2.1 Plant material and growth conditions
OsPHR2-Ov1 (an OsPHR2 -overexpressing transgenic plant),phr2 (an OsPHR2 T-DNA insertion mutant), and their corresponding wild-type O. sativa L. japonica Nipponbare (NIP) are as described (Zhou et al. , 2008; Guo et al. , 2015).OsMYC2 CRISPR/Cas9 mutants (designated as myc2 ) were generated on the NIP background. Germinated seeds were hydroponically cultured in normal rice culture solutions (Yoshida et al. , 1976) and incubated in a growth chamber under a 12-h-light (30 °C)/12-h-darkness (25 °C) photoperiod with 200 μmol m-2s-1 photon density and ~60% humidity. For Pi starvation (-P) conditions, the concentration of KH2PO4 was 0 μM, with phosphate buffer in the Pi-deficient medium replaced by equimolar amounts of KCl (Khan et al., 2016); the normal solution with 200 μM KH2PO4 was considered as Pi-sufficient (+P). The culture solution was adjusted to a pH of 5.4-5.6 using 1 M KOH, and the nutrient solution was replaced every other day during treatment.