Heat and hypoxia stresses enhance the accumulation of aliphatic glucosinolates and sulforaphane in broccoli sprouts

In this study, aliphatic glucosinolates and sulforaphane were accumulated in broccoli sprouts under the stresses of heat, hypoxia and heat plus hypoxia. Glucoraphanin content in 7-day-old broccoli sprouts under heat, hypoxia and heat plus hypoxia stresses enhanced by 1.39-, 1.10- and 1.16-fold compared with the control, respectively; meanwhile, glucoerucin content increased by 1.87-, 4.17- and 3.24-fold, respectively. Aliphatic glucosinolate content was enhanced by heat stress due to the increasing expression of Elong, CYP83A1 and FMO (GS-OX1) . However, under hypoxia and heat plus hypoxia stresses, the expression levels of Elong, CYP83A1, UGT74B1, ST5b and AOP2 related to aliphatic glucosinolates biosynthesis were dramatically up-regulated. Heat, hypoxia and heat plus hypoxia stresses enhanced sulforaphane formation in 7-day-old sprouts by 153.73, 95.15 and 86.95 % compared with the control, respectively. However, heat plus hypoxia stress did not exhibit the synergistic effect of heat and hypoxia stresses. These results indicated that heat and hypoxia stresses were feasible strategies to enhance the accumulation of aliphatic glucosinolates and sulforaphane in broccoli sprouts.