The characterization of transgenic plants expressing the sunflower transcription factor HaHB4 uncovered a new role for the lateral auxin influx carrier LAX2 in venation patterning and xylem vasculature development. Most of single and multiple mutants for AUX/LAX genes presented an enhanced asymmetry in the venation patterning.
Additionally, Moreno-Piovano et al. show that LAX2 is a negative regulator of xylem vasculature, since the lax2 mutant exhibited increased xylem length and number of xylem cell rows. These results strongly indicated that auxin homeostasis influenced by LAX2 is required to achieve normal vascular development.