Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 138

Cell separation that occurs during fleshy fruit abscission and dry fruit dehiscence facilitates seed dispersal, the final stage of plant reproductive development. The polygalacturonase (PG) multigene family encodes enzymes involved in the depolymerization of pectin homogalacturonan within the primary cell wall and middle lamella. PG activity is commonly found in the separation layers during organ abscission and dehiscence. Roongsattham et al. (2012) identified the PGs responsible for the high activity previously observed in the abscission zone (AZ) during fruit shedding of the oil palm, and they analysed PG gene expression during oil palm fruit ripening and abscission. The authors identified 14 transcripts that encode PGs, all of which are expressed in the base of the oil palm fruit. The accumulation of five PG transcripts increase, four transcripts decrease and five do not change during ethylene treatments that induce cell separation. One PG transcript (EgPG4) is the most highly induced in the fruit base, with a 700- to 5000-fold increase during ethylene treatment. In situ hybridization experiments indicate that the EgPG4 transcript increases preferentially in the AZ cell layers in the base of the fruit in response to ethylene prior to cell separation. The expression pattern of EgPG4 is consistent with the temporal and spatial requirements for cell separation to occur during oil palm fruit shedding.