The pleiotropic transcriptional regulator NlpR contributes to the modulation of nitrogen metabolism, lipogenesis and triacylglycerol accumulation in oleaginous rhodococci.

HERNÁNDEZ MA, LARA J, GAGO G, GRAMAJO H, ALVAREZ HM

MOLECULAR MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2016

0950-382X

The regulatory mechanisms involved in lipogenesisand triacylglycerol (TAG) accumulation are largelyunknown in oleaginous rhodococci. In this study aregulatory protein (here called NlpR: Nitrogen lipidRegulator), which contributes to the modulation ofnitrogen metabolism, lipogenesis and triacylglycerolaccumulation in oleaginous rhodococci was identified.Under nitrogen deprivation conditions, in whichTAG accumulation is stimulated, the nlpR gene wassignificantly upregulated, whereas a significantdecrease of its expression and TAG accumulationoccurred when cerulenin was added. The nlpRdisruption negatively affected the nitrate/nitritereduction as well as lipid biosynthesis undernitrogen-limiting conditions. In contrast, its overexpressionincreased TAG production during cultivationof cells in nitrogen-rich media. A putative?NlpR-binding motif? upstream of several genesrelated to nitrogen and lipid metabolisms was found.The nlpR disruption in RHA1 strain led to a reducedtranscription of genes involved in nitrate/nitriteassimilation, as well as in fatty acid and TAG biosynthesis.Purified NlpR was able to bind to narK, nirD,fasI, plsC and atf3 promoter regions. It was suggestedthat NlpR acts as a pleiotropic transcriptionalregulator by activating of nitrate/nitrite assimilationgenes and others genes involved in fatty acid andTAG biosynthesis, in response to nitrogendeprivation.