Arabidopsis acyl‐CoA‐binding protein ACBP1 participates in the regulation of seed germination and seedling development

Abstract

SUMMARYA family of six genes encoding acyl-CoA-binding proteins (ACBPs), ACBP1-ACBP6, has been characterized in Arabidopsis thaliana. In this study, we demonstrate that ACBP1 promotes abscisic acid (ABA) signaling during germination and seedling development. ACBP1 was induced by ABA, and transgenic Arabidopsis ACBP1-over-expressors showed increased sensitivity to ABA during germination and seedling development, whereas the acbp1 mutant showed decreased ABA sensitivity during these processes. Subsequent RNA assays showed that ACBP1 over-production in 12-day-old seedlings up-regulated the expression of PHOS-PHOLIPASE Da1 (PLDa1) and three ABA/stress-responsive genes: ABA-RESPONSIVE ELEMENT BINDING PROTEIN1 (AREB1), RESPONSE TO DESICCATION29A (RD29A) and bHLH-TRANSCRIPTION FACTOR MYC2 (MYC2). The expression of AREB1 and PLDa1 was suppressed in the acbp1 mutant in comparison with the wild type following ABA treatment. PLDa1 has been reported to promote ABA signal transduction by producing phosphatidic acid, an important lipid messenger in ABA signaling. Using lipid profiling, seeds and 12-day-old seedlings of ACBP1-over-expressing lines were shown to accumulate more phosphatidic acid after ABA treatment, in contrast to lower phosphatidic acid in the acbp1 mutant. Bimolecular fluorescence complementation assays indicated that ACBP1 interacts with PLDa1 at the plasma membrane. Their interaction was further confirmed by yeast two-hybrid analysis. As recombinant ACBP1 binds phosphatidic acid and phosphatidylcholine, ACBP1 probably promotes PLDa1 action. Taken together, these results suggest that ACBP1 participates in ABA-mediated seed germination and seedling development.

Interactions between Arabidopsis acyl-CoA-binding proteins and their protein partners

“…This model can explain the increase in ABA sensitivity of AtACBP1-overexpressors during seed germination and seedling development (Fig. 2b) (Du et al 2013a). …”

“…PLDa1 is a membrane phospholipase, producing phosphatidic acid (PA) (Fan et al 1999), and its activity can be stimulated by abscisic acid (ABA) (Zhang et al 2004). It has been shown that AtACBP1 overexpression in Arabidopsis enhances PLDa1 expression in response to ABA treatment (Du et al 2013a). (Meng et al 2011) Given that recombinant AtACBP1 binds PA and phosphatidylcholine (PC) in vitro Du et al 2010Du et al , 2013a and that AtACBP1 interacts with PLDa1 at the plasma membrane (Du et al 2013a), AtACBP1 possibly promotes hydrolysis of PC to PA as a result of an increase in PLDa1 expression (Fig.…”

“…Another ankyrin repeat-containing AtACBP, AtACBP1, has been recently reported to interact with PHOSPHOLI-PASE Da1 (PLDa1) at the plasma membrane by bimolecular fluorescence complementation (BiFC) and yeast two-hybrid assays (Du et al 2013a). PLDa1 is a membrane phospholipase, producing phosphatidic acid (PA) (Fan et al 1999), and its activity can be stimulated by abscisic acid (ABA) (Zhang et al 2004).…”

“…In addition, AtACBPs containing ankyrin repeats (AtACBP1 and AtACBP2) and kelch motifs (AtA-CBP4) have been observed to interact with protein partners, some of which have also turned out to be stress-responsive proteins Li et al 2008;Gao et al 2009Gao et al , 2010Licausi et al 2011;Du et al 2013a). …”

“…In recent years, increasing evidence has revealed that AtACBPs are involved in many biological processes, such as plant development Du et al 2013a), leaf senescence , pathogen resistance (Xiao and Chye 2011b) and response to environmental stresses (Chen et al 2008;Du et al 2010Du et al , 2013b including oxidative and heavy metal stresses Gao et al 2009Gao et al , 2010. In addition, AtACBPs containing ankyrin repeats (AtACBP1 and AtACBP2) and kelch motifs (AtA-CBP4) have been observed to interact with protein partners, some of which have also turned out to be stress-responsive proteins Li et al 2008;Gao et al 2009Gao et al , 2010Licausi et al 2011;Du et al 2013a).…”