Overexpression of a putative Arabidopsis BAHD acyltransferase causes dwarfism that can be rescued by brassinosteroid

Abstract

Plant growth and development are ensured through networks of complex regulatory schemes. Genetic approaches have been invaluable in dissecting these regulatory pathways. This study reports the isolation of a semi-dominant dwarf mutant designated abnormal shoot1-1 dominant (abs1-1D) through an Arabidopsis T-DNA activation tagging mutant screen. It was shown that the overexpression of a novel BAHD family acyltransferase gene, ABS1/At4g15400, was the cause of the dwarf phenotype in abs1-1D. Overexpression of ABS1 led to many phenotypic features reminiscent of brassinosteroid (BR) deficient or signalling mutants, and it was shown that exogenously applied BR could effectively rescue the dwarf phenotype of abs1-1D. Furthermore, genetic analyses indicated that abs1-1D interacted, in different ways, with the BR-deficient mutant det2-1, the constitutive BR response mutant bes1-D and the photomorphogenic mutant phyB-1. Moreover, ABS1 expression was activated by BR treatment or in a bes1-D mutant background. Genome-wide transcriptome profiling of abs1-1D revealed clear reprogramming of metabolic pathways, and it was demonstrated that BR biosynthesis genes were activated in abs1-1D and that the flavonoid biosynthesis pathway was repressed in abs1-1D, as well as in det2-1. This work provides new insights into the possible involvement of BAHD acyltransferase in the regulation of plant growth and development, and indicates a possible role of ABS1 in maintaining BR homeostasis.

From Squalene to Brassinolide: The Steroid Metabolic and Signaling Pathways across the Plant Kingdom

“…Recently, two additional enzymes, namely BRASSINOS-TEROID INACTIVATOR 1 (BIA1)/ABNORMAL SHOOT1 (ABS1) and BR-RELATED ACTYLTRANSFERASE1 (BAT1)/PIZZA (PIZ) that were characterized as putative acyltransferases, were shown to modulate BR levels in Arabidopsis (Choi et al, 2012;Roh et al, 2012;Schneider et al, 2012;Wang et al, 2012a). Results of in vivo feeding and in vitro biochemical assays suggest that BRI1-5 ENHANCED1 (BEN1), an Arabidopsis gene encoding a dihydroflavonol 4-reductase (DFR)-like protein, an enzyme presumably involved in the flavonoid pathway, is also involved in BR inactivation (Yuan et al, 2007).…”

CCA1 and ATAF2 differentially suppress cytochrome P450-mediated brassinosteroid inactivation in Arabidopsis

“…BR inactivation can be achieved via multiple approaches in Arabidopsis , including hydroxylation (Neff et al ., 1999; Turk et al ., 2003), glycosylation (Poppenberger et al ., 2005; Husar et al , 2011), acylation (Roh et al ., 2012; Wang et al ., 2012a; Schneider et al ., 2012b; Zhu et al ., 2013b; Choi et al ., 2013; Zhang and Xu, 2018), and other unknown or unconfirmed mechanisms (Turk et al ., 2005; Takahashi et al ., 2005; Nakamura et al ., 2005; Yuan et al ., 2007; Marsolais et al ., 2007; Thornton et al ., 2010; Sandhu and Neff, 2013). At least ten BR-inactivating genes have been identified in Arabidopsis including; P450 hydroxylases, glycosyltransferases, acyltransferases, sulfotransferases and a reductase.…”

Occurrence of phosphorylated castasterone in Arabidopsis thaliana and Lycopersicum esculentum

“…These results indicate that the enzyme responsible for phosphorylation of BR, namely BR kinase, is likely specific for CS in both plants. In Arabidopsis thaliana, several genes involved in BR conjugation, such as UGT73C5 and UGT73C6 for glucosylation (Poppenberger et al 2005, Husar et al 2011, ST4 and ST1 for sulfonation (Marsolais et al 2007) and BAHD and BAT1/DRL1/PIZZA for acylation (Roh et al 2012, Schneider et al 2012, Wang et al 2012, Choi et al 2013, Zhu et al 2013, have been identified. Overexpression of these genes altered the endogenous levels of BRs, most likely due to the reduction of the amounts of CS and BL, and exhibited abnormal growth and development, which was observed in BR-deficient Arabidopsis mutants.…”