Molecular Mechanism of Brassinosteroid Perception by the Plant Growth Receptor BRI1

Aldukhi, Faisal; Deb, Aniket; Zhao, Chuankai; Moffett, Alexander S.; Shukla, Diwakar

doi:10.1021/acs.jpcb.9b09377

Cited by 22 publications

(23 citation statements)

References 74 publications

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“…This coupling of binding and hydrolysis makes it difficult to elucidate the effects of substrate binding on signaling independently of subsequent steps. A powerful method that can be used to characterize the strigolactone binding process is molecular dynamics (MD) simulations ( 20 , 21 , 22 , 23 , 24 , 25 , 26 ). When used with Markov state models (MSMs), simulations can provide detailed kinetic and thermodynamic information about ligand-binding processes at atomic-level resolution ( 27 , 28 , 29 , 30 , 31 , 32 ).…”

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confidence: 99%

Role of substrate recognition in modulating strigolactone receptor selectivity in witchweed

Chen

White

Nelson

et al. 2021

Journal of Biological Chemistry

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Witchweed, or Striga hermonthica , is a parasitic weed that destroys billions of dollars' worth of crops globally every year. Its germination is stimulated by strigolactones exuded by its host plants. Despite high sequence, structure, and ligand-binding site conservation across different plant species, one strigolactone receptor in witchweed, Sh HTL7, uniquely exhibits a picomolar EC50 for downstream signaling. Previous biochemical and structural analyses have hypothesized that this unique ligand sensitivity can be attributed to a large binding pocket volume in Sh HTL7 resulting in enhanced ability to bind substrates, but additional structural details of the substrate-binding process would help explain its role in modulating the ligand selectivity. Using long-timescale molecular dynamics simulations, we demonstrate that mutations at the entrance of the binding pocket facilitate a more direct ligand-binding pathway to Sh HTL7, whereas hydrophobicity at the binding pocket entrance results in a stable “anchored” state. We also demonstrate that several residues on the D-loop of At D14 stabilize catalytically inactive conformations. Finally, we show that strigolactone selectivity is not modulated by binding pocket volume. Our results indicate that while ligand binding is not the sole modulator of strigolactone receptor selectivity, it is a significant contributing factor. These results can be used to inform the design of selective antagonists for strigolactone receptors in witchweed.

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confidence: 99%

Role of substrate recognition in modulating strigolactone receptor selectivity in witchweed

Chen

White

Nelson

et al. 2021

Journal of Biological Chemistry

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“…Finally, recent work from our group has tried to provide a comprehensive structural and dynamic view of plant hormone signaling for ABA 33 , Brassinosteroid 40,56,57 and Strigolactone 58 hormone receptors in plants. These physical insights into the structural, dynamic and energetic basis of the activation of hormone receptors in Arabidopsis thaliana, which are challenging to obtain with experimental approaches.…”

Section: Discussionmentioning

confidence: 99%

Molecular Basis of the Activation and Dissociation of Dimeric PYL2 Receptor in Abscisic Acid Signaling

Zhao

Shukla

2019

Preprint

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Phytohormone abscisic acid (ABA) is essential for plant responses to biotic and abiotic stresses. Dimeric receptors are a class of ABA receptors that are important for various ABA responses. While extensive experimental and computational studies have investigated these receptors, it remains not fully understood how ABA leads to their activation and dissociation for interaction with downstream phosphatase. It also remains unknown how networks of water molecules present in the binding site affect ABA perception despite its critical role in protein-ligand binding. Here, we study the activation and the homodimeric association processes of PYL2 receptor as well as its heterodimeric association with the phosphatase HAB1 using molecular dynamics simulations. Free energy landscapes from ∼223 µs simulations show that dimerization substantially constrains PYL2 conformational plasticity and stabilizes inactive state, resulting in lower ABA affinity. Using hydration site analysis to characterize receptor solvation thermodynamics, we show that the displacement and reorganization of water molecules upon ABA binding contribute to binding affinity via gain of entropy and enthalpy, respectively. The penalty for expelling water molecules into the bulk causes the free energy barrier to binding (∼4-5 kcal/mol). Finally, we establish the thermodynamic model for competitive binding between homodimeric PYL2 association and heterodimeric PYL2-HAB1 association in the absence and presence of ABA. Our results suggest that the binding of ABA destabilizes PYL2 complex and further stabilizes PYL2-HAB1 association, thereby promoting PYL2 dissociation. Overall, this study explains several key aspects on activation of dimeric ABA receptors, which provide new avenues for selective regulation of these receptors.

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“…This study used 24-epicastasterone (ECS), which is a precursor of castasterone, an end product of BR biosynthesis pathway in rice [ 35 ], and has been shown to be biologically active but less so than brassinolide [ 36 ]. ECS (Yuanye Biology, Shanghai, China), was dissolved in 80% ethanol.…”

Section: Methodsmentioning

confidence: 99%

Supraoptimal Brassinosteroid Levels Inhibit Root Growth by Reducing Root Meristem and Cell Elongation in Rice

Jantapo

Wimonchaijit

Wang

et al. 2021

Plants

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Root growth depends on cell proliferation and cell elongation at the root meristem, which are controlled by plant hormones and nutrient availability. As a foraging strategy, rice (Oryza sativa L.) grows longer roots when nitrogen (N) is scarce. However, how the plant steroid hormone brassinosteroid (BR) regulates rice root meristem development and responses to N deficiency remains unclear. Here, we show that BR has a negative effect on meristem size and a dose-dependent effect on cell elongation in roots of rice seedlings treated with exogenous BR (24-epicastasterone, ECS) and the BR biosynthesis inhibitor propiconazole (PPZ). A genome-wide transcriptome analysis identified 4110 and 3076 differentially expressed genes in response to ECS and PPZ treatments, respectively. The gene ontology (GO) analysis shows that terms related to cell proliferation and cell elongation were enriched among the ECS-repressed genes. Furthermore, microscopic analysis of ECS- and PPZ-treated roots grown under N-sufficient and N-deficient conditions demonstrates that exogenous BR or PPZ application could not enhance N deficiency-mediated root elongation promotion as the treatments could not promote root meristem size and cell elongation simultaneously. Our study demonstrates that optimal levels of BR in the rice root meristem are crucial for optimal root growth and the foraging response to N deficiency.

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Molecular Mechanism of Brassinosteroid Perception by the Plant Growth Receptor BRI1

Cited by 22 publications

References 74 publications

Role of substrate recognition in modulating strigolactone receptor selectivity in witchweed

Role of substrate recognition in modulating strigolactone receptor selectivity in witchweed

Molecular Basis of the Activation and Dissociation of Dimeric PYL2 Receptor in Abscisic Acid Signaling

Supraoptimal Brassinosteroid Levels Inhibit Root Growth by Reducing Root Meristem and Cell Elongation in Rice

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