Unraveling the multifaceted roles of SPL transcription factors in leaf development.

SQUAMOSA Promoter-Binding Protein-Like (SPL) transcription factors are a plant-specific family of regulatory proteins defined by a conserved SBP DNA-binding domain. They play essential roles in plant growth and development, coordinating processes such as the transition from juvenile to adult phase, branching, flowering time, and organ morphogenesis. SPL activity is tightly regulated by the miR156/157 pathway, forming a critical developmental module that integrates intrinsic and environmental cues. Recent research has expanded their known functions beyond development, revealing that SPLs also contribute to plant responses to abiotic stresses such as drought, salinity, nutrient deficiency, and temperature extremes, as well as biotic stresses including pathogen attack. Functional genomics studies across diverse species, including Arabidopsis, rice, maize, and forest trees, have uncovered both conserved and species-specific roles, emphasizing SPLs as key regulatory hubs in plant adaptation and productivity. This review summarizes advances in understanding SPL gene evolution, regulatory mechanisms, and interaction networks, with a focus on their relevance to plant architecture, leaf development, stress tolerance and crop improvement. Future applications of SPL research, particularly through gene editing, molecular breeding, and biotechnological innovations, present opportunities to optimize plant architecture, enhance resilience, and support sustainable agriculture and forestry in the face of climate change.