Fig. 3: Evidence that SPX is an upstream negative regulator of AP and P transporters.

a Total AP activities in mSPX15-3 were higher than in WT. b Extracellular AP activities in mSPX15-3 were higher than in WT. Error bars, SD. Asterisks in (a, b) depict significant differences (n = 3; p < 0.05). c Changes in mRNA expression of AP, PT, and phospholipid degradation-related genes between SPX mutants (mSPX1-4 and mSPX15-3) and WT under P+ condition. Error bars, SD. Statistically significant changes (*) relates to comparison of mSPX with WT (n = 3; p < 0.05). d The putative model of SPX as an upstream negative regulator in P. tricornutum. Positive and negative effects are indicated by arrows and flat-ended lines, respectively.