PEG induces maturation of somatic embryos of Passiflora edulis Sims ‘UENF Rio Dourado’ by differential accumulation of proteins and modulation of endogenous contents of free polyamines

Abstract Sour passion fruit (Passiflora edulis Sims) has economic and social relevance and is an alternative crop mainly for family farming agriculture. The aim of this work was to evaluate the influence of polyethylene glycol (PEG) on the maturation of somatic embryos associated with differential accumulation of proteins and changes in the endogenous polyamine (PA) content during somatic embryogenesis of P. edulis ‘UENF Rio Dourado’. Maturation of somatic embryos was performed using embryogenic callus in MS culture medium with PEG 6% or without PEG (control). PEG 6% promoted the maturation of a significantly higher number of somatic embryos at globular and cotyledonary stages when compared to the control treatment. The higher somatic embryo formation induced by PEG 6% was associated with an increase in endogenous contents of free spermine, a PA with an important role in the maturation process of somatic embryogenesis cultures. PEG also promoted a significantly higher content of putrescine and total free PAs at the end of maturation, which was relevant for the increase in the number of somatic embryos. Comparative proteomic analyses of PEG 6%/control revealed that PEG 6% treatment induced the up-accumulation of proteins related to the ATP metabolic, glycolytic, generation of precursor metabolite energy, and the response to light stimulus processes. The down-accumulated proteins were related mainly to the cellular metabolic process. The use of PEG induced the maturation and development of somatic embryos of P. edulis Sims ‘UENF Rio Dourado’ by the differential accumulation of proteins and modulation of endogenous contents of PAs.