Interactions among gibberellins, brassinosteroids and genes regulate stomatal development in the Arabidopsis hypocotyl.

Stomata are pores on the plant surface that enable gas exchange with the atmosphere. In Arabidopsis thaliana, brassinosteroids, which function upstream of the TTG/bHLHs/MYBs/GL2 transcriptional network, positively regulate stomatal formation in the hypocotyl. Gibberellins also promote stomatal development in the embryonic stem. Here, we investigated the hypothetical interactions between the gibberellin and brassinosteroid signaling pathways during stomatal formation. By combining genetics and gene expression studies, we found that gibberellins promote stomatal development, functioning upstream of both brassinosteroids and the TTG/bHLHs/MYBs/GL2 network. Gibberellins also regulate an earlier step in stomatal development than that regulated by the receptor-like membrane protein TOO MANY MOUTHS.