Scientists discovered a protein in Arabidopsis (thale cress) that acts as a traffic controller for riboflavin (vitamin B2), steering how much of it reaches flowers, seed pods, and seeds. Without this protein, riboflavin over-accumulates in reproductive organs — revealing that plants actively regulate where this essential nutrient goes, rather than letting it diffuse freely.
1
AtPUP5, a plasma membrane protein, transports riboflavin and (less efficiently) FMN into cells, but struggles to move FAD, suggesting selectivity among related vitamin B2 forms.
2
Plants lacking AtPUP5 accumulate excess riboflavin specifically in reproductive organs — flowers, seed pods, and seeds — regardless of whether extra riboflavin was supplied externally.
3
AtPUP5 is not required for whole-plant riboflavin uptake, showing its role is spatially specific: local redistribution within reproductive tissues, not global absorption.
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