Chimeric receptors as a signaling engineering approach towards xylose sensing in Saccharomyces cerevisiae

BRUNA C. BOLZICO, VIKTOR PERSSON, MARIE GORWA-GRAUSLUND, RAÚL N. COMELLI

Conferencia; 8th Conference on Physiology of Yeasts and Filamentous Fungi (PYFF8); 2023

University College Cork (UCC)

Xylose, the major pentose sugar present in lignocellulosic hydrolysates, is a non-native carbon source in Saccharomyces cerevisiae. Efforts in xylose metabolism have been focused on introducing heterologous transporters and enzymes that enable xylose assimilation and the conversion of the pentose into ethanol. However, the lack of a specific signaling pathway for xylose recognition as a fermentable sugar is also possibly causing lower consumption and fermentation rates, in comparison to glucose, the preferred substrate [1]. In the present work, one of the glucose regulatory signals was engineered to respond to xylose with the long-term goal of improving the efficiency of xylose utilization. The strategy was based on constructing chimeric receptors that could simulate glucose signals triggered by Snf3 and Rgt2 pathway, but in the presence of extracellular xylose. More specifically, the C-terminal domains of Snf3 and Rgt2 glucose sensors were fused to the transmembrane domain of a xylose transporter protein, and we investigated to what extent the generated chimeric proteins could activate the pathway in response to xylose. This was achieved by recording fluorescence in Saccharomyces cerevisiae GFP-reporter strains, using flow cytometry combined with biosensors that were previously established to monitor the glucose sensing signals [2]. In the present contribution, we report on the results of this approach and how the strategy can help elucidate whether the signal originates from extracellular xylose and/or from the capacity of the chimeric proteins to internalize the sugar. Overall, this research provides a novel approach for engineering xylose-sensing ability in S. cerevisiae strains.