FAMA Is an Essential Component for the Differentiation of Two Distinct Cell Types, Myrosin Cells and Guard Cells, in Arabidopsis  . Issue 10 (10th October 2014)

• Record Type: Journal Article
• Authors: Shirakawa, Makoto; Ueda, Haruko; Nagano, Atsushi J.; Shimada, Tomoo; Kohchi, Takayuki; Hara-Nishimura, Ikuko
• Is Part Of: The Plant Cell. Volume 26:Issue 10(2014)
• Page Start: 4039
• Page End: 4052
• Publication Date: 2014-10-10
• DOI: 10.1105/tpc.114.129874
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : This work shows that the guard cell master regulator FAMA has a role in idioblast myrosin cell differentiation in Arabidopsis . Brassicales plants evolved a common regulatory pathway for specification of two distinct types of leaf cells: epidermal guard cells for gas exchange and myrosin cells in leaf inner tissue for defense. Abstract: 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.