Sulfur deficiency-induced glucosinolate catabolism attributed to two β-glucosidases, bglu28 and bglu30, is required for plant growth maintenance under sulfur deficiency

Sulfur (S) is an essential element for plants, and S deficiency causes severe growth retardation. Although the catabolic process of glucosinolates (GSLs), the major S-containing metabolites specific to Brassicales including Arabidopsis, has been recognized as one of the S deficiency (S) responses in plants, the physiological function of this metabolic process is not clear. Two β-glucosidases (BGLUs), BGLU28 and BGLU30, are assumed to be responsible for this catabolic process as their transcript levels were highly upregulated byS. To clarify the physiological function of BGLU28 and BGLU30 and their roles in GSL catabolism, we analyzed the accumulation of GSLs and other S-containing compounds in the single and double mutant lines of BGLU28 and BGLU30 and in wild-type plants under different S conditions. GSL levels were highly increased, while the levels of sulfate, cysteine, glutathione and protein were decreased in the double mutant line of BGLU28 and BGLU30 (bglu28/30) underfiS. Furthermore, transcript level of Sulfate Transporter1;2, the main contributor of sulfate uptake from the environment, was increased in bglu28/30 mutants underfiS. With these metabolic and transcriptional changes, bglu28/30 mutants displayed obvious growth retardation underfiS. Overall, our results indicate that BGLU28 and BGLU30 are required for-S-induced GSL catabolism and contribute to sustained plant growth underfiS by recycling sulfate to primary S metabolism.