(A) flg22-induced MAPK activation in Col-0 and fer-4 mutant roots under Pi-starvation conditions. Seedlings grown in either HP or LP media were treated with 1 μM flg22 for 15 mins and roots were harvested. The MAPK level was determined with anti-pMAPK, and β-actin was used as a loading control. Data information: All experiments were repeated three times with similar results.  