Data from: FAMA is an essential component for the differentiation of two distinct cell types, myrosin cells and guard cells, in Arabidopsis

Brassicales plants, including Arabidopsis thaliana, have an ingenious
two-compartment defense system, which sequesters myrosinase from the
substrate glucosinolate and produces a toxic compound when cells are
damaged by herbivores. Myrosinase is stored in vacuoles of idioblast
myrosin cells. The molecular mechanism that regulates myrosin cell
development remains elusive. Here, we identify the basic helix-loop-helix
transcription factor FAMA as an essential component for myrosin cell
development along Arabidopsis leaf veins. FAMA is known as a regulator of
stomatal development. We detected FAMA expression in myrosin cell
precursors in leaf primordia in addition to stomatal lineage cells. FAMA
deficiency caused defects in myrosin cell development and in the
biosynthesis of myrosinases THIOGLUCOSIDE GLUCOHYDROLASE1 (TGG1) and TGG2.
Conversely, ectopic FAMA expression conferred myrosin cell characteristics
to hypocotyl and root cells, both of which normally lack myrosin cells.
The FAMA interactors ICE1/SCREAM and its closest paralog SCREAM2/ICE2 were
essential for myrosin cell development. DNA microarray analysis identified
32 candidate genes involved in myrosin cell development under the control
of FAMA. This study provides a common regulatory pathway that determines
two distinct cell types in leaves: epidermal guard cells and inner-tissue
myrosin cells.