Mechanistic Basis for Enhanced Strigolactone Sensitivity in KAI2 Triple Mutant

Area of Science:

• Plant Biology
• Biochemistry
• Molecular Modeling

Background:

• Striga hermonthica is a parasitic weed causing significant crop losses.
• Striga's proliferation is linked to its efficient metabolism of strigolactones (SLs).
• The SL receptor ShHTL7 shares similarity with the karrikin receptor KAI2, which typically has low SL sensitivity.

Purpose of the Study:

• To investigate the molecular mechanisms behind increased SL sensitivity in KAI2 mutants.
• To determine how specific mutations affect the binding of SLs to the KAI2 receptor.

Main Methods:

• All-atom, long-timescale molecular dynamics simulations were employed.
• Wild-type AtKAI2 and an SL-sensitive mutant (Var64) were analyzed.
• The effects of mutations on receptor-ligand interactions and pocket dynamics were assessed.

Main Results:

• Mutations were found to stabilize SL binding by approximately 2 kcal/mol.
• The average pocket volume of the SL-sensitive mutant doubled compared to the wild-type.
• Mutations increased the rate of SL binding by tenfold and reduced dependence on specific pocket conformations.

Conclusions:

• The identified mutations confer enhanced SL sensitivity to AtKAI2 by altering binding stability and pocket dynamics.
• These findings provide a molecular basis for understanding SL receptor function.
• The study suggests strategies for engineering improved SL receptor functionality in crops to enhance resistance against parasitic weeds.