Characterisation of the phytase gene in trifoliate orange ( Poncirus trifoliata (L.) Raf.) seedlings

•Trifoliate orange could utilise phytin without microorganisms in P-deficient conditions by promoting phytase and acid phosphatase activity.•The expressions of the three predicted acid phosphatase genes (PtPAP1, PtPAP2, PtPAP3) of trifoliate orange were up-regulated in roots and leaves with –P solutions.•The Km values of the recombinant protein (r-PtPAP3) which was expressed in Pichia pastoris were 46.2μM for phytate and 1631μM for ρ-nitrophenylphosphate.