Contribution of proteomics to the study of physiological aspects related to fruit tree productivity

Fruit trees provide important agricultural resources of high economic and nutritional value. The selection of rootstocks and fruit varieties assuring high yield and fruit quality greatly influences orchard productivity. In the last years, proteomics has contributed to the study of some relevant topics of tree physiology (Molassiotis et al, 2013), like fruit ripening, plant responses to abiotic stress and functionality of the graft union between rootstock and scion. Many proteomic studies have been conducted on fruit ripening in climacteric and non-climacteric species, among which Prunus spp. and Vitis vinifera (Li et al, 2017). Proteomics allowed to shed light on how the modulation of primary pathways, such as C metabolism and energy production, plays key roles in sustaining the biosynthesis of fruit secondary metabolites. Moreover, the metabolic strategies to sustain fruit biochemical changes during ripening seem to deeply influence the accumulation of other protein families, among which proteins involved in protein synthesis and stress responses (Negri et al, 2015; Prinsi et al, 2016). Proteomics has also been exploited to study plant responses to some of the main abiotic stresses that affect fruit trees, such as salinity and drought. In particular, new analytical strategies allowed the study of very recalcitrant samples obtained by highly lignified root systems. These approaches have proposed the involvement of different metabolic pathways and new proteins in stress perception, signaling and responses (Prinsi et al, 2018). Moreover, new studies concerning the biochemical processes involved in graft (in)compatibility have again emphasized the strong interconnections between primary and secondary metabolism. Interestingly, these studies put in evidence how proteomics could represent a promising approach to gain further knowledge about this physiological topic, which has a fundamental importance in orchard management (Prinsi et al, 2015).