Evidence for loss and adaptive reacquisition of alcoholic fermentation in an early-derived fructophilic yeast lineage

Abstract

23Fructophily is a rare trait that consists in the preference for fructose over other carbon sources. 24Here we show that in a yeast lineage (the Wickerhamiella/Starmerella, W/S clade) formed by 25 fructophilic species thriving in the floral niche, the acquisition of fructophily is part of a wider 26 process of adaptation of central carbon metabolism to the high sugar environment. Coupling 27 comparative genomics with biochemical and genetic approaches, we show that the alcoholic 28 fermentation pathway was profoundly remodeled in the W/S clade, as genes required for 29 alcoholic fermentation were lost and subsequently re-acquired from bacteria through horizontal 30 gene transfer. We further show that the reinstated fermentative pathway is functional and that an 31 enzyme required for sucrose assimilation is also of bacterial origin, reinforcing the adaptive 32 nature of the genetic novelties identified in the W/S clade. This work shows how even central 33 carbon metabolism can be remodeled by a surge of HGT events.