title: Strigolactone regulates shoot development through a core signalling pathway.
abstract: Strigolactones are a recently identified class of hormone that regulate multiple aspects of plant development. The DWARF14 (D14) α/β fold protein has been identified as a strigolactone receptor, which can act through the SCFMAX2ubiquitin ligase, but the universality of this mechanism is not clear. Multiple proteins have been suggested as targets for strigolactone signalling, including both direct proteolytic targets of SCFMAX2, and downstream targets. However, the relevance and importance of these proteins to strigolactone signalling in many cases has not been fully established. Here we assess the contribution of these targets to strigolactone signalling in adult shoot developmental responses. We find that all examined strigolactone responses are regulated by SCFMAX2and D14, and not by other D14-like proteins. We further show that all examined strigolactone responses likely depend on degradation of SMXL proteins in the SMXL6 clade, and not on the other proposed proteolytic targets BES1 or DELLAs. Taken together, our results suggest that in the adult shoot, the dominant mode of strigolactone signalling is D14-initiated, MAX2-mediated degradation of SMXL6-related proteins. We confirm that the BRANCHED1 transcription factor and the PIN-FORMED1 auxin efflux carrier are plausible downstream targets of this pathway in the regulation of shoot branching, and show that BRC1 likely acts in parallel to PIN1.
authors: Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
authors: Tom
authors: http://orcid.org/0000-0003-1612-4019
authors: T
authors: Bennett
authors: Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
authors: Yueyang
authors: http://orcid.org/0000-0002-7427-1028
authors: Y
authors: Liang
authors: Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
authors: Madeleine
authors: http://orcid.org/0000-0002-8924-3943
authors: M
authors: Seale
authors: Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
authors: Sally
authors: http://orcid.org/0000-0002-5520-1331
authors: S
authors: Ward
authors: Department of Biology, University of York, York YO10 5DD, UK.
authors: Dörte
authors: D
authors: Müller
authors: Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK ol235@cam.ac.uk.|Department of Biology, University of York, York YO10 5DD, UK.
authors: Ottoline
authors: http://orcid.org/0000-0003-2161-3829
authors: O
authors: Leyser
keywords: Shoot branching; Signal transduction; Strigolactone