Direct and indirect effects of RNA interference against pyridoxal kinase and pyridoxine 5′-phosphate oxidase genes in Bombyx mori

Abstract

Vitamin B6 comprises six interconvertible pyridine compounds (vitamers), among which pyridoxal 5′-phosphate is a coenzyme involved in a high diversity of biochemical reactions. Humans and animals obtain B6 vitamers from diet, and synthesize pyridoxal 5′-phosphate by pyridoxal kinase and pyridoxine 5′-phosphate oxidase. Currently, little is known on how pyridoxal 5′-phosphate biosynthesis is regulated, and pyridoxal 5′-phosphate is supplied to meet their requirement in terms of cofactor. Bombyx mori is a large silk-secreting insect, in which protein metabolism is most active, and the vitamin B6 demand is high. In this study, we successfully down-regulated the gene expression of pyridoxal kinase and pyridoxine 5′-phosphate oxidase by body cavity injection of synthesized double-stranded small interfering RNA to 5th instar larvae of Bombyx mori, and analyzed the gene transcription levels of pyridoxal 5′-phosphate dependent enzymes, phosphoserine aminotransferase and glutamic-oxaloacetic transaminase. Results show that the gene expression of pyridoxal kinase and pyridoxine 5′-phosphate oxidase has a greater impact on the gene transcription of enzymes using pyridoxal 5′-phosphate as a cofactor in Bombyx mori. Our study suggests that pyridoxal 5′-phosphate biosynthesis and dynamic balance may be regulated by genetic networks.