Expression of Oryza sativa OsSte12 transcription factor influencing antioxidant enzymes, sugar-related operons, and sugar metabolism in Escherichia coli

Ste12 is a C2H2 zinc finger protein transcription factor involved with mating pheromones and regulating protein pathways in microorganisms. Previously, we isolated Ste12 cDNA from rice (Oryza sativa) involved with sugar starvation of α-Amylase in seeds. In this study, we investigated how OsSte12regulated antioxidant enzymes, sugar-related operons, and sugar metabolism by over-expressing OsSte12 in Escherichia coli via transformation. When transformed OsSte12 E. coli was grown in glucose and lactose media, it used these substrates and expressed more activity in ascorbate peroxidase, superoxide dismutase, and sucrose synthase compared to a non-transformant (NT) E. coli strain. Moreover, transformants could be grown in lactose for higher ꞵ-galactosidase activity than NTs or in mannitol. In lactose medium, highly-expressed RNA levels of LacI and LacY were found in transformants, while LacZ gene expression in transformants was significantly reduced compared to NTs. In sucrose and fructose media, FruB and FruK transcripts were both significantly higher in transformants than in NTs, whereas FruA transcripts did not show significant differences between transformants and NTs. Compared to NTs, OsSte12transcriptions of all transformants were significantly up-regulated in response to all sugar sources, but transformants were over-expressed more highly when was grown in lactose than in other sugars. Our results are important for elucidating the regulatory mechanisms of sugars and provide new insights into physiological relevance in OsSte12 transformed E. coli.