COMPUTATIONAL ANALYSES OF NATURAL VARIANTS FROM ARABIDOPSIS THALIANA PAIRED NLRS (RPS4:RRS1) LINKED TO THERMOTOLERANCE

Overview & Synopsis

Plant disease resistance can be negatively impacted by various abiotic stresses, the mechanisms of which are poorly understood. Lately, elevated temperature due to climate change has emerged as a key factor that impairs the function of certain nucleotide-binding leucine-rich repeat receptor (NLR) proteins essential for plant immunity.Among >100 tested ecotypes (accessions) of Arabidopsis thaliana, an accession from Sweden, Eden-1, retained immune response at elevated temperatures, while most others were susceptible. A major genetic determinant of the Eden-1 thermostable resistance phenotype is located within the RPS4/RRS1 locus, harbouring specific single-nucleotide polymorphisms. (SNPs). We aimed to investigate, with the aid of computational modelling, how specific RPS4:RRS1 polymorphisms among A. thaliana accessions play a role in their conformational stability. Consecutive structural modelling with AlphaFold 3 of inactive RPS4:RRS1 heterodimers revealed a distinct spatial arrangement among the modelled accessions comprising their leucine-rich repeats (LRR) and post-LRR domains, while Rosetta Energy calculations indicated Eden-1 possessed the most stable conformation. Gibbs free energy change (ΔΔG, kcal/mol) analysis showed a net destabilising effect of Eden-1 SNPs, while molecular dynamics simulations provided insights into the dynamic behaviour of complexes under near-physiological conditions. Together, these findings suggest Eden-1 polymorphisms drive conformational reorganisation that may underlie the thermotolerability of RPS4:RRS1 immune receptors. While offering valuable mechanistic insights, further structural studies of inactive and putative active complexes are required to fully elucidate the biological consequences of these SNPs.