Proteomic study of 'Moncada' mandarin buds from on- versus off-crop trees

A proteomic analysis of buds from mandarin trees with contrasting fruit load (on- and off-crop trees) was carried out during the onset of low-temperature induction. The aim of the study was to find out more about the molecular mechanism relating to alternate bearing in Citrus and its relationship with flowering. The 'Moncada' variety (Clementine 'Oroval' x 'Kara' mandarin), displaying remarkable behaviour in alternate production, was used in this study. From 2D DICE gel, 192 spots were isolated: 97 showed increased expression in the off-crop buds as compared to the on-crop buds, while 95 exhibited enhanced expression in the on-crop buds versus the off-crop buds. These spots were identified by MALDI-MS or LC -MS-MS. The largest groups of proteins up-expressed in the off-crop buds were the proteins involved in carbohydrate and amino acid metabolism, and the proteins expressed in response to stimuli such as reactive oxygen species. The largest groups of proteins up-expressed in the on-crop buds were related to primary metabolism, oxidative stress and defence responses. Depending on their function, some of these proteins can stimulate the flowering, such as fructose-bisphosphate aldolase or leucine-rich repeat transmembrane protein kinase, while others can inhibit it, such as cytochrome c oxidase subunit II. Twenty-two other proteins with unknown functions were up-expressed in the on- or off-crop buds. (C) 2013 Elsevier Masson SAS. All rights reserved.
M.C. Gonzalez-Mas was the recipient of a contract by the Fundacion AgroAlimed (Conselleria d'Agricultura, Pesca i Alimentacio, Generalitat Valenciana). This work has been supported by grants from the Instituto Nacional de Investigaciones Agrarias, Spain (RTA2009-00147, RTA2011-00114-00-00). The DIGE were performed by the Proteomic Service of the Instituto de Biologia Molecular y Celular de Plantas (UPV-Valencia). Mass analyses were carried out in the Proteomic Laboratory of CIPF (a ProteoRed_ISCIII member; the Spanish Proteomics Network); special thanks are due to Dr. L. Valero and E. Dionis for assistance and advice on mass analyses.