Structure-based characterization of RLKomes reveals lineage-specific families in oomycetes

Abstract Receptor-like kinases (RLKs) are a large family of transmembrane receptors that play central roles in signal perception and transduction in plants. However, their distribution and evolution in oomycetes, which belong to the Stramenopiles lineage, remain largely unexplored. Here, we conducted a systematic, proteome-wide survey of RLKomes across 233 stramenopile species, including 179 oomycetes and 54 other stramenopiles. In total, we identified 11,357 RLKs (10,867 in oomycetes), which are mainly clustered into six core families, with the LRR family accounting for the largest proportion. The remaining five correspond to distinct RLK families present in oomycetes, including the elicitin family, the EGF domain-containing family, and three functionally uncharacterized families. Collectively, our results systematically delineate the distribution patterns and structural diversity of the RLK superfamily in oomycetes. Furthermore, the specialized oomycete RLK database established in this study provides a foundational resource for investigating the evolutionary dynamics and functional mechanisms of these critical signaling molecules.