ARGOS Genes in Cauliflower: Genome-Wide Identification and Functional Validation of BobARL2 Under Abiotic Stresses

The Auxin-Regulated Gene Involved in Organ Size (ARGOS) proteins have crucial regulatory effects on organ size and responses to environmental stresses. Despite their importance, <i>Brassica oleracea</i> ARGOS gene members and their functions in response to abiotic stresses have not been thoroughly investigated. In this study, we identified 40 ARGOS genes via a genome wide analysis of cauliflower and two other <i>B. oleracea</i> morphotypes as well as <i>Brassica rapa</i>, <i>Brassica nigra</i>, and <i>Raphanus sativus</i>. Expression pattern analyses indicated that these genes are responsive to multiple abiotic stresses, including salinity, heat, cold, and diverse hormones. Notably, the expression of an <i>ARGOS-like</i> gene (<i>BobARL2</i>) was upregulated in cauliflower treated with 1-aminocyclopropane-1-carboxylic acid (ACC). Moreover, the overexpression of <i>BobARL2</i> decreased ethylene sensitivity, resulting in less inhibition of root elongation compared to the wild-type. Additionally, the overexpression lines exhibited enhanced salt tolerance. A yeast two-hybrid assay and luciferase complementation imaging (LCI) assay confirmed that BobARL2 can interact with Reversion-to-ethylene sensitivity Like4 (BobRTL4), which negatively regulates ethylene signal transduction. These findings advance our understanding of the evolution and functional roles of ARGOS genes in cauliflower and other Brassicaceae species, particularly in relation to abiotic stress responses, while also offering valuable insights relevant to the genetic improvement and breeding of novel varieties.