Changes in the distribution of cell wall hemicelluloses during fruit abscission in olive

Although cell-wall modification is believed to underlie the changes in organ abscission, information concerning the changes in cell-wall hemicellulose polysaccharides is still limited. The aim of this research was to analyse the spatio-temporal patterns of the distribution of different hemicelluloses in the abscission zone (AZ) during natural ripe-fruit abscission in olive (Olea europaea L.). We employed immunogold labelling in ripe fruit during olive AZ cell separation, using an expanded set of monoclonal antibodies that recognize different types of hemicelluloses (LM11, LM15 and LM21) epitopes, and transmission electron microscopy imaging. Our data demonstrate that AZ cell separation was accompanied by a reduction in the detection of the LM15 xyloglucan epitopes in AZ cell walls, whereas AZ cells were found to be enriched with respect to the xylan levels of the cell wall during olive ripe fruit abscission. By contrast, AZ cell wall polysaccharide remodeling did not involve mannans. Taken together, the results indicate that AZ cell wall dynamics during olive ripe fruit abscission involves hemicellulose modifications. This is the first study available demonstrating temporal degradation of hemicelluloses in the AZ at the subcellular level.