Interaction between Sulfate and Selenate in Tetraploid Wheat (Triticum turgidum L.) Genotypes

{"Background": "Selenium (Se) is an essential micronutrient for humans, with a recommended daily intake of 55 \u00b5g. Se deficiency affects over 1 billion people worldwide and is linked to thyroid dysfunction, immune impairment, and increased risk of chronic inflammatory and degenerative diseases. Since plant-derived foods are the primary Se source for humans, biofortification of staple crops like wheat\u2014the second most cultivated crop globally\u2014represents a promising strategy. Selenate (SeO\u2084\u00b2\u207b) is chemically similar to sulfate and is taken up by plants via root sulfate transporters (SULTRs). Sulfate availability generally inhibits selenate uptake, while sulfur deficiency upregulates sulfate transporters and increases Se uptake. This study aimed to characterize the Se-S interaction during root uptake by measuring high-affinity sulfate transporter gene expression and to explore whether modulating S availability could enhance Se accumulation in four tetraploid wheat genotypes: the modern durum wheat Svevo and three ancient Khorasan genotypes (Kamut, Turanicum 21, and Etrusco).", "Methods": "Seeds of four Triticum turgidum genotypes (Svevo, Tur-21, Kamut, Etrusco) were germinated and grown hydroponically in a growth chamber (27/20\u00b0C, 14/10 h day/night, 80% relative humidity, 200 mmol m\u207b\u00b2 s\u207b\u00b9 PAR). Plants were exposed to two sulfate levels (S: 1.2 mM and L: 0.06 mM) and three selenate levels (0, 10, and 50 \u00b5M). After 20 days, plants were harvested and separated into roots and shoots. Chlorophyll content was estimated using a SPAD meter on the first fully expanded leaf. Element concentrations (Ca, Cu, Fe, K, Mg, Mn, Mo, Na, P, S, Se, Zn) were quantified by ICP-OES after microwave digestion. Total RNA was extracted from shoots and roots, and qRT-PCR was performed to measure expression of TdSultr1.1 and TdSultr1.3 high-affinity sulfate transporter genes, using \u03b2-actin as the housekeeping gene and the 2\u207b\u2206\u2206Ct method. Statistical analysis used one-way and two-way ANOVA with LSD and Fisher's tests at p < 0.05. PCA was performed on shoot ionomic data.", "Key Results": "Kamut showed the best growth and biomass production under all conditions. Low S supply (L) caused significant shoot biomass reduction only in Svevo and Kamut at 50 \u00b5M Se (\u221240% and \u221220%, respectively). Low S without Se stimulated root growth in all genotypes, most notably in Svevo (2.5-fold) and Etrusco (2-fold). Adding 50 \u00b5M Se reversed this root growth stimulation, with inhibition ranging from 10% in Tur-21 to 50% in Etrusco. Chlorophyll content (SPAD) was reduced by low S without Se by 14%, 15%, 6%, and 10% in Svevo, Tur-21, Kamut, and Etrusco, respectively. Under sufficient S, 50 \u00b5M Se reduced SPAD by 13% in Svevo and 14% in Kamut. S accumulation was strongly enhanced by Se application, particularly in Etrusco: under low S with 50 \u00b5M Se, Etrusco roots reached 98.76 mg S g\u207b\u00b9 DW and shoots 23.45 mg S g\u207b\u00b9 DW\u201423-fold and 7-fold higher than Svevo control, respectively. Low S supply clearly stimulated Se accumulation in all genotypes. Under L50, shoot Se reached 4.09 \u00b5g g\u207b\u00b9 DW in Svevo, 3.17 in Tur-21, 3.45 in Kamut, and 3.68 in Etrusco. TdSultr1.1 was upregulated in shoots and roots of Etrusco and Kamut compared to Svevo (up to 5.85-fold in Kamut shoots), while TdSultr1.3 expression was drastically reduced in all three turanicum genotypes. PCA separated the four genotypes into distinct clusters in all conditions, with Fe, Mn, and Zn contributing positively to PC1. Low S reduced Fe accumulation by 40\u201350% in most genotypes. Low Se (10 \u00b5M) increased Fe concentration in Svevo and Kamut shoots under sufficient S by 50% and 60%, respectively. High Se (50 \u00b5M) reduced Fe in Tur-21 and Etrusco shoots under sufficient S by 60% and 54%, respectively.", "Clinical Implications": "This study demonstrates that modulating sulfur availability can significantly enhance selenium accumulation in wheat, offering a practical strategy for Se biofortification of staple crops. The identification of genotypic variation\u2014particularly the superior Se and S accumulation capacity of the Etrusco genotype\u2014highlights the potential of exploiting wheat biodiversity for nutritional improvement. The finding that low-dose Se treatment also enhanced iron accumulation in some genotypes suggests possible co-benefits for addressing multiple micronutrient deficiencies simultaneously. These insights could inform sustainable agricultural practices to improve human nutrition and health, particularly in regions where Se deficiency is prevalent."}