BAT1, a putative acyltransferase, modulates brassinosteroid levels in Arabidopsis

Abstract

SUMMARYBrassinosteroids (BRs) are essential for various aspects of plant development. Cellular BR homeostasis is critical for proper growth and development of plants; however, its regulatory mechanism remains largely unknown. BAT1 (BR-related acyltransferase 1), a gene encoding a putative acyltransferase, was found to be involved in vascular bundle development in a full-length cDNA over-expressor (FOX) screen. Over-expression of BAT1 resulted in typical BR-deficient phenotypes, which were rescued by exogenously applied castasterone and brassinolide. Analyses of BR profiles demonstrated that BAT1 alters levels of several brassinolide biosynthetic intermediates, including 6-deoxotyphasterol, typhasterol and 6-deoxocastasterone. BAT1 is mainly localized in the endoplasmic reticulum. BAT1 is highly expressed in young tissues and vascular bundles, and its expression is induced by auxin. These data suggest that BAT1 is involved in BR homeostasis, probably by conversion of brassinolide intermediates into acylated BR conjugates.

Spatiotemporal Brassinosteroid Signaling and Antagonism with Auxin Pattern Stem Cell Dynamics in Arabidopsis Roots

“…A role of BR catabolism in patterning BZR1 is confirmed by the increased nuclear BZR1 levels in the QC and stem cell regions of the bas1;sob7 double mutant, which is defective in two BR-inactivating enzymes expressed in the root tip region. A recent study showed that another BR-inactivating enzyme, BAT1, is also expressed in the root tip region [45]. While BR synthesis and catabolism are required for normal BZR1 patterning, differential BR sensitivity may also contribute to the BZR1 patterning, as BR treatment and the bzr1-1D mutation reduced, but did not completely abolish, the BZR1 gradient.…”

“…Indeed, auxin treatment increased cytoplasmic localization of BZR1 in the elongation zone, and inhibiting auxin biosynthesis increased nuclear BZR1 in the root tip region, where the endogenous auxin level is at a maximum. Auxin increases the expression levels of several BR catabolic enzymes, including BAS1, SOB7, BAT1, and BEN1 (Table S4; [45]). These observations suggest that the auxin gradient contributes to the complementary pattern of nuclear BZR1 in root tip, at least in part by promoting local BR catabolism.…”

The Regulation of Brassinosteroid Biosynthesis in Arabidopsis

“…Pending biochemical confirmation, BAHD acyltransferases, such as BIA1 and PIZ, might act redundantly in BR inactivation. Additionally, BAT1 (putative BR-related acyltransferase), a putative acyltransferase involved in BR inactivation, was identified by the FOX hunting technique (Choi et al, 2013). The BAT1 overexpression line showed a substantial decrease in the level of 6-deoxoTY, TY, and 6-deoxoCS, and exhibited a growth-retarded phenotype, as seen in the BR dwarf mutants.…”

The Unique Role of the ECERIFERUM2-LIKE Clade of the BAHD Acyltransferase Superfamily in Cuticular Wax Metabolism

“…The subclade in blue was used for the tree-reconciliation analysis ( A ). Characterized BAHD acyltransferases from Arabidopsis are numbered, clockwise, and marked on the tree with orange circles; (1) At5g48930, HCT/HYDROXYCINNAMOYL-COA SHIKIMATE/QUINATE HYDROXYCINNAMOYL TRANSFERASE [62]; (2) At2g19070, SHT/SPERMIDINE HYDROXYCINNAMOYLTRANSFERASE [63]; (3) At5g41040, ASFT/ALIPHATIC SUBERIN FERULOYL TRANSFERASE [64]; (4) At3g48720, DCF/DEFICIENT IN CUTIN FERULATE [32]; (5) At5g63560, FACT/FATTY ALCOHOL:CAFFEOYL-COA CAFFEOYL TRANSFERASE [65]; (6) At1g65450, GLC/GLAUCE [66]; (7) At4g31910, DRL/DWARF AND ROUND LEAF 1 [67]/BAT1/BR-RELATED-ACYLTRANSFERASE [68]/PIZ/PIZZA [69]; (8) At3g29670, PMAT2/PHENOLIC GLUCOSIDE MALONYLTRANSFERASE 2 [70]; (9) At5g67160, EPS2/ENHANCED PSEUDOMONAS SUSCEPTIBILITY 1 [71]. The full gene tree (with complete gene identifiers and scale) is provided in the supplemental information.…”