5yz7
Crystal structure of OsD14 in complex with D-ring-opened 7'-carba-4BD
Structural highlights
FunctionD14_ORYSJ Involved in strigolactone signaling pathway. May function downstream of strigolactone synthesis, as a component of hormone signaling or as an enzyme that participates in the conversion of strigolactones to the bioactive form. Strigolactones are hormones that inhibit tillering and shoot branching through the MAX-dependent pathway, contribute to the regulation of shoot architectural response to phosphate-limiting conditions and function as rhizosphere signal that stimulates hyphal branching of arbuscular mycorrhizal fungi and trigger seed germination of root parasitic weeds.[1] [2] Publication Abstract from PubMedStrigolactones (SLs) are plant hormones that inhibit shoot branching and act as signals in communications with symbiotic fungi and parasitic weeds in the rhizosphere. SL signaling is mediated by DWARF14 (D14), which is an alpha/beta-hydrolase that cleaves SLs into an ABC tricyclic lactone and a butenolide group (i.e., D-ring). This cleavage reaction (hydrolysis and dissociation) is important for inducing the interaction between D14 and its target proteins, including D3 and D53. In this study, a hydrolysis-resistant SL analog was predicted to inhibit the activation of the D14 receptor, thereby disrupting the SL signaling pathway. To test this prediction, carba-SL compounds, in which the ether oxygen of the D-ring or the phenol ether oxygen of the SL agonist (GR24 or 4-bromo debranone) was replaced with a methylene group, were synthesized as novel D14 antagonists. Subsequent biochemical and physiological studies indicated that carba-SLs blocked the interaction between D14 and D53 by inhibiting D14 hydrolytic activity. They also suppressed the SL-induced inhibition of rice tiller outgrowths. Additionally, carba-SLs antagonized the SL response in a Striga parasitic weed species. Structural analyses revealed that the D-ring of 7'-carba-4BD was hydrolyzed by D14 but did not dissociate from the 4BD skeleton. Thus, 7'-carba-4BD functioned as an antagonist rather than an agonist. Thus, the hydrolysis of the D-ring of SLs may be insufficient for activating the receptor. This study provides data relevant to designing SL receptor antagonists. Rationally Designed Strigolactone Analogs as Antagonists of the D14 Receptor.,Takeuchi J, Jiang K, Hirabayashi K, Imamura Y, Wu Y, Xu Y, Miyakawa T, Nakamura H, Tanokura M, Asami T Plant Cell Physiol. 2018 May 2. pii: 4990988. doi: 10.1093/pcp/pcy087. PMID:29727000[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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