Identification, cloning, and expression analysis of three phytoene synthase genes from Cucurbita pepo

An essential step in the carotenoid biosynthesis pathway is the formation of phytoene by phytoene synthase (PSY). In this study, three new genes coding PSYs (CpPSYA, CpPSYB, and CpPSYC) were cloned from Cucurbita pepo and their expression patterns analysed in three cultivars of summer squash which had a different carotenoid content. The gene sequences had a high similarity with those from other plant species, and their predicted proteins were significantly different from each other. A phylogenetic analysis indicates that CpPSYA and CpPSYB shared a high homology and were also homologous with PSYs from others cucurbits, whereas CpPSYC was more closely related to orthologues from strawberry and carrot. An expression analysis revealed that CpPSYA had a higher expression in flowers compared to leaves and showed a differential expression during fruit development. The amount of CpPSYA transcript was higher in fruits with a higher carotenoid content than in those with a lower carotenoid content. However, CpPSYB and CpPSYC showed a relatively high expression in leaves, and their expression in fruits varied among the different cultivars and fruit tissues. These results suggest that the CpPSY genes were under different regulatory mechanisms and they may have different roles in C. pepo.A financial support was provided by the Spanish Project INIA-RTA2011-00044-C02-01, FEDER and FSE funds. Á. Obrero had a contract from INIA-IFAPA (Subprograma FPI-INIA), co-financed by FSE funds (Programa Operativo FSE de Andalucía 2007–2013 “Andalucía se mueve con Europa”). The New Zealand Institute for Plant and Food Research Limited hosted Á. Obrero for a short stay, where part of this work was done. C.I. González Verdejo wish to thank the National Institute of Agricultural Research (INIA) and FSE funds for contract funding.Peer reviewe