Drought-responsive transcriptional networks in West African sorghum landraces under progressive water deficit

Abstract

Sorghum landraces cultivated across the West African Sahel display marked variation in drought tolerance, yet the transcriptional basis of this variation remains poorly characterised. We subjected twelve landraces and two elite cultivars to progressive water deficit under controlled conditions and profiled leaf transcriptomes at four stress thresholds. Weighted gene co-expression network analysis resolved six modules significantly associated with stomatal conductance and osmotic adjustment. Two modules, enriched for NAC and DREB transcription factors, were induced two to three days earlier in tolerant landraces than in elite cultivars, and this earlier induction predicted biomass retention under terminal drought better than any single physiological marker. A third module linked to cuticular wax biosynthesis was constitutively higher in three Sahelian landraces regardless of treatment. These results identify anticipatory regulation, rather than response magnitude, as the discriminating feature of drought tolerance in this germplasm, and nominate specific regulatory modules for marker-assisted selection.