title: Arabidopsis acyl-CoA-binding protein ACBP6 localizes in the phloem and affects jasmonate composition.
abstract: Arabidopsis thaliana ACYL-COA-BINDING PROTEIN6 (AtACBP6) encodes a cytosolic 10-kDa AtACBP. It confers freezing tolerance in transgenic Arabidopsis, possibly by its interaction with lipids as indicated by the binding of acyl-CoA esters and phosphatidylcholine to recombinant AtACBP6. Herein, transgenic Arabidopsis transformed with an AtACBP6 promoter-driven β-glucuronidase (GUS) construct exhibited strong GUS activity in the vascular tissues. Immunoelectron microscopy using anti-AtACBP6 antibodies showed AtACBP6 localization in the phloem especially in the companion cells and sieve elements. Also, the presence of gold grains in the plasmodesmata indicated its potential role in systemic trafficking. The AtACBP6 protein, but not its mRNA, was found in phloem exudate of wild-type Arabidopsis. Fatty acid profiling using gas chromatography-mass spectrometry revealed an increase in the jasmonic acid (JA) precursor, 12-oxo-cis,cis-10,15-phytodienoic acid (cis-OPDA), and a reduction in JA and/or its derivatives in acbp6 phloem exudates in comparison to the wild type. Quantitative real-time PCR showed down-regulation of COMATOSE (CTS) in acbp6 rosettes suggesting that AtACBP6 affects CTS function. AtACBP6 appeared to affect the content of JA and/or its derivatives in the sieve tubes, which is consistent with its role in pathogen-defense and in its wound-inducibility of AtACBP6pro::GUS. Taken together, our results suggest the involvement of AtACBP6 in JA-biosynthesis in Arabidopsis phloem tissues.
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Zi-Wei
authors.initials: ZW
authors.lastname: Ye
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Shiu-Cheung
authors.initials: SC
authors.lastname: Lung
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Tai-Hua
authors.initials: TH
authors.lastname: Hu
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Qin-Fang
authors.initials: QF
authors.lastname: Chen
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Yung-Lee
authors.initials: YL
authors.lastname: Suen
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Mingfu
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Susanne
authors.initials: S
authors.lastname: Hoffmann-Benning
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada.
authors.forename: Edward
authors.initials: E
authors.lastname: Yeung
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China. mlchye@hku.hk.
authors.forename: Mee-Len
authors.initials: ML
authors.lastname: Chye
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism*; D054883:Oxylipins / Q000378:metabolism*; D052585:Phloem / Q000378:metabolism*
chemical_list: C532782:ACBP6 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D003517:Cyclopentanes; D054883:Oxylipins; C011006:jasmonic acid
keywords: Acyl-CoA-binding protein; Arabidopsis; Companion cell; OPDA; Phloem exudates; Sieve elements