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), PLDz1 and PLDz2, were involved in root elongation during phosphate limitation. PLDz1 and PLDz2 are structurally different from the majority of plant PLDs by having phox and pleckstrin homology domains. Both PLDzs were expressed more in roots than in other tissues. It was reported previously that inducible suppression or inducible overexpression of PLDz1 affected root hair patterning. However, gene knockouts of PLDz1, PLDz2, or the double knockout of PLDz1 and PLDz2 showed no effect on root hair formation. The expression of PLDzs increased in response to phosphate limitation. The elongation of primary roots in PLDz1 and PLDz2 double knockout mutants was slower than that of wild type and single knockout mutants. The loss of PLDz2, but not PLDz1, led to a decreased accumulation of phosphatidic acid in roots under phosphate-limited conditions. These results indicate that PLDz1 and PLDz2 play a role in regulating root development in response to nutrient limitation.