Volume 11, Issue 4, Pages 515-517 (April 2018) Direct Convergence of Light and Auxin Signaling Pathways in Arabidopsis  Enamul Huq  Molecular Plant  Volume 11, Issue 4, Pages 515-517 (April 2018) DOI: 10.1016/j.molp.2018.02.002 Copyright © 2018 The Author Terms and Conditions

Figure 1 A Proposed Model for Direct Convergence of Light and Auxin Signaling Pathways. (A) In the dark, phytochromes are in an inactive Pr form located in the cytoplasm, while CRY1 is located both in the cytoplasm and nucleus. TIR1/AFBs form an SCF complex to induce degradation of AUX/IAA proteins. ARF transcription factors bind to DNA and promote auxin-induced gene expression and hypocotyl elongation. (B) Under white light with a high R:FR ratio, phyA is degraded while phyB is converted to the Pfr form, which migrates into the nucleus. Both phyB Pfr form and CRY1 interact with AUX/IAA proteins and stabilize them. Stable AUX/IAAs inhibit auxin-induced gene expression resulting in short hypocotyls. (C) Under shade and high-density planting conditions, a low R:FR ratio results in inactivation of phyB. TIR1/AFBs induce degradation of AUX/IAA proteins, resulting in auxin-induced gene expression and elongation of hypocotyls. (D) Under deep-canopy shade conditions, phyA is stabilized and is converted to an active Pfr form, which interacts with AUX/IAA proteins and stabilize them. Stable AUX/IAAs inhibit ARF activity and suppression of auxin-induced cell elongation. Thus, seedlings display short hypocotyls under deep-canopy shade conditions. The thickness of the arrows indicates transcription activity of the ARF proteins. The red circle indicates an auxin molecule. Molecular Plant 2018 11, 515-517DOI: (10.1016/j.molp.2018.02.002) Copyright © 2018 The Author Terms and Conditions