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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Disruption of Glycosylphosphatidylinositol-Anchored Lipid Transfer Protein Gene Altered Cuticular Lipid Composition, Increased Plastoglobules, and Enhanced Susceptibility to Infection by the Fungal Pathogen Alternaria brassicicola^1,[W]

Department of Plant Biotechnology and Agricultural Plant Stress Research Center (S.B.L., Y.S.G., M.C.S.) and Department of Wood Science and Technology (H.-J.B.), College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500–757, Republic of Korea; Department of Biological Sciences, Inha University, Incheon 402–751, Republic of Korea (J.H.P., S.H.C.); School of Life Sciences and Biotechnology, Korea University, Seoul 136–701, Republic of Korea (H.J.C., D.S.L., O.K.P.); and Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790–784, Republic of Korea (I.H.)

All aerial parts of vascular plants are covered with cuticular waxes, which are synthesized by extensive export of intracellular lipids from epidermal cells to the surface. Although it has been suggested that plant lipid transfer proteins (LTPs) are involved in cuticular lipid transport, the in planta evidence is still not clear. In this study, a glycosylphosphatidylinositol-anchored LTP (LTPG1) showing higher expression in epidermal peels of stems than in stems was identified from an Arabidopsis (Arabidopsis thaliana) genome-wide microarray analysis. The expression of LTPG1 was observed in various tissues, including the epidermis, stem cortex, vascular bundles, mesophyll cells, root tips, pollen, and early-developing seeds. LTPG1 was found to be localized in the plasma membrane. Disruption of the LTPG1 gene caused alterations of cuticular lipid composition, but no significant changes on total wax and cutin monomer loads were seen. The largest reduction (10 mass %) in the ltpg1 mutant was observed in the C29 alkane, which is the major component of cuticular waxes in the stems and siliques. The reduced content was overcome by increases of the C29 secondary alcohols and C29 ketone wax loads. The ultrastructure analysis of ltpg1 showed a more diffuse cuticular layer structure, protrusions of the cytoplasm into the vacuole in the epidermis, and an increase of plastoglobules in the stem cortex and leaf mesophyll cells. Furthermore, the ltpg1 mutant was more susceptible to infection by the fungus Alternaria brassicicola than the wild type. Taken together, these results indicated that LTPG1 contributed either directly or indirectly to cuticular lipid accumulation.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Mi Chung Suh (mcsuh{at}chonnam.ac.kr).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.137745

^* Corresponding author; e-mail mcsuh{at}chonnam.ac.kr.

Received February 25, 2009; accepted March 19, 2009; published March 25, 2009.

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