Multiple Signals Can Be Integrated into Pathways of Blue-Light-Mediated Floral Transition: Possible Explanations on Diverse Flowering Responses to Blue Light Manipulation

Blue light (BL) plays a crucial role in regulating floral transition and can be precisely manipulated in controlled-environment agriculture (CEA). However, previous studies on BL-mediated flowering in CEA have produced conflicting results, likely due to species-specific responses and variations in experimental conditions (such as light spectrum and intensity) as summarized in our recent systematic review. This speculation still lacks a mechanistic explanation at the molecular level. By synthesizing recent advances in our understanding of the signaling mechanisms underlying floral transition, this review highlights how both internal signals (e.g., hormones, carbohydrates, and developmental stage) and external cues (e.g., light spectrum, temperature, nutrients, stress, and magnetic fields) are integrated into the flowering pathway mediated by BL. Key signal integration nodes have been identified, ranging from photoreceptors (e.g., cryptochromes) to downstream components such as transcription factors and central flowering regulator, FLOWERING LOCUS T (FT). This signal integration offers a potential mechanistic explanation for the previously inconsistent findings, which may arise from interspecies differences in photoreceptor composition and variation in the expression of downstream components influenced by hormonal crosstalk, environmental conditions, and developmental stage, depending on the specific context. This review provides novel molecular insights into how BL modulates floral transition through interactions with other signals. By systematically compiling and critically assessing recent research findings, we identify key research gaps and outline future directions, particularly the need for more studies in agriculturally important crops. Furthermore, this review proposes a conceptual framework for optimizing BL-based lighting strategies and exploring underexamined interaction factors in the regulation of flowering.