Strigolactones: Destruction-Dependent Perception?

Abstract

Strigolactones control many aspects of plant growth and development, but the active form(s) of strigolactones and their mode of action at the molecular level are unknown. A new study provides evidence that an α/β-fold protein plays a central multifunctional role in strigolactone metabolism, perception and signalling.

Action of Strigolactones in Plants

“…Moreover, overexpression of D14 could not complement the dwarf or high-tillering phenotype of d3, implying that D3 may act downstream of D14, which is consistent with the idea that D14 is involved in the first step of the SL perception [37]. It is possible that an SL derivative produced by D14 may act as a true signal for the SCF D3 complex to trigger the polyubiquitination and degradation of target proteins in SL signaling [49]. However, the possibility cannot be ruled out that D14 may be involved in the biosynthesis or modification of an unidentified SL derivative, which is a biologically active compound in the inhibition of shoot branching.…”

“…Crystallography studies further suggested that the hydrolysis product of GR24 was covalently attached to the active-site Ser in the catalytic triad [47,48]. Given that the breakdown of GR24 by DAD2 or D14 is slow and the concentration of the binding of GR24 with D14 is quite high [21,37], it has been suggested that a very slow metabolism might be necessary for the perception of SL signal, which is distinct between D14 and GID1 that shows no hydrolase activity [21,37,49].…”

DWARF 53 acts as a repressor of strigolactone signalling in rice

“…D14 encodes a member of α/β-hydrolase fold family protein and is proposed to be a candidate SL receptor 18–20,27,28 , and D3 encodes a Leu-rich repeat F-box protein and participates in SL perception 14 . D14 has a canonical α/β-hydrolase fold structure and disruption of the hydrolase activity of D14 homologue DAD2 in petunia abolishes SL-induced interaction between DAD2 and PhMAX2A, one of the D3 homologues in petunia, indicating that SL-mediated interaction of DAD2 with PhMAX2A may trigger the SCF E3 ligase to target an unknown substrate for ubiquitination and degradation 24,27–29 . Previous study identified a dominant tillering dwarf mutant dwarf 53 ( d53 ) 30 , and the D53 locus was primarily mapped to the short arm of chromosome 11 (ref 31…”

Strigolactone Signaling in Arabidopsis Regulates Shoot Development by Targeting D53-Like SMXL Repressor Proteins for Ubiquitination and Degradation

“…The crystal structures of D14 proteins from rice, petunia (DAD2), and Arabidopsis ( D14) revealed an a/b-fold hydrolase with a large internal cavity capable of accommodating SLs and containing a canonical catalytic triad (Hamiaux et al, 2012;Bythell-Douglas et al, 2013;Kagiyama et al, 2013;Zhao et al, 2013Zhao et al, , 2015. The catalytic triad of DAD2/D14 is required for hydrolysis of SLs, which can trigger interaction between DAD2 and MAX2 in petunia and interaction between D14 and D3 in rice, as part of SCF-mediated signal transduction (Hamiaux et al, 2012;Smith and Waters, 2012;Jiang et al, 2013;Zhou et al, 2013;Zhao et al, 2014Zhao et al, , 2015. Furthermore, the crystal structure of D14 incubated with rac-GR24 revealed a derivative of the butenolide covalently attached to the active-site Ser residue .…”