PSY gene evolutionary scenario in Angiosperms. The modern monocots (exemplified by the rice genome structured in 12 chromosomes) and eudicots (exemplified by the grape genome structured in 19 chromosomes) are illustrated at the bottom using a color code that reflect the ancestral genome structure of respectively 5 and 7 protochromosomes according to Abrouk et al.. The angiosperm ancestor may contain two PSY gene copies, i.e. PSY 1 and PSY 2. The two copies are located on the protochromosomes A10 and A19 of the eudicot ancestor and both retained in single copies during the WGD shared by the eudicots. In modern eudicots, the PSY gene family is structured in two copies, i.e. PSY 1 and PSY 2. In monocots PSY 1 has been duplicated during a first WGD (referenced as 1) so that the monocot ancestral genome contains three PSY gene copies, i.e. PSY 1, PSY 2 and PSY 3. The three PSY genes are located on ancestral chromosomes A4, A11 and A8 and all retained in single copies during the WGD shared by the monocots (referenced as 2). In modern monocots, the PSY gene family is structured in three copies, i.e. PSY 1, PSY 2 and PSY 3.