Brassinosteroids are involved in volatile compounds biosynthesis related to MdBZR1 in ‘Ruixue’ (Malus × domestica Borkh.) fruit

Abstract

Aroma is a crucial quality attribute of apple fruit, mainly determined by volatile compounds. However, to our knowledge, the physiological and molecular roles of brassinosteroids (BRs) in volatile compound biosynthesis had not been elucidated. In this study, 24-epibrassinolide (EBR) inhibited fruit firmness and ethylene production and delayed fruit ripening. Total soluble solids, fructose content, glucose, and sucrose content were inhibited by EBR treatment. Most importantly, enzyme activity, volatile compound production, and genes involved in volatiles biosynthesis were suppressed compared with those in the control after EBR treatment. Furthermore, volatile compounds production and biosynthesis gene expressions was decreased by the overexpression of MdBZR1, whereas opposite results were observed when MdBZR1 was silenced. Notably, OE-MdBZR1 calli showed lower volatile compound content than that of the control calli by EBR treatment. Collectively, these results indicate that BR activate MdBZR1 expression, which in turn inhibited volatile compound production.