On July 6, Prof. Bernhard Grimm from Humboldt University of Berlin visited the School of Agriculture and Biology and delivered an academic lecture titled “Flavin Synthesis and Transport in *A. thaliana*.” Prof. Grimm is an internationally renowned scientist in the field of chlorophyll biosynthesis regulation and chloroplast development. The seminar was chaired by Prof. Wu Guozhang from the School.

In plant cells, riboflavin (vitamin B₂) serves as a precursor to two key coenzymes—flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)—and is widely involved in core metabolic processes. Throughout evolution, plant cells have retained independent flavin biosynthesis pathways in the cytosol, chloroplasts, and mitochondria, with distinct enzymes catalyzing synthesis and hydrolysis reactions.

Prof. Grimm first introduced four enzymes involved in flavin synthesis and hydrolysis currently under investigation in his laboratory: FHRK and FADS, which possess both synthetic and hydrolytic activities, as well as the FAD synthases RIBF1 and RIBF2. Regarding the mechanistic question of how FHRK and FADS achieve their dual synthetic and hydrolytic functions, the research group is actively exploring the regulatory mechanisms underlying their protein functions.

Given the compartmentalized nature of the biosynthetic pathways, Prof. Grimm proposed the existence of proteins that mediate flavin transport between the cytosol and chloroplasts. His team has identified a novel flavin transporter in plants, localized to mitochondria and peroxisomes. The precise functional mechanisms of this transporter remain a key focus of ongoing research.

Following the lecture, faculty and students engaged in lively discussion. Prof. Grimm exchanged insights with the audience on topics including the functions and regulatory mechanisms of FHRK, FAD, RIBF1/RIBF2, and the potential transporter proteins.