Fig. 7. A model showing the regulatory relationship between LeT6 and LePHAN and final leaf morphology in tomato. LeT6 is downregulated when LePHAN is strongly overexpressed. Loss of KNOX gene function or extreme downregulation of LeT6 could be lethal for plants because of the lack of SAM formation/maintenance. Weak LePHAN overexpression might lead to the ectopic leaf blade outgrowth in the rachis region and make large simple leaves. LePHAN and LeT6 levels are well balanced in the wild-type leaf, producing 8-9 leaflets with normal ab-adaxiality. Weak LeT6 overexpression and LePHAN downregulation lead to KNOX overexpression phenotypes seen in the 35S::LeT6 plants (Janssen et al., 1998), Me/+ and Cu leaves. Because LeT6 overexpression phenotypes require LePHAN activity, strong LeT6 overexpression and LePHAN downregulation cause LePHAN downregulation phenotypes including cup-shaped or wire-like leaves, severe 35S::LeT6, Me/Me, w6/w6 and Cu/Cu;antiLePHAN/+ leaves.

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