Application of Tryptophan and Methionine in Broccoli Seedlings Enhances Formation of Anticancer Compounds Sulforaphane and Indole-3-Carbinol and Promotes Growth.

Broccoli is a popular cruciferous vegetable that is well known for its abundant health-promoting biochemicals. The most important of these beneficial biochemicals are glucosinolates, including glucoraphanin and glucobrassicin. Glucoraphanin and glucobrassicin can be broken down by myrosinases into sulforaphane and indole-3-carbinol, which have been demonstrated to have potent cancer-preventive properties. Efforts to increase glucoraphanin in broccoli seedlings have long been a focus; however, increasing glucoraphanin and glucobrassicin simultaneously, as well as enhancing myrosinase activity to release more sulforaphane and indole-3-carbinol, have yet to be investigated. This study aims to investigate the impact of the combined application of tryptophan and methionine on the accumulation of sulforaphane and indole-3-carbinol, as well as their precursors. Furthermore, we also examined whether this application has any effects on seedling growth and the presence of other beneficial compounds. We found that the application of methionine and tryptophan not only increased the glucoraphanin content by 2.37 times and the glucobrassicin content by 3.01 times, but that it also caused a higher myrosinase activity, resulting in a1.99 times increase in sulforaphane and a 3.05 times increase in indole-3-carbinol. In addition, better plant growth and an increase in amino acids and flavonoids were observed in broccoli seedlings with this application. In conclusion, the simultaneous application of tryptophan and methionine to broccoli seedlings can effectively enhance their health-promoting value and growth. Our study provides a cost-effective and multi-benefit strategy for improving the health value and yield of broccoli seedlings, benefiting both consumers and farmers.

Overexpression of BoLSU1 and BoLSU2 Confers Tolerance to Sulfur Deficiency in Arabidopsis by Manipulating Glucosinolate Metabolism.

Sulfur is an essential element for plant growth, development and resistance to environmental stresses. Glucosinolates (GSLs), a group of sulfur rich secondary metabolites found in Brassicaceae plants, are known for their defensive properties against pathogens and herbivores. Due to their integration of a large proportion of total sulfur, their biosynthesis and degradation are closely linked to sulfur metabolism. It has been demonstrated that GSLs can be broken down to release sulfur and facilitate the production of other thio-metabolites when the plant is under stress. However, the regulation of this process is still not fully understood. In this study, we constructed two broccoli LSU (low sulfur responsive) gene overexpressing lines, 35S::BoLSU1 and 35S::BoLSU2, to detect changes in GSL metabolism after sulfur deficiency treatment. The results showed that BoLSU1 and BoLSU2 inhibit the biosynthesis of aliphatic GSLs, while also promoting their degradation and increasing the content of glutathione (GSH), leading to the reallocation of sulfur from the GSL pool to other thio-metabolites such as GSH. Furthermore, this regulation of GSL metabolism mediated by BoLSU1 and BoLSU2 is found to be dependent on myrosinases BGLU28 and BGLU30. Our study provides insight into the physiological role of LSU proteins and their regulation of sulfur metabolism.

Overexpression of LSU1 and LSU2 confers cadmium tolerance by manipulating sulfur metabolism in Arabidopsis.

Phytoremediation using plants is an environmentally friendly and cost-effective strategy for removing cadmium (Cd) from soil. Plants used for phytoremediation must have a high Cd accumulation capacity and strong Cd tolerance. Therefore, understanding the molecular mechanism of Cd tolerance and accumulation in plants is of great interest. In response to Cd exposure, plants produce various thio-rich compounds, such as glutathione, phytochelatins, and metallothioneins, which play important roles in Cd immobilization, sequestration, and detoxification. Therefore, sulfur (S) metabolism is crucial for Cd tolerance and accumulation. In this study, we report that the overexpression of low-S responsive genes, LSU1 and LSU2, confers Cd tolerance in Arabidopsis. First, LSU1 and LSU2 promoted S assimilation under Cd stress. Second, LSU1 and LSU2 inhibited the biosynthesis and promoted the degradation of aliphatic glucosinolates, which could limit the consumption and enhance the release of S, thus, facilitating the production of the S-rich metabolites, glutathione, phytochelatins, and metallothioneins. We further demonstrated that the Cd tolerance mediated by LSU1 and LSU2 was dependent on the myrosinases BGLU28 and BGLU30, which catalyze the degradation of aliphatic glucosinolates. In addition, the overexpression of LSU1 and LSU2 improved Cd accumulation, which has great potential for the phytoremediation of Cd-contaminated soil.