Preliminary Studies On Riboflavin Signaling In Plant Growth And Pathogen Defense

Riboflavin (vitamin B₂) participates in many physiological processes, particularly those characterized by oxidation and reduction. The vitamin is phosphorated and combined with nucleotides to form flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which are coenzyme of many enzymes, making flavoproteins, and which play vital roles in many reactions, and especially the production of reactive oxygen intermediates (ROIs). ROIs are essential for the hypersensitive cell death, growth, and defense against pathogens and insects, as well as many aspects of responses to environmental stress. Levels of riboflavin in plants are believed to be important to these processes. As such, if riboflavin levels could be manipulated, effects of the compound on the important processes could be monitored and controlled as a consequence. This would result in great improvement of plant defense and productivity. This also could provide us with a particular insight into studying coordination of plant defense with growth regulation, which may be affected by levels of riboflavin. Studies with transgenic plants could reveal whether modulating riboflavin affects plant defense and growth signal transduction.Gene encoding riboflavin binding protein, named RfBP or RCP, has been cloned from soft-shelled turtle (Trionyx sinensis japonicus), and transformed into Arabidopsis and tobacoo. Both Southern and northern blotting analyses have confirmed the transgene integration into the plant chromosomes and the gene expression in transgenic plants. The transgenic Arabidopsis were used in this study, and four different homozygous lines A1, F6, K11 and M13 were selected from T3 or T4 generation by screening seeds on MS medium with kanamycin.The endogenous flavins, including riboflavin, FMN and FAD, determined by HPLC. in transgenic lines were much higher than those in the wild type. Increase in flavin concentrations coincided with the expression of RCP; the higher expression of the gene, the more increase in endogenous flavins. And this increase brings many benefits. The transgenic lines show faster growth in root, much healthy development, larger individuals...