Sulphur-mediated iron homeostasis in four tetraploid wheats (Triticum turgidum L.)

Sulphur (S) deficiency is known to hinder iron (Fe) uptake and distribution in wheat, mainly by reducing phytosiderophores (PS) synthesis and release. This study investigated the impact of S supply on Fe accumulation in four tetraploid wheat genotypes with different genetic backgrounds: a modern genotype, Svevo (Triticum turgidum subsp. durum), two ancient Khorasan wheats, Turanicum_21 and Etrusco (T. turgidum subsp. turanicum) and an ancient Polish wheat, Polonicum_2 (T. turgidum subsp. polonicum). Plants were grown hydroponically for 20 days under adequate (S = 1.2 mM) or limiting (L = 0.06 mM) sulfate levels, while receiving sufficient Fe (80 μM). Most genotypes exhibited reduced Fe accumulation under low S conditions, as expected. However, Polonicum_2 showed a unique response, accumulating significantly more Fe in both shoots and roots. This increased Fe accumulation was associated with a higher rate of PS release and upregulation of both TdYSL15 and TdIRO2 in roots of Polonicum_2, suggesting altered regulation of Fe deficiency responses. However, the expression pattern of TdIDEF1 was not correlated with TdYSL15 expression in this plant, suggesting the involvement of additional regulatory pathways beyond Fe supply. Finally, there was a strong correlation between O-acetylserine(thiol)lyase activity in shoot tissues and PS release rate across all genotypes. There is increased interest in Khorasan and Polish wheats as alternative crops for marginal areas, hence, these findings are noteworthy from a biofortification perspective and could potentially lead to innovations in agriculture that benefit food security.