2025/03/28 by Mariana Inés Costa, Micaela Cerletti, Roberto A. Paggi +5 · 1 voice
Biochemistry, Genetics and Molecular Biology · Medicine · Neuroscience · #Barrier Structure and Function Studies #Cell Adhesion Molecules Research #S100 Proteins and Annexins
paper · pdf · doi:10.3389/fmicb.2025.1547649
openalex publication_date 2025/03/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23
Introduction Rhomboid proteases are intramembrane serine proteases that play a key role in regulating membrane proteins across all domains of life. However, their function in archaea remains poorly understood. The model halophilic archaeon Haloferax volcanii encodes two rhomboid homologs, rho1 (HVO1474) and rho2 (HVO0727). Previous studies indicated that the deletion of rho2 resulted in mild alterations in motility, adhesion, biofilm formation, and cell morphology, suggesting potential functional compensation by rho1 . Materials and methods To investigate the role of these proteases, we generated single (Δ rho1 ) and double (Δ rho1 Δ rho2 ) deletion mutants. Phenotypic characterization included viability assays, motility tests, adhesion and biofilm formation studies, as well as morphological analysis using microscopy. Functional overlap between rho1 and rho2 was evaluated through genetic complementation/overexpression experiments in which each gene was expressed in trans in the mutant backgrounds. Results Both Δ rho1 and Δ rho1 Δrho2 mutants were viable, indicating that these genes are not essential in H. volcanii. The Δ rho1 mutant exhibited increased motility, enhanced biofilm formation, reduced adhesion to glass surfaces, and significant morphological alterations, particularly in trace element-deficient conditions. The double mutant (Δ rho1 Δ rho2 ) showed increased adhesion to surfaces, mild motility reduction, and fewer morphological abnormalities compared to Δ rho1 . Complementation assays revealed that both rho1 and rho2 could restore motility in Δ rho2 and adhesion in Δrho1. However, only rho1 was able to complement the morphological defects, suggesting a degree of functional divergence between these homologs. Discussion This work highlights the role of rhomboid proteases in regulating critical cell surface processes in H. volcanii , including biofilm formation, surface adhesion, and cell shape determination. The ability of rho1 and rho2 to compensate for each other in certain functions while maintaining distinct roles underscores a complex regulatory interplay. Future research will focus on identifying natural substrates and elucidating the molecular mechanisms underlying rhomboid protease function in haloarchaea.