Mar1, an HMG-box protein, regulates n-alkane adsorption and cell morphology of the dimorphic yeast Yarrowia lipolytica

The dimorphic yeast Yarrowia lipolytica possesses an excellent ability to utilize n -alkane as a sole carbon and energy source. Although there are detailed studies on the enzymes that catalyze the reactions in the metabolic processes of n -alkane in Y. lipolytica , the molecular mechanism underlying the incorporation of n -alkane into the cells remains to be elucidated. Because Y. lipolytica adsorbs n -alkane, we postulated that Y. lipolytica incorporates n -alkane through direct interaction with it. We isolated and characterized mutants defective in adsorption to n -hexadecane. One of the mutants harbored a nonsense mutation in MAR1 (Morphology and n -alkane Adsorption Regulator) encoding a protein containing a high mobility group box. The deletion mutant of MAR1 exhibited defects in adsorption to n -hexadecane and filamentous growth on solid media, whereas the strain that overexpressed MAR1 exhibited hyperfilamentous growth. Fluorescence microscopic observations suggested that Mar1 localizes in the nucleus. RNA-seq analysis revealed the alteration of the transcript levels of several genes, including those encoding transcription factors and cell surface proteins, by the deletion of MAR1 . These findings suggest that MAR1 is involved in the transcriptional regulation of the genes required for n -alkane adsorption and cell morphology transition. IMPORTANCE Y. lipolytica , a dimorphic yeast capable of assimilating n -alkane as a carbon and energy source, has been extensively studied as a promising host for bioconversion of n -alkane into useful chemicals and bioremediation of soil and water contaminated by petroleum. While the metabolic pathway of n -alkane in this yeast and the enzymes involved in this pathway have been well-characterized, the molecular mechanism to incorporate n -alkane into the cells is yet to be fully understood. Due to the ability of Y. lipolytica to adsorbs to n -alkane, it has been hypothesized that Y. lipolytica incorporates n -alkane through direct interaction with it. In this study, we identified a gene, MAR1 , which plays a crucial role in the transcriptional regulation of the genes necessary for the adsorption to n -alkane and the transition of the cell morphology in Y. lipolytica . Our findings provide valuable insights that could lead to advanced applications of Y. lipolytica in n -alkane bioconversion and bioremediation.