Journal
PLANT CELL
Volume 29, Issue 4, Pages 871-889Publisher
OXFORD UNIV PRESS INC
DOI: 10.1105/tpc.17.00019
Keywords
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Funding
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, through the Physical Biosciences program of the Chemical Sciences, Geosciences, and Biosciences Division [DE-SC0012704]
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WRINKLED1 (WRI1), a member of the APETALA2 (AP2) class of transcription factors, positively regulates glycolysis and lipid biosynthesis in Arabidopsis thaliana. Here, we identify mechanistic links between KIN10, the major SUCROSE NON-FERMENTATION1-RELATED KINASE1 involved in sugar/energy homeostasis, and the posttranslational regulation of WRI1. Transient expression of WRI1 with OLEOSIN1 in Nicotiana benthamiana stimulates triacylglycerol accumulation, but their coexpression with KIN10 abrogates this effect by inducing proteasomal degradation of WRI1. While WRI1 lacks canonical KIN10 target sequences, we demonstrated direct KIN10-dependent phosphorylation of WRI1 using purified Escherichia coliexpressed components. The resulting phosphorylated WRI1 was more rapidly degraded than native WRI1 in cell-free degradation assays. WRI1 phosphorylation was localized to two variants of the canonical KIN10 recognition sequence, one in each of its two AP2 DNA binding domains. Conversion of the phosphorylation sites at Thr-70 and Ser-166 to Ala resulted in a loss of KIN10-dependent phosphorylation, and when coexpressed with KIN10 the WRI1 double mutant accumulated to 2- to 3-fold higher levels than native WRI1. KIN10-dependent degradation of WRI1 provides a homeostatic mechanism that favors lipid biosynthesis when intracellular sugar levels are elevated and KIN10 is inhibited; conversely, glycolysis and lipid biosynthesis are curtailed as sugar levels decrease and KIN10 regains activity.
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