Seeds employ sensory systems that assess various environmental cues over time to maximize the successful transition from embryo to seedling. Here we show that the Arabidopsis F-BOX protein COLD TEMPERATURE-GERMINATING (CTG)-10, identified by activation tagging, is a positive regulator of this process. When overexpressed (OE), CTG10 hastens aspects of seed germination. CTG10 is expressed predominantly in the hypocotyl, and the protein is localized to the nucleus. CTG10 interacts with PHYTOCHROME-INTERACTING FACTOR 1 (PIF1) and helps regulate its abundance in planta. CTG10-OE accelerates the loss of PIF1 in light, increasing germination efficiency, while PIF1-OE lines fail to complete germination in darkness, which is reversed by concurrent CTG10-OE. Double-mutant (pif1 ctg10) lines demonstrated that PIF1 is epistatic to CTG10. Both CTG10 and PIF1 amounts decline during seed germination in the light but reaccumulate in the dark. PIF1 in turn down-regulates CTG10 transcription, suggesting a feedback loop of CTG10/PIF1 control. The genetic, physiological, and biochemical evidence, when taken together, leads us to propose that PIF1 and CTG10 coexist, and even accumulate, in the nucleus in darkness, but that, following illumination, CTG10 assists in reducing PIF1 amounts, thus promoting the completion of seed germination and subsequent seedling development.
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Funding support included a pilot project and research grant from the Kentucky Tobacco Research and Development Center at the University of Kentucky (to A.B.D.), National Science Foundation Division of Integrative Organismal Systems Collaborative Research Grant 0849230 (to A.B.D. and E.H.), NIH Grant 1R01 GM-114297 (to E.H.), National Science Foundation Supplement 0849230 (to T.D.L. and A.B.D.), an American Society of Plant Biologists Summer Undergraduate Research Fellowship (to T.D.L.), US Department of Agriculture–National Institute of Food and Agriculture Seed Grant 2011-04375 (to A.B.D.), and Kentucky Agricultural Experiment Station Grant KY011038 (to A.B.D. and L.M.A.D.).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1711919115/-/DCSupplemental.
Majee, Manoj; Kumar, Santosh; Kathare, Praveen Kumar; Wu, Shuiqin; Gingerich, Derek; Nayak, Nihar R.; Salaita, Louai; Dinkins, Randy; Martin, Kathleen; Goodin, Michael M.; Dirk, Lynnette M. A.; Lloyd, Taylor D.; Zhu, Ling; Chappell, Joseph; Hunt, Arthur G.; Vierstra, Richard; Huq, Enamul; and Downie, A. Bruce, "KELCH F-BOX Protein Positively Influences Arabidopsis Seed Germination by Targeting PHYTOCHROME-INTERACTING FACTOR1" (2018). Horticulture Faculty Publications. 32.