Location: Plant Physiology and Genetics ResearchTitle: The alpha/beta hydrolase CGI-58 and peroxisomal transport protein PXA1 coregulate lipid homeostasis and signaling in Arabidopsis) Author
Submitted to: The Plant Cell
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/23/2013
Publication Date: 5/10/2013
Publication URL: http://handle.nal.usda.gov/10113/57031
Citation: Park, S., Gidda, S.K., James, C.N., Horn, P.J., Khuu, N., Seay, D.C., Keereetaweep, J., Chapman, K.D., Mullen, R.T., and Dyer, J.M. 2013. The alpha/beta hydrolase CGI-58 and peroxisomal transport protein PXA1 coregulate lipid homeostasis and signaling in Arabidopsis. Plant Cell. 25:1726-1739. Interpretive Summary: Plants serve as natural, renewable sources of both food and fuel, and in recent years there has been increasing demand for plant oils as a feedstock for “biodiesel” production. Current agricultural practices and yields of oilseed crops, however, are unable to meet the burgeoning oil demand, and novel approaches for producing higher amounts of oil in plants are greatly needed. In collaboration with scientists at the University of Guelph, University of North Texas, and Del Mar College, ARS scientists are examining the possibility of producing oil in the “vegetative” parts of plants (e.g., leaves and stems), in addition to seeds. The rationale is that the biomass of vegetative plant parts is significantly greater than that of seeds (the normal source of plant oil), and thus, increasing oil in vegetative tissues could significantly increase the amount of oil recovered from a given area of land. This manuscript provides fundamental insight to the mechanisms that plants use to regulate the amount of oil in their leaves and stems. In essence, the work describes a “thermostat”-like mechanism that helps fine tune the amounts of oil present in plant leaves, and also how the “thermostat” can be turned up to increase the amount of oils in plants. The research has immediate implications for scientists interested in understanding fundamental aspects of oil production, storage and mobilization in plants, and also may shed light on a variety of important lipid disorders (such as Chanarin-Dorfman syndrome, Zellweger syndrome, and adrenoleukodystrophy) in humans.
Technical Abstract: COMPARATIVE GENE IDENTIFICATION-58 (CGI-58) is a key regulator of lipid metabolism and signaling in mammals, but its underlying mechanisms are unclear. Disruption of CGI-58 in either mammals or plants results in a significant increase in triacylglycerol (TAG), suggesting that CGI-58 activity is evolutionarily conserved. However, plants lack proteins that are important for CGI-58 activity in mammals. Here, we demonstrate that CGI-58 functions by interacting with the PEROXISOMAL ABC-TRANSPORTER1 (PXA1), a protein that transports a variety of substrates into peroxisomes for their subsequent metabolism by beta-oxidation, including fatty acids and lipophilic hormone precursors of the jasmonate and auxin biosynthetic pathways. We show also that mutant cgi-58 plants display changes in jasmonate biosynthesis, auxin signaling, and lipid metabolism consistent with reduced PXA1 activity in planta and that, based on the double mutant cgi-58/pxa1, PXA1 is epistatic to CGI-58 in all of these processes. However, CGI-58 was not required for the PXA1-dependent breakdown of TAG in germinated seeds. Collectively, the results reveal that CGI-58 positively regulates many aspects of PXA1 activity in plants and that these two proteins function to coregulate lipid metabolism and signaling, particularly in nonseed vegetative tissues. Similarities and differences of CGI-58 activity in plants versus animals are discussed.