Genome-wide identification and expression profiling of the SBP/miR156 module in response to pathogen stress in sisal...

Sisal (Agave sisalana) productivity is severely threatened by purple leaf roll and zebra stripe diseases. The SQUAMOSA PROMOTER BINDING PROTEIN (SBP)-box gene family is an important regulator of plant defense against biotic stresses, yet its role in sisal immunity remains poorly understood. We performed a genome-wide identification of AhSBP genes in the A. sisalana genome and analyzed their expansion mechanisms through phylogenetic and synteny modeling. Comparative transcriptomics, promoter cis-element analysis, and RT-qPCR validation were further integrated to elucidate the regulatory mechanisms of the miR156-AhSBP module under pathogen stress. A total of 45 AhSBP genes were identified, revealing a lineage-specific expansion mainly driven by segmental duplication (70%). Among these, 18 AhSBP genes were identified as putative miR156 targets. Transcriptomic and qPCR analyses showed that asi-miR156 is significantly induced in susceptible cultivars, leading to the suppression of its direct targets, such as AhSBP9 and AhSBP38. In contrast, resistant cultivars maintain low miR156 levels, allowing the activation of the SBP-mediated defense program. Our findings suggest that the miR156-AhSBP module serves as a primary regulatory hub coordinating sisal's immune homeostasis, while members like AhSBP17 and AhSBP34 likely function as downstream effectors. This study provides a comprehensive understanding of the AhSBP gene family and offers potential genetic targets for engineering broad-spectrum disease resistance in sisal.