Arabidopsis BRASSINOSTEROID INACTIVATOR2 is a typical BAHD acyltransferase involved in brassinosteroid homeostasis

Abstract

Brassinosteroids (BRs) are plant-specific steroidal hormones; BR homeostasis is crucial for various aspects of plant growth and development. However, to date, the BR inactivation process has not been thoroughly elucidated. In this study, we identified and characterized a novel BAHD family acyltransferase gene, BRASSINOSTEROID INACTIVATOR2 (BIA2), involved in BR inactivation. BIA2-overexpressing (OE-BIA2) plants displayed typical BR-deficient phenotypes, which were rescued by exogenous BR treatment. Real-time qRT-PCR and transcriptome analyses showed that expression levels of virtually all of the BR biosynthetic genes were increased, whereas the expression of many BR inactivation genes was reduced in OE-BIA2 plants. Root inhibition assays showed that the root growth of OE-BIA2 plants was inhibited. We obtained plants with an intermediate phenotype by crossing the OE-BIA2 plants with BRASSINOSTEROID-INSENSITIVE1 (BRI1)-overexpressing plants. The null BIA2 mutants had longer hypocotyls in the dark. BIA2 was predominantly expressed in roots, and its expression was induced by 24-epibrassinolide or dark treatment, but it exhibited a differential expression pattern compared with its homologue, BIA1. Furthermore, genetic transformation with point-mutant and deleted-BIA2 constructs confirmed that the HXXXD motif is essential for the function of BIA2. Taken together, these findings indicate that BIA2 is a typical BAHD acyltransferase that is involved in BR homeostasis and may inactivate bioactive BRs by esterification, particularly in roots and hypocotyls under dark conditions.

CIRCADIAN CLOCK ASSOCIATED 1 and ATAF2 differentially suppress cytochrome P450-mediated brassinosteroid inactivation

“…Schneider et al, 2012;Choi et al, 2013;W. Zhu et al, 2013;Zhang and Xu, 2018), and other unknown or unconfirmed mechanisms (Nakamura et al, 2005;Takahashi et al, 2005;Turk et al, 2005;Marsolais et al, 2007;Yuan et al, 2007;Thornton et al, 2010;Sandhu and Neff, 2013). At least 10 BR-inactivating genes have been identified in Arabidopsis including; P450 hydroxylases, glycosyltransferases, acyltransferases, sulfotransferases, and a reductase.…”

Genome-wide comparative analysis of the BAHD superfamily in seven Rosaceae species and expression analysis in pear (Pyrus☓ bretschneideri)

“…The BAHD superfamily has members in various ester synthetic pathways. The functions of several BAHD genes have been reported [43][44][45]. Here, by detecting their HXXXD and DFGWG motifs using a HMMER search, we identified 717 BAHD genes from seven Rosaceae species.…”

“…For example, the BAHD acyltransferase gene can enhance saccharification [44], catalyzes the last step in cocaine biosynthesis [60], and the protein plays an important role in plant innate immunity [61]. Furthermore, AAT gene functions have been determined in several species.…”

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.…”