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Plant Physiology Preview Published on March 25, 2009; 10.1104/pp.109.137745
Received February 25, 2009 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
Department of Plant Biotechnology and Agricultural Plant Stress Research Center; Department of Wood Science and Technology; 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; School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea; Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea * Corresponding author; email: mcsuh{at}chonnam.ac.kr.
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 (LTP) are involved in cuticular lipid transport, the in planta evidence is still not clear. In this study, a glycosylphosphatidylinositol (GPI)-anchored LTP (LTPG1) showing higher expression in epidermal peels of stems than in stems was identified from an Arabidopsis genome-wide microarray analysis. The expression of LTPG1 gene was observed in various tissues including the epidermis, stem cortex, vascular bundles, mesophyll cells, root tips, pollen, and early developing seeds. The 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. The largest reduction (10 mass%) in the ltpg1 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 the ltpg1 showed more diffused cuticular layer structure and 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.
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