Location: Plant Physiology and Genetics ResearchTitle: CGI-58, a key regulator of lipid homeostasis and signaling in plants, also regulates polyamine metabolism) Author
Submitted to: Plant Signaling and Behavior
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/3/2014
Publication Date: 2/3/2014
Citation: Park, S., Keereetaweep, J., James, C.N., Gidda, S.K., Chapman, K., Mullen, R.T., Dyer, J.M. 2014. CGI-58, a key regulator of lipid homeostasis and signaling in plants, also regulates polyamine metabolism. Plant Signaling and Behavior. 9(1):e 27723. Interpretive Summary: Like all living organisms, plants have a myriad of metabolic pathways that must be fine tuned and regulated to allow the organism to grow and adapt to environmental changes. Two of the major metabolic pathways in plants include the production of lipids, which are essential components of all cellular membranes and serve as storage reserves in plant seeds, and polyamines, which are abundant compounds in plant cells that are critical for plant growth, development and stress responses. While a significant amount of information is known about the genes and enzymes involved in each specific area of metabolism, very little is know about how these different areas communicate with each other. In collaboration with scientists at the University of Guelph and the University of North Texas, scientists at the USDA-ARS lab in Maricopa, Arizona have identified a single protein in plants that regulates both lipid and polyamine metabolism. The protein functions by physically interacting with and stimulating the activity of two additional proteins, one of which is specific to lipid metabolism and the other of which is specific to polyamine metabolism. As such, this single protein serves as a higher order regulator that integrates and communicates between both metabolic pathways. This information will be of greatest interest to other scientists interested in understanding and manipulating lipid and/or polyamine metabolic pathways to improve plant growth and yields, particularly during biotic or abiotic stress response.
Technical Abstract: Comparative Gene Identification-58 (CGI-58) is an alpha/beta hydrolase-type protein that regulates lipid homeostasis and signaling in eukaryotes by interacting with and stimulating the activity of several different types of proteins, including a lipase in mammalian cells and a peroxisomal ABC transporter (PXA1) in plant cells. Here we show that plant CGI-58 also interacts with spermidine synthase 1 (SPDS1), an enzyme that plays a central role in polyamine metabolism by converting putrescine into spermidine. Analysis of polyamine contents in Arabidopsis thaliana plants revealed that spermidine levels were significantly reduced, and putrescine increased, in both cgi-58 and cgi-58/pxa1 mutant plants, relative to pxa1 mutant or wild-type plants. Evaluation of polyamine-related gene expression levels, however, revealed similar increases in transcript abundance in all mutants, including cgi-58, pxa1, and cgi-58/pxa1, in comparison to wild type. Taken together, the data support a model whereby CGI-58 and PXA1 contribute to the regulation of polyamine metabolism at the transcriptional level, perhaps through a shared lipid-signaling pathway, and that CGI-58 also acts independently of PXA1 to increase spermidine content at a post-transcriptional level, possibly through protein-protein interaction with SPDS1.