Calcium affects glucoraphanin metabolism in broccoli sprouts under ZnSO 4 stress.

CaCl ₂ , Ca ²⁺ chelator (EGTA) and Ca ²⁺ channel blocker (verapamil) were used to investigate mechanism of glucoraphanin metabolism in broccoli sprouts under ZnSO ₄ stress. CaCl ₂ treatment promoted sprout growth, reduced MDA (malonaldehyde) content and electrolyte leakage in sprouts under ZnSO ₄ stress. The highest MDA content and electrolyte leakage were obtained in ZnSO ₄ plus verapamil-treated sprouts. In addition, ZnSO ₄ plus CaCl ₂ treatment significantly enhanced glucoraphanin content and sulforaphane formation, while an opposite result was observed after ZnSO ₄ plus EGTA treatment; which were further supported by expression of glucoraphanin biosynthetic and hydrolytic genes as well as myrosinase (MYR) and epithiospecifier protein (ESP) activities. These results indicated that exogenous and endogenous calcium promoted glucoraphanin biosynthesis and the conversion rate of glucoraphanin into sulforaphane. Verapamil treatment also stimulated glucoraphanin biosynthesis, but exerted an adverse influence on sulforaphane formation from the hydrolysis of glucoraphanin because of much higher ESP expression and ESP activity than ZnSO ₄ treatment.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier Ltd. All rights reserved.)