Double knockouts of phospholipases Dζ1 and Dζ2 in Arabidopsis affect root elongation during phosphate-limited growth but do not affect root hair patterning

Root elongation and root hair formation are important in nutrient absorption. We found that two Arabidopsis (Arabidopsis thaliana) phospholipase Ds (PLDs), PLD zeta 1 and PLD zeta 2, were involved in root elongation during phosphate limitation. PLD zeta 1 and PLD zeta 2 are structurally different from the majority of plant PLDs by having phox and pleckstrin homology domains. Both PLD zeta s were expressed more in roots than in other tissues. It was reported previously that inducible suppression or inducible overexpression of PLD zeta 1 affected root hair patterning. However, gene knockouts of PLD zeta 1, PLD zeta 2, or the double knockout of PLD zeta 1 and PLD zeta 2 showed no effect on root hair formation. The expression of PLD zeta s increased in response to phosphate limitation. The elongation of primary roots in PLD zeta 1 and PLD zeta 2 double knockout mutants was slower than that of wild type and single knockout mutants. The loss of PLD zeta 2, but not PLD zeta 1, led to a decreased accumulation of phosphatidic acid in roots under phosphate-limited conditions. These results indicate that PLD zeta 1 and PLD zeta 2 play a role in regulating root development in response to nutrient limitation.