Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2002
Publication Date: 11/1/2002
Citation: RUPERTI, B., BONGHI, C., ZILIOTTO, F., PAGNI, S., RASORI, A., VAROTTO, S., TUNUTTI, P., GIOVANNONI, J.J., RAMINA, A. CHARACTERIZATION OF A MAJOR LATEX PROTEIN (MLP) GENE DOWN-REGULATED BY ETHYLENE DURING PEACH FRUITLET ABSCISSION. PLANT SCIENCE. 2002. V. 163. P. 265-272. Interpretive Summary: The shedding of plant organs is the result of the coordinated sequence of events leading to wall digestion in well-defined cell layers (abscission zone, AZ), which are targets for the abscission-inducing stimuli. We have isolated and sequenced the gene, DD1, from peach fruit AZs and have characterized its expression in various abscission and non-abscission peach tissues. We show that DD1 mRNA accumulates in specific cells associated with the vascular bundle in the fruitlet abscission zone, and its expression is repressed by ethylene. DD1 has homology to a class of proteins designated as "major latex proteins". The specific function of these proteins remains a mystery though they have been previously associated with fruit ripening and defense response.
Technical Abstract: We report the isolation of a new peach gene, Pp-MLP1, that shows significant similarity to a family of fruit- and flower-specific genes, designated as major latex protein (MLP) homologues. Transcript of Pp-MLP1 accumulated to high levels in cells of the fruit pedicel adjacent to the abscission zone (non-abscission zone), similar to lacticifers and, to a lesser extent, in epicotyls, stems and roots, while no accumulation was detected in leaves. In contrast to the MLP homologues isolated so far, the Pp-MLP1 transcript was detected during fruit cell expansion, though its expression appeared unrelated to fruit ripening. Propylene treatment caused a decrease in mRNA accumulation of Pp-MLP1 in all tested tissues. The function of Pp-MLP1, as with all previously described MLP homologues, is unknown. MLPs are associated with fruit and flower development in addition to plant pathogenesis responses. Expression in tissues associated with abscission would be consistent with a role in implementing this aspect of floral development or possibly protective responses to plant pathogens which may infect post-abscission wounds. In addition, the high similarity between proteins encoded by Pp-MLP1 and Csf2, an MLP gene associated with the early development of cucumber fruit, could suggest an alternative developmental role such as cell and tissue expansion.