Regulation of Leaf Maturation by Chromatin-Mediated Modulation of Cytokinin Responses

Abstract

Plant shoots display indeterminate growth, while their evolutionary decedents, the leaves, are determinate. Determinate leaf growth is conditioned by the CIN-TCP transcription factors, which promote leaf maturation and which are negatively regulated by miR319 in leaf primordia. Here we show that CIN-TCPs reduce leaf sensitivity to cytokinin (CK), a phytohormone implicated in inhibition of differentiation in the shoot. We identify the SWI/SNF chromatin remodeling ATPase BRAHMA (BRM) as a genetic mediator of CIN-TCP activities and CK responses. An interactome screen further revealed that SWI/SNF complex components including BRM preferentially interacted with bHLH transcription factors and the bHLH-related CIN-TCPs. Indeed, TCP4 and BRM interacted in planta. Both TCP4 and BRM bound the promoter of an inhibitor of CK responses, ARR16, and induced its expression. Reconstituting ARR16 levels in leaves with reduced CIN-TCP activity restored normal growth. Thus, CIN-TCP and BRM together promote determinate leaf growth by stage-specific modification of CK responses.

Regulatory modules controlling maize inflorescence architecture

“…6A,B). Consistent with this hypothesis, down-regulation of TCP genes, as in ra mutants, has been shown to increase sensitivity to cytokinin (Efroni et al 2013).…”

SWP73 Subunits of Arabidopsis SWI/SNF Chromatin Remodeling Complexes Play Distinct Roles in Leaf and Flower Development

“…SWI/SNF, consisting of an SNF2 ATPase, two SWI3s, and an SNF5 subunit, is capable of nucleosome disruption through facilitation of reversible transition between normal (inaccessible) and altered (more accessible) conformations (Narlikar et al, 2002). In Arabidopsis thaliana, SWI/SNF complexes are involved in modulating various developmental and regulatory processes, including both vegetative and generative development, flowering time, and hormonal signaling (Sarnowski et al, 2005;Bezhani et al, 2007;Han et al, 2012;Archacki et al, 2013;Efroni et al, 2013;Sarnowska et al, 2013;Vercruyssen et al, 2014).…”

Fundamental and applied research in ABA signaling: Regulation by ABA of the chromatin remodeling ATPase BRAHMA and biotechnological use of the PP2CA promoter.

“…SWI2 and SNF2 genes were originally discovered in Saccharomyces cerevisiae by screening for mutants affected in mating-type switch (Switch) and ability to growth on carbon sources other than glucose (Sucrose non-fermenting) (Abrams et al, 1986). In Arabidopsis thaliana, SWI/SNF complexes are involved in modulating various developmental and regulatory processes, including both vegetative and generative development, flowering time and hormonal signaling (Sarnowski et al, 2005, Bezhani et al, 2007, Saez et al, 2008, Han et al, 2012, Archacki et al, 2013, Efroni et al, 2013, Sarnowska et al, 2013, Vercruyssen et al, 2014, Zhao et al, 2015a.…”

“…This HSA domain frequently serves as docking site for recruiting transcription factors such as LFY and TCP4 (Farrona et al, 2004, Szerlong et al, 2008, Efroni et al, 2013. The HSA domain is followed by the catalytic helicase-like ATPase domain and the Snf2 ATP-coupling (SnAC) domain, which is very important for catalytic activity of BRM.…”

“…In plants and mammals, SWI/SNF subfamily of chromatin remodelers are required to promote both stem cells fate and differentiation (Farrona et al, 2004, Tang et al, 2008, Farrona et al, 2011, Efroni et al, 2013, Vercruyssen et al, 2014, Zhao et al, 2015a. BRM has been proposed as a regulator of the root cell stem niche through alteration of auxin distribution.…”