PLTs are expressed in the LT cells by the 8-cell stage, while HD-ZIPIII begin to be expressed in the UT cells at the 16-cell stage. MicroRNAs (165/166) are involved in post-transcriptional regulation of the HD-ZIPIIIs. In the tpl-1 mutant, the PLT genes become misregulated and are expressed at both poles of the embryo. The most severe phenotype is the transformation of the shoot into a root. Conversely, if forms of the HD-ZIPIII genes that cannot be regulated by MIR165/166 are expressed in the LT cells, using the PLT2 promoter sequences, the root is transformed into a shoot. Data presented from [117,118].