3-Methyladenine and lithium chloride treatment regulate longan pulp breakdown via adjusting the metabolisms of energy and respiration

This work investigated the impacts of the autophagy inhibitor 3-methyladenine (3-MA) and autophagy activator lithium chloride (LiCl) treatment on pulp breakdown in postharvest longan by analyzing energy and respiration metabolisms. The outcomes demonstrated that, compared to the control (CK) fruit, 3-MA treatment aggravated pulp breakdown and decreased autophagy activity. This was accompanied by lower values of ATP, ADP, and energy charge, and lower activities of H + -ATPase, Ca 2+ -ATPase, and Mg 2+ -ATPase, despite an increase in AMP content. Furthermore, the 3-MA-treated longans showed a higher respiration rate, and higher PGI, SDH, AOX, and CCO activities, along with higher QH 2 and NAD(H) levels; conversely, levels of 6-PGDH, G-6-PDH, NADK, Q, and NADP(H) were lower. However, the LiCl-treated longans exhibited opposite effects. These findings suggested that 3-MA treatment-accelerated longan pulp breakdown was due to 3-MA reducing the levels of autophagy and energy status, enhancing the levels of EMP, TCA cycle, electron transport chain, and respiratory intensity, and lowering pentose phosphate pathway. In contrast, LiCl treatment-retarded longan pulp breakdown was owing to LiCl inducing higher levels of autophagy and energy status, lowering the levels of EMP, TCA cycle, electron transport chain and respiratory intensity, and activating pentose phosphate pathway.