ARS | Publication request: TEMPERATURE-SENSITIVE, POST-TRANSLATIONAL REGULATION OF PLANT OMEGA-3 FATTY ACID DESATURASES IS MEDIATED BY THE ER-ASSOCIATED DEGRADATION PATHWAY

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2010
Publication Date: April 24, 2010
Citation: Zhang, D., Quin, J.B., Bourassa, L., Foss, S., Shockey, J.M., Gidda, S.K., Chapman, K.D., Mullen, R.T., and Dyer, J.M. (2010). Temperature-sensitive, post-translational regulation of plant omega-3 fatty acid desaturases is mediated by the ER-associated degradation pathway. Annual Meeting of the American Society of Biochemistry and Molecular Biology, April 24 - 28, 2010, Anaheim, CA.

Technical Abstract: In plants, the endoplasmic reticulum (ER)-localized omega-3 fatty acid desaturases (Fad3s) increase the production of polyunsaturated fatty acids at cooler temperatures, but the FAD3 genes themselves are typically not upregulated during this adaptive response. Here, we expressed two closely related plant FAD3 genes in yeast cells and found that their enzymes produced significantly different amounts of omega-3 fatty acids. Moreover, protein amounts were determined primarily by differences in rates of protein turnover, rather than mRNA levels, indicating that the Fad3 proteins are differentially regulated at the post-translational level. Domain-swapping and mutagenesis experiments revealed that each Fad3 protein contained a degradation signal in their N-terminal region and that the charge density of a PEST-like sequence within this region was largely responsible for the differences in their protein half-lives. The half-lives of both Fad3 proteins were increased at cooler temperatures and their protein degradation required Cdc48 adaptor proteins, Doa1 and Shp1, as well as proteasomal activity. Collectively, these findings indicate that the steady-state amount of Fad3 proteins (and thus Fad3 activity) is modulated in response to temperature through a combination of cis-acting degradation signals and specific components of the ER-associated degradation pathway.