Exogenous methyl jasmonate (MeJA) mediated carbohydrate metabolism in apple fruit during ripening

Carbohydrate metabolism plays an essential role in mediating quality and ripening of postharvest fruit. Previous work has demonstrated the regulatory role of methyl jasmonate (MeJA) in ripening of apple fruit. However, the role of MeJA in mediating carbohydrate metabolism of ripening apple fruit is unexplored. Our work investigated impacts of MeJA treatment (1.5 mM) on carbohydrate metabolism of apple fruit during ripening at 20 ± 0.5 °C. Our data indicated that, compared with controls, exogenous MeJA decreased starch content by increasing total amylase (AM), α-amylase (α-AM) and β-amylase (β-AM) activities during ripening. It also reduced sorbitol content by enhancing NADP-sorbitol dehydrogenase (NADP-SDH) and NAD-sorbitol dehydrogenase (NAD-SDH) activities during ripening. At the late ripening stage, exogenous MeJA promoted accumulation of sucrose, glucose and fructose. Meanwhile, it increased activities of sucrose phosphate synthase (SPS) and vacuolar acid invertase (vAINV) but decreased activities of neutral invertase (NINV), fructokinase (FRK) and hexokinase (HXK). Sucrose synthases (SUSY) activity was fluctuated after MeJA treatment during ripening. Genes involved in starch and soluble sugar metabolisms displayed diverse expression profiles after MeJA treatment during ripening. Our data indicated that exogenous MeJA can alter apple quality by mediating carbohydrate metabolism.