Strigolactone esterase D14

UniProtKB accession:  Q9SQR3

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UniProtKB description:  Involved in strigolactone signaling pathway (PubMed:22357928). Does not move long distances acropetally in the plant to regulate shoot branching and is rapidly degraded in the presence of strigolactones (PubMed:24610723). Functions downstream of strigolactone synthesis, as a component of hormone signaling and as an enzyme that participates in the conversion of strigolactones to the bioactive form (PubMed:22357928). Acts probably as a strigolactone receptor (PubMed:24610723). 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 (PubMed:22357928). Hydrolyzes methyl carlactonoate (MeCLA), but not carlactone (CL) or carlactonoic acid (CLA) (PubMed:25425668). Hydrolyzes the butenolide ring of strigolactones (PubMed:23381136). The initial nucleophilic attack causes an electron shift, followed by the addition of a water molecule, to lead to the release of the ABC ring product and the formation of a 'Ser-97'-stabilized open lactone intermediate (PubMed:23381136). Has no esterase activity for 4-nitrophenyl butyrate (PubMed:23381136). Binds and hydrolyzes the synthetic strigolactone analog GR24 in vitro. Forms a stable covalent complex with the D-ring of strigolactone, which is essential for hormone bioactivity. The D-ring is attached to His-247 of the catalytic triad. The hydrolysis of strigolactone into a covalently linked intermediate molecule initiates a conformational change of D14 to facilitate interaction with MAX2 and formation of the D14-MAX2-SKP1/ASK1 complex to trigger strigolactone signaling. This mechanism defines D14 as a non-canonical hormone receptor with dual functions to generate and sense the active form of strigolactone (PubMed:27479325).