of the tree observed not to undergo fruit abscission in the field. The combined approaches provide evidence of wide scale conservation of the molecular components involved in organ abscission of this monocot compared with the model dicot plants tomato and Arabidopsis. For example, the identification of polygalacturonases very similar to those that function during Arabidopsis floral organ abscission suggests a conservation of the components for pectin disassembly despite the phylogenetic distance between these species. In addition, the data from the global analysis and complementary molecular, cellular and biochemical approaches suggest novel components and provide a robust list of genes and processes important for AZ function during ripe fruit abscission of this important monocot crop species.