The establishment of abaxial-adaxial polarity in lateral organs involves fa
ctors intrinsic to the primordia and interactions with the apical meristem
from which they are derived. Recently, a small plant-specific family of gen
es, the YABBY gene family, has been proposed to specify abaxial cell fate.
Each asymmetric above-ground lateral organ expresses at least one member of
the family in a polar manner, and loss- and gain-of-function studies indic
ate that they are sufficient to specify abaxial cell fate and that they act
in both distinct and redundant manners.