Plant BTB (Broad-Complex, Tramtrack, and Bric-à-Brac) Proteins: Structural Features, Biological Functions, and Roles...

As sessile organisms, plants must continuously perceive and integrate external environmental cues with internal developmental signals to optimize growth, reproduction, and survival. Central to this adaptive capacity is the ubiquitin-proteasome system (UPS), the primary pathway for selective protein degradation in eukaryotes. Within the UPS, BTB (Broad-Complex, Tramtrack, and Bric-à-brac) proteins serve as critical substrate adaptors for the Cullin3 (CUL3)-based E3 ubiquitin ligase complex. These proteins play indispensable roles in plant growth, development, hormone signaling, and responses to abiotic stresses. Recent advances have revealed the remarkable functional versatility of BTB proteins, implicating them in the regulation of photomorphogenesis, root architecture, flowering time, stress resilience, and yield-related traits. With 80 BTB-encoding genes in Arabidopsis thaliana and key orthologs identified in major crops-including of rice (Oryza sativa), soybean (Glycine max), and maize (Zea mays)-BTB proteins act as molecular "bridges" that integrate developmental programs with environmental stress signals. This review summarizes the structural features, classification, and multifaceted functions of plant BTB proteins, with an emphasis on their roles in growth regulation, abiotic stress tolerance, light signaling, and agricultural productivity. We further discuss their mechanisms in ubiquitin-dependent proteolysis, transcriptional regulation, and signal integration, offering insights into their potential as targets for engineering climate-resilient crops and advancing sustainable agriculture.