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United States Department of Agriculture

Agricultural Research Service

Research Project: Commercialization of New Industrial Crop Germplasm and Cropping Systems

Location: Plant Physiology and Genetics Research

Title: Cgi-58 Regulates Triacylglycerol Homeostasis and Lipid Signaling Pathways in Plants Through Interaction with the Peroxisomal Transport Protein Pxa1.

Authors
item Dyer, John
item Gidda, S -
item James, C -
item Khuu, N -
item Seay, D -
item Keereetaweep, J -
item Chapman, K -
item Mullen, R -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 2, 2012
Publication Date: N/A

Technical Abstract: Mutation of the Comparative Gene Identification-58 (CGI-58) gene in humans causes Chanarin-Dorfman syndrome, a rare genetic disorder characterized by an increase in triacylglycerol (TAG) and lipid droplet (LD) contents in non-lipid-storing cell types. Interestingly, disruption of the CGI-58 homologue in Arabidopsis causes a similar accumulation of TAG and LDs in non-lipid storing tissues (e.g., leaves and stems), suggesting that the molecular mechanism(s) underpinning CGI-58 activity might be conserved in plants and animals. Key proteins known to be important for modulating the activity of CGI-58 in mammals through protein-protein interaction, however, are absent in plants. To elucidate the function of CGI-58 in plants, we used Arabidopsis CGI-58 as bait in a yeast two-hybrid screen and identified PXA1 as an interacting protein. PXA1 is a peroxisomal membrane protein that transports both fatty acids and lipophilic hormones (e.g., 12-oxophytodienoic acid [OPDA] and indole-3-butyric acid [IBA]) into the peroxisome for subsequent breakdown or metabolic conversion to jasmonic acid (JA) and indole-3-acetic acid (IAA), respectively. Other experiments have shown that disruption of PXA1, like CGI-58, results in the abnormal accumulation of TAG and lipid droplets in vegetative cells types, suggesting that CGI-58 and PXA1 are functionally related. In support of this premise, cgi-58 mutant plants showed elevated accumulation of OPDA and reduced amounts of JA in response to plant wounding, similar to (but less severe than) pxa1 mutants. In addition, cgi-58 mutant plants were resistant to the effects of IBA (the peroxisomal precursor) in root elongation assays, but sensitive to IAA (the peroxisomal product). Unlike pxa1 mutants, however, cgi-58 mutant seeds can germinate and undergo seedling establish in the absence of exogenously provided sucrose. Collectively, these results indicate that CGI-58 and PXA1 function cooperatively in the regulation of fatty acid (and thus TAG) homeostasis in vegetative tissues, and also regulate a variety of lipid signaling pathways. Implications for the metabolic engineering of plants for enhanced oil production, as well as new insights to lipid metabolic disorders in humans, will be discussed.

Last Modified: 7/28/2014
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