Non-Specific Root Transport of Nutrient Gives Access to an Early Nutritional Indicator: The Case of Sulfate and Molybdate

Abstract

Under sulfur (S) deficiency, crosstalk between nutrients induced accumulation of other nutrients, particularly molybdenum (Mo). This disturbed balanced between S and Mo could provide a way to detect S deficiency and therefore avoid losses in yield and seed quality in cultivated species. Under hydroponic conditions, S deprivation was applied to Brassica napus to determine the precise kinetics of S and Mo uptake and whether sulfate transporters were involved in Mo uptake. Leaf contents of S and Mo were also quantified in a field-grown S deficient oilseed rape crop with different S and N fertilization applications to evaluate the [Mo]:[S] ratio, as an indicator of S nutrition. To test genericity of this indicator, the [Mo]:[S] ratio was also assessed with other cultivated species under different controlled conditions. During S deprivation, Mo uptake was strongly increased in B. napus. This accumulation was not a result of the induction of the molybdate transporters, Mot1 and Asy, but could be a direct consequence of Sultr1.1 and Sultr1.2 inductions. However, analysis of single mutants of these transporters in Arabidopsis thaliana suggested that other sulfate deficiency responsive transporters may be involved. Under field conditions, Mo content was also increased in leaves by a reduction in S fertilization. The [Mo]:[S] ratio significantly discriminated between the plots with different rates of S fertilization. Threshold values were estimated for the hierarchical clustering of commercial crops according to S status. The use of the [Mo]:[S] ratio was also reliable to detect S deficiency for other cultivated species under controlled conditions. The analysis of the leaf [Mo]:[S] ratio seems to be a practical indicator to detect early S deficiency under field conditions and thus improve S fertilization management.

Specificity and Plasticity of the Functional Ionome of Brassica napus and Triticum aestivum Subjected to Macronutrient Deprivation

“…In this study, the composition of the nutrient solution was adapted so as to obtain plant mineral compositions that were as close as possible to those of plants grown under field conditions ( Supplementary Data SD1 ). To do so, the mineral compositions of B. napus leaves grown under hydroponic conditions ( Maillard et al, 2015 ) were compared to the leaf mineral compositions of plants grown under field conditions (derived from the data of Sarda et al (2013) and Maillard et al, 2016b , corresponding to 194 field plots randomly harvested in France). The nutrient solution contains: 1 mM KNO 3 , 1.25 mM Ca(NO 3 ) 2, 0.2 mM KH 2 PO 4 , 0.4 mM MgSO 4 , 0.5 μM NaFe-EDTA, 50 μM NaFe-EDDHA, 10 μM H 3 BO 3 , 3 μM MnSO 4 , 3 μM ZnSO 4 , 0.7 μM CuSO 4 , 0.008 μM (NH 4 ) 6 Mo 7 O 24 , 0.1 μM CoCl 2 , 0.15 μM NiCl 2 , 0.9 mM Si(OH) 4 , 0.5 mM CaCl 2 , 0.1 mM KCl, 0.01 μM Na 2 SeO 4 , 0.1 mM K 2 SO 4 , and 0.2 mM Na 2 SiO 3 buffered to pH 6.8 with 0.36 mM CaCO 3 .…”

“…Arabidopsis Columbia wild type (Col) and sultr1.1 (SALK_093256) and sultr1.2 (sel1-8; Shibagaki et al, 2002 ) mutants previously grown under high or low S conditions by Maillard et al (2016b) were used for determination of their leaf V concentration. Briefly, Arabidopsis (Col or mutant lines) was grown for 17 days on agarose plates with a modified Long Ashton nutrient solution containing a high (0.75 mM) or low (0.075 mM) supply of sulfate.…”

“…Sulfate (SO 4 2– ), molybdate (MoO 4 2– ), and selenate (SeO 4 2– ) have also been considered as competitive anions for sulfate transporters ( Shinmachi et al, 2010 ; Schiavon et al, 2012 ). In Brassica napus (B. napus) , the up-regulation of genes encoding root sulfate transporters ( Sultr1.1 and Sultr1.2 ) in S-deficient plants enhances the uptake of MoO 4 2– and SeO 4 2– and leads to an increase in the content of these nutrient in plant tissues ( Maillard et al, 2016b ). Recently, a broader description of the nutrient interactions occurring during S deficiency ( Courbet et al, 2019 ) has highlighted other crosstalks such as between S and Fe in dinitrogen fixing species.…”

Assessment of Sulfur Deficiency under Field Conditions by Single Measurements of Sulfur, Chloride and Phosphorus in Mature Leaves

“…Plant analyses appear to be a better method for identifying S deficiency and evaluate soil fertility and crop management strategies [ 17 ]. Different indicators of S nutrition using plant analysis have been proposed, i.e., the N:S ratio [ 18 ], the SO 4 2− :total S ratio ([ 19 ], SO 4 2− [ 20 ]), total S (Pinkerton 1998 [ 21 ], the malate:SO 4 2− ratio [ 22 ], the molybdenum:S ratio [ 23 ],glutathione [ 24 ], amides [ 24 ], or expression of sulfur deficiency responsive genes[ 25 , 26 ], each presenting the advantages and drawbacks. Gene expression has potential as a sensitive indicator of S nutritional status because of its very early response of plant to S deficiency.…”

“…Studies on the reliability of the malate:SO 4 2− ratio indicate that it overestimated diagnosis of S deficiency and suggested that threshold values need to be reconsidered [ 33 , 34 ]). More recently, Maillard et al [ 23 ] have demonstrated that the [Mo]/[S] constitutes an accurate indicator to diagnose S deficiency. However, because the range of Mo leaf contents are usually low, measurements of this element need complex and senesitive laboratory methods (such as ICPMS-HR) which make difficult to use routinely this diagnostic tool.…”