Abscisic acid signaling is controlled by a BRANCHED1/HD-ZIP I cascade in Arabidopsis axillary buds

Abstract

Shoot-branching patterns determine key aspects of plant life and are important targets for crop breeding. However, we are still largely ignorant of the genetic networks controlling locally the most important decision during branch development: whether the axillary bud, or branch primordium, grows out to give a lateral shoot or remains dormant. Here we show that, inside the buds, the TEOSINTE BRANCHED1, CYCLOIDEA, PCF (TCP) transcription factor BRANCHED1 (BRC1) binds to and positively regulates the transcription of three related Homeodomain leucine zipper protein (HD-ZIP)-encoding genes: HOMEOBOX PROTEIN 21 (HB21), HOMEOBOX PROTEIN 40 (HB40), and HOMEOBOX PROTEIN 53 (HB53). These three genes, together with BRC1, enhance 9-CIS-EPOXICAROTENOID DIOXIGENASE 3 (NCED3) expression, lead to abscisic acid accumulation, and trigger hormone response, thus causing suppression of bud development. This TCP/HD-ZIP genetic module seems to be conserved in dicot and monocotyledonous species to prevent branching under light-limiting conditions.

Ideal crop plant architecture is mediated by tassels replace upper ears1, a BTB/POZ ankyrin repeat gene directly targeted by TEOSINTE BRANCHED1

“…gt1 was also found to be genetically downstream of tb1 (52), and is likely another TB1 target. In addition, recent work in Arabidopsis showed that gt1 homologs are directly targeted by BRC1, and regulate ABA levels and signaling (53). Both gt1 and tru1 independently control a subset of phenotypes seen in tb1, where gt1 represses tiller number at ground level, while tru1 represses axillary bud growth aboveground, without affecting tillering (Fig.…”

Mechanisms of vegetative propagation in bulbs : a molecular approach

“…TB1(monocots)/BRC1(dicots) is a TCP transcription factor mainly expressed in dormant axillary meristems inhibiting their outgrowth Takeda et al 2003;Hubbard et al 2002). Given the role of TB1/BRC1 as integrator of multiple signals involved in bud outgrowth, mayor attention has been given to this gene in recent years (Martín-Trillo et al 2011;Nicolas et al 2015;Braun et al 2012;González-Grandío et al 2017).…”

“…However, the buds that are initiated when the shoot apical meristem (SAM) of their mother has transitioned into the reproductive state ('A and B' buds in tulip), are able to skip this kind of dormancy (Chapter 4 and (Rees 1968)). This particular dormancy is known as paradormancy and imposed by apical dominance (Lang et al 1987 (Yao and Finlayson 2015;González-Grandío et al 2017;GomezRoldan et al 2008;Liang et al 2010;Pasare et al 2013;González-Grandío and Cubas 2014;Wu et al 2015;Hartmann et al 2011). …”

“…Auxin seems to interact with the hormone strigolactone to inhibit bud growth (Bennett and Leyser 2006;Brewer et al 2009;Liang et al 2010), while cytokinins directly activate outgrowth (Dun et al 2012;Shimizu-Sato and Mori 2001). Additionally, two other classical and antagonistic acting hormones, gibberellin and abscisic acid, involved in seed dormancy release and dormancy induction maintenance respectively, also seem to play a role in the control of axillary bud development and branching (Elfving et al 2011;Jiang et al 2009;Reddy et al 2013;Yao and Finlayson 2015;González-Grandío et al 2017). …”

Plant transcription factors from the homeodomain‐leucine zipper family I. Role in development and stress responses

“…The current knowledge about HD‐Zip I TFs was acquired by different techniques including sequencing, next generation sequencing, expression patterns and characterization of overexpressing and/or mutant plants, among others . This knowledge helped to understand the regulation of gene expression in plants as well as to discover signal transduction pathways.…”