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The gene encoding Arabidopsis acyl-CoA-binding protein 3 is pathogen inducible and subject to circadian regulation.

ABSTRACT: In Arabidopsis thaliana, acyl-CoA-binding protein 3 ( ACBP3), one of six ACBPs, is unique in terms of the C-terminal location of its acyl-CoA-binding domain. It promotes autophagy-mediated leaf senescence and confers resistance to Pseudomonas syringae pv. tomato DC3000. To understand the regulation of ACBP3, a 1.7 kb 5'-flanking region of ACBP3 and its deletion derivatives were characterized using β-glucuronidase (GUS) fusions. A 374 bp minimal fragment (-151/+223) could drive GUS expression while a 1698 bp fragment (-1475/+223) conferred maximal activity. Further, histochemical analysis on transgenic Arabidopsis harbouring the largest (1698 bp) ACBP3pro::GUS fusion displayed ubiquitous expression in floral organs and vegetative tissues (vascular bundles of leaves and stems), consistent with previous results showing that extracellularly localized ACBP3 functions in plant defence. A 160 bp region (-434/-274) induced expression in extended darkness and caused down-regulation in extended light. Electrophoretic mobility shift assay (EMSA) and DNase I footprinting assay showed that the DNA-binding with one finger box (Dof-box, -341/-338) interacted specifically with leaf nuclear proteins from dark-treated Arabidopsis, while GT-1 (-406/-401) binds both dark- and light-treated Arabidopsis, suggesting that Dof and GT-1 motifs are required to mediate circadian regulation of ACBP3. Moreover, GUS staining and fluorometric measurements revealed that a 109 bp region (-543/-434) was responsive to phytohormones and pathogens. An S-box of AT-rich sequence (-516/-512) was identified to bind nuclear proteins from pathogen-infected Arabidopsis leaves, providing the basis for pathogen-inducible regulation of ACBP3 expression. Thus, three cis-responsive elements (Dof, GT-1, and the S-box) in the 5'-flanking region of ACBP3 are proven functional in the regulation of ACBP3.

SUBMITTER: Zheng SX

PROVIDER: S-EPMC3350915 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:As plant seed oils provide animals with essential fatty acids (FAs), genes that regulate plant lipid metabolism have been used in genetic manipulation to improve dietary seed oil composition and benefit human health. Herein, the Arabidopsis thaliana cytosolic acyl-CoA-binding proteins (AtACBPs), AtACBP4, AtACBP5, and AtACBP6 were shown to play a role in determining seed oil content by analysis of atacbp (atacbp4, atacbp5, atacbp6, atacbp4atacbp5, atacbp4atacbp6, atacbp5atacbp6, and atacbp4atacbp5atacbp6) seed oil content in comparison with the Col-0 wild type (WT). Triacylglycerol (TAG) composition in electrospray ionization-mass spectrometer (ESI-MS) analysis on atacbp6 seed oil showed a reduction (-50%) of C58-TAGs in comparison with the WT. Investigations on fatty acid composition of atacbp mutants indicated that 18:2-FA accumulated in atacbp6 and 18:3-FA in atacbp4, both at the expense of 20:1-FA. As TAG composition can be modified by acyl editing through phosphatidylcholines (PC) and lysophosphatidylcholines (LPC), total PC and LPC content in atacbp6 mature seeds was determined and ESI-MS analysis revealed that LPC had increased (+300%) at the expense of PC. Among all the 14 tested PC species, all (34:1-, 34:2-, 34:3-, 34:4-, 34:5-, 34:6-, 36:2-, 36:3-, 36:5-, 36:6-, 38:2-, 38:3-, and 38:4-PCs) but 36:4-PC were lower in atacbp6 than the WT. In contrast, all LPC species (16:0-, 18:1-, 18:2-, 18:3-, and 20:1-LPC) examined were elevated in atacbp6. LPC abundance also increased in atacbp4atacbp5, but not atacbp4 and atacbp5. Interestingly, when LPC composition in atacbp4atacbp5 was compared with atacbp4 and atacbp5, significant differences were observed between atacbp4atacbp5 and each single mutant, implying that AtACBP4 and AtACBP5 play combinatory roles by affecting LPC (but not PC) biosynthesis. Furthermore, PC-related genes such as those encoding acyl-CoA:lysophphosphatidylcholine acyltransferase (LPCAT1) and phospholipase A2 alpha (PLA2α) were upregulated in atacbp6 developing seeds. A model on the role of AtACBP6 in modulating TAG through regulating LPCAT1 and PLA2α expression is proposed. Taken together, cytosolic AtACBPs appear to affect unsaturated TAG content and are good candidates for engineering oil crops to enhance seed oil composition.

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The gene encoding Arabidopsis acyl-CoA-binding protein 3 is pathogen inducible and subject to circadian regulation.

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