Fig. 1
From: Dissection of MAPK signaling specificity through protein engineering in a developmental context
Schematic of stomatal lineage, indicating stages where MKK activation leads to similar and divergent outputs (based on [22]). Diagrams of MAPK signaling cascades, with each colored circle representing a different kinase level; circles are labeled with relevant kinase number, with orange circle representing MPK of unknown identity. Constitutive activation of YDA (MKKK), MKK5 or MKK7 inhibits stomatal lineage initiation (a, SPCH and MUTE stages). Late in the lineage (d, FAMA stage) YDA and MKK7, but not MKK5, activation leads to stomatal proliferation via an unidentified MPK. b, c, e, f Tracings of phenotypes resulting from activation of kinases. In (b–c), constitutively active MKK5 (MKK5DD) or MKK7 (MKK7ED) inhibit initiation (division of meristemoid mother cell (MMC) into meristemoid (M)) and lineage progression (conversion of M into guard mother cell (GMC)). In (e–f), MKK5DD has no effect (e, WT numbers and distribution of stomata in green), but MKK7ED induces guard cell (GC) overproliferation and clustering (f). Stages are referred to as SPCH, MUTE and FAMA after the promoters to drive expression of MAPK network components [22]. YDA, YODA; 5, MKK5; 7, MKK7; 3/6, MPK3 and MPK6