The gene MACCHI-BOU 4/ENHANCER OF PINOID encodes a NPH3-like protein and reveals similarities between organogenesis and phototropism at the molecular level.

Intercellular transport of the phytohormone auxin is a significant factor for plant organogenesis. To investigate molecular mechanisms by which auxin controls organogenesis, we analyzed the macchi-bou 4 (mab4) mutant identified as an enhancer of pinoid (pid). Although mab4 and pid single mutants displayed relatively mild cotyledon phenotypes, pid mab4 double mutants completely lacked cotyledons.

The gene ENHANCER OF PINOID controls cotyledon development in the Arabidopsis embryo.

During Arabidopsis embryo development, cotyledon primordia are generated at transition stage from precursor cells that are not derived from the embryonic shoot apical meristem (SAM). To date, it is not known which genes specifically instruct these precursor cells to elaborate cotyledons, nor is the role of auxin in cotyledon development clear. In laterne mutants, the cotyledons are precisely deleted, yet the hypocotyl and root are unaffected.