Gene-editing the two homologs of the core stomatal transcription factor MUTE disrupted stomatal formation and messed up asymmetric divisions - a first hint that Kalanchoë MUTE has a different role in leaf succulents than Arabidopsis. 4/n
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Indeed, fluorescent reporter genes showed that both MUTE homologs are expressed specifically during the asymmetric divisions forming SCs. This suggested that MUTE might be involved in controlling SC divisions. 5/n
When overexpressing Kalanchoë MUTE, many additional subsidiary-cell-like cells were formed in Kalanchoë. This is strikingly different from the MUTE overexpression phenotype in Arabidopsis, where many additional guard cells pairs rather than subsidiary cells are formed. 6/n
This suggested that MUTE in the leaf succulent Kalanchoë makes subsidiary cells. Strikingly, this is more similar to MUTE’s role in the distantly related grasses than in the more closely related Arabidopsis. 7/n
Finally, we used transcriptomics to detect the deregulated downstream genes when Kalanchoë MUTE is overexpressed. Unlike in Arabidopsis, genes linked to asymmetric divisions are upregulated and genes linked to guard cell differentiation are downregulated. 8/n
Together, we propose that much like in grasses, Kalanchoë MUTE makes stomatal subsidiary cells by delaying the guard cell program and inducing an asymmetric division program. 9/n
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