Overexpression of BoSULTR1;1/BoSULTR1;2 promotes glucosinolate accumulation and enhances stress tolerance in broccoli

Abstract

SULTR1;1 and SULTR1;2 are high-affinity sulphate transporters that are crucial for sulphate uptake from the soil. Nevertheless, the impact of sulphate absorption mediated by SULTR1;1 and SULTR1;2 on the metabolism of sulfur-containing compounds as well as the physiological processes they are involved in is not yet fully understood. In this study, we cloned the BoSULTR1;1 and BoSULTR1;2 genes from broccoli (Brassica oleracea var. italica). Overexpression of BoSULTR1;1/BoSULTR1;2 in Arabidopsis enhanced sulphate uptake and assimilation, without accumulating the sulphate assimilation product cysteine. Overexpression of BoSULTR1;1/BoSULTR1;2 also triggered the upregulation of genes responsible for the biosynthesis of another two sulfur-containing compounds, methionine and glutathione, without leading to their accumulation, rather, it led to the accumulation of the downstream secondary metabolites, glucosinolates. Under normal growth conditions, BoSULTR1;1 and BoSULTR1;2 are specifically expressed in the roots. However, certain treatments such as wounding, PEG 6000-simulated drought stress, and methyl jasmonate can induce the expression of the two genes in the aerial parts, indicating that BoSULTR1;1/BoSULTR1;2 may not only regulate sulfur uptake but also potentially control the distribution of sulphate in the above-ground tissues and participate in defense against certain adverse environmental cffigonditions. Given that glucosinolates are crucial defense compounds against both biotic and abiotic stresses, we detected stress tolerance in plants overexpressing BoSULTR1;1/BoSULTR1;2. The results revealed that overexpression of BoSULTR1;1/BoSULTR1;2 in Arabidopsis significantly enhanced resistance to Helicoverpa armigera, bacteria pathogen Pseudomonas syringae pv. tomato DC3000 and drought stress. Similar results were observed when BoSULTR1;1/BoSULTR1;2 was overexpressed in broccoli, indicating a conservative role of BoSULTR1;1/BoSULTR1;2 in Brassicaceae plants. In conclusion, BoSULTR1;1 and BoSULTR1;2 are effective candidate genes for enhancing sulfur uptake and improving stress resistance in Brassicaceae plants such as broccoli. Their potential applications in agricultural production are highly promising.