In Silico Analysis of Rpp1 Locus-Derived NB-ARC-LRR Domains Reveals Insights into Rust Resistance in Soybean

Soybean rust poses significant economic challenges to soybean producers, resulting in decreased seed size, weight, oil content, and overall crop yield. This study aimed to comprehensively characterize the rust resistance locus Rpp1 identified in soybean genotype EC 241780 and its associated genes within the soybean genome. Our investigation revealed distinctive features of three genes (Glyma18G281700, Glyma18G281600, and Glyma18G281500) located within the Rpp1 locus on chromosome 18. Phylogenetic and domain analyses confirmed the presence of the ULP1 domain in these genes, while motif analysis identified unique patterns exclusive to them. Notably, these genes possessed exclusive isoleucine and glutamic acid residues at positions 836 and 904, along with an unusual expansion of 11 glutamic acid residues at position 861. Expression-data showed significantly higher expression levels of Glyma18G281700 and Glyma18G281600 during leaf trifoliate stages I and II, suggesting their active involvement under adverse conditions. Protein structure analysis revealed that Glyma18G281500 exhibited distinct characteristics compared to the other two genes and displayed a more stable protein structure. This observation may indicate a distinct functional role for Glyma18G281500. In conclusion, our findings suggest that the genes within the Rpp1 locus may contribute to rust resistance, particularly against specific rust races, due to their unique characteristics associated with the ULP1 domain.