Modulation of Phospholipid Signaling by GLABRA2 in Root-Hair Pattern Formation

The root-hair pattern of Arabidopsis is determined through a regulatory circuit composed of transcription factor genes. The homeobox gene GLABRA2 ( GL2 ) has been considered a key component, acting farthest downstream in this regulation. GL2 modified to include a transactivating function caused epidermal cells to develop ectopic root hairs or root hair–like structures. With this system, the phospholipase Dζ1 gene ( AtPLD ζ 1 ) was identified as a direct target of GL2. Inducible expression of AtPLD ζ 1 promoted ectopic root-hair initiation. We conclude that GL2 exerts its regulatory effect on root-hair development through modulation of phospholipid signaling.