Abstract
ACBP3 is one of six Arabidopsis (Arabidopsis thaliana) genes, designated ACBP1 to ACBP6, that encode acyl-coenzyme A (CoA)-binding proteins (ACBPs). These ACBPs bind long-chain acyl-CoA esters and phospholipids and are involved in diverse cellular functions, including acyl-CoA homeostasis, development, and stress tolerance. Recombinant ACBP3 binds polyunsaturated acyl-CoA esters and phospholipids in vitro. Here, we show that ACBP3 plays a role in the plant defense response to the bacterial pathogen Pseudomonas syringae pv tomato DC3000. ACBP3 mRNA was up-regulated upon pathogen infection and treatments using pathogen elicitors and defense-related phytohormones. Transgenic Arabidopsis ACBP3 overexpressors (ACBP3-OEs) showed constitutive expression of pathogenesis-related genes (PR1, PR2, and PR5), cell death, and hydrogen peroxide accumulation in leaves. Consequently, ACBP3-OEs displayed enhanced resistance to the bacterial pathogen P. syringae DC3000. In contrast, the acbp3 T-DNA insertional mutant was more susceptible and exhibited lower PR gene transcript levels upon infection. Using the ACBP3 OE-1 line in combination with nonexpressor of PR genes1 (npr1-5) or coronatine-insensitive1 (coi1-2), we concluded that the enhanced PR gene expression and P. syringae DC3000 resistance in the ACBP3-OEs are dependent on the NPR1-mediated, but not the COI1-mediated, signaling pathway. Given that ACBP3-OEs showed greater susceptibility to infection by the necrotrophic fungus Botrytis cinerea while the acbp3 mutant was less susceptible, we suggest that ACBP3 plays a role in the plant defense response against biotrophic pathogens that is distinct from necrotrophic pathogens. ACBP3 function in plant defense was supported further by bioinformatics data showing up-regulation of many biotic and abiotic stress-related genes in ACBP3 OE-1 in comparison with the wild type.
Highlights
ACBP3 is one of six Arabidopsis (Arabidopsis thaliana) genes, designated ACBP1 to ACBP6, that encode acyl-coenzyme A (CoA)binding proteins (ACBPs)
Our observations of disrupted autophagosome formation accompanied by an enhanced degradation of the GFP-ATG8e protein, a translational fusion of GFP to the autophagy protein 8e (ATG8e), in the combined ACBP3 OE-1 GFP-ATG8e line during starvation have linked ACBP3 function to the regulation of ATG8-PE complex formation and autophagy-mediated leaf senescence (Xiao et al, 2010)
These findings indicate that ACBP3 expression is up-regulated upon pathogen infection and treatment with the phytohormones ACC, methyl jasmonate (MeJA), and
Summary
ACBP3 is one of six Arabidopsis (Arabidopsis thaliana) genes, designated ACBP1 to ACBP6, that encode acyl-coenzyme A (CoA)binding proteins (ACBPs). The acyl-CoA-binding proteins (ACBPs) are conserved at the ACB domain (Xiao and Chye, 2009, 2011) They have been identified from various organisms, including plants, yeast, Drosophila, and mammals, and implicated in diverse functions such as acyl-CoA and/ or phospholipid metabolism, acyl-CoA trafficking and homeostasis, protection of acyl lipids from cytosolic enzymes, growth, development, and stress tolerance (Knudsen et al, 2000; Faergeman and Knudsen, 2002; Xiao and Chye, 2009, 2011; Yurchenko et al, 2009; Fan et al, 2010; Yurchenko and Weselake, 2011). Alterations in ACBP3 expression in ACBP3-OE and acbp mutant lines were found to affect responses to bacterial pathogen infection, suggesting a role for ACBP3 in plant defense that was investigated further using SA signaling (nonexpressor of PR genes1 [npr and npr1-5]) and jasmonic acid (JA) signaling (coronatine-insensitive1 [coi1-2]) mutants
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