Abstract
Plants take up sulfur (S), an essential element for all organisms, as sulfate, which is mainly attributed to the function of SULTR1;2 in Arabidopsis. A disruption mutant of SULTR1;2, sel1-10, has been characterized with phenotypes similar to plants grown under sulfur deficiency (−S). Although the effects of −S on S metabolism were well investigated in seedlings, no studies have been performed on mature Arabidopsis plants. To study further the effects of −S on S metabolism, we analyzed the accumulation and distribution of S-containing compounds in different parts of mature sel1-10 and of the wild-type (WT) plants grown under long-day conditions. While the levels of sulfate, cysteine, and glutathione were almost similar between sel1-10 and WT, levels of glucosinolates (GSLs) differed between them depending on the parts of the plant. GSLs levels in the leaves and stems were generally lower in sel1-10 than those in WT. However, sel1-10 seeds maintained similar levels of aliphatic GSLs to those in WT plants. GSL accumulation in reproductive tissues is likely to be prioritized even when sulfate supply is limited in sel1-10 for its role in S storage and plant defense.
Highlights
Sulfur (S) is an essential macronutrient for all organisms
To investigate the metabolic changes occurring in mature sel1-10 plants, we initially observed the growth phenotypes of sel1-10 plants (Figure 1)
Visible differences in shoot phenotype were not observed between WT and sel1-10 plants (Figure 1a,b), a significant decrease was observed in the primary stem diameters of sel1-10 plants compared to those of the WT, while the plant heights were similar between WT and sel1-10 plants (Figure 1c)
Summary
Sulfur (S) is an essential macronutrient for all organisms. Plants take up inorganic sulfate as the major S source and assimilate it into a variety of S-containing organic compounds [1,2]. Many of the S-containing compounds biosynthesized in plants are beneficial to health, such as methionine (an essential amino acid for animals), glutathione (a redox controller), and various secondary compounds with specific functions [2]. Glucosinolates (GSLs) are the major S-containing secondary compounds biosynthesized in Brassicaceae, that act as defense compounds against insects and pathogens [3,4,5]. Depending on their amino acid precursors, most GSLs accumulated in Arabidopsis are classified into aliphatic and indolic GSLs (iGSLs) synthesized from methionine and tryptophan, respectively [3,4,5]. Understanding GSL accumulation in plant tissues would contribute to improved food quality in Brassica crops
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