Mechanistic basis for enhanced strigolactone sensitivity in KAI2 triple mutant

Area of Science:

• Molecular biology
• Plant science
• Biochemistry

Background:

• Striga hermonthica is a devastating parasitic weed impacting global crop yields.
• Parasitic weeds exploit plant hormones called strigolactones (SLs) for proliferation.
• The SL receptor in Striga (ShHTL7) is similar to plant KAI2 receptors, which typically have low SL sensitivity.

Purpose of the Study:

• To investigate the molecular mechanisms by which point mutations confer SL sensitivity to the Arabidopsis thaliana KAI2 (AtKAI2) receptor.
• To understand how these mutations affect SL binding affinity and kinetics at a molecular level.

Main Methods:

• All-atom, long-timescale molecular dynamics simulations were employed.
• Wild-type AtKAI2 and a mutant variant (Var64) were analyzed.
• Key molecular interactions and conformational changes related to SL binding were assessed.

Main Results:

• Mutations were found to stabilize SL binding by approximately 2 kcal/mol.
• The average binding pocket volume doubled in the mutant receptor.
• The mutant receptor showed increased SL binding rates (10-fold increase) and reduced conformational dependence for binding.

Conclusions:

• Specific point mutations significantly enhance the strigolactone sensitivity of AtKAI2 receptors.
• These molecular changes provide a basis for understanding enhanced parasitic weed adaptation.
• Findings suggest strategies for engineering improved SL receptor functionality in crops to enhance resistance.