Adenosine 5′-monophosphate decreases citrate exudation and aluminium resistance in Tamba black soybean by inhibiting the interaction between 14-3-3 proteins and plasma membrane H+-ATPase

Our previous study suggested that aluminium (Al) stress increased plasma membrane (PM) H+-ATPase activity and citrate secretion and simultaneously enhanced the interaction between 14-3-3 proteins and phosphorylated PM H+-ATPase in Al-resistant Tamba black soybean (RB). Adenosine 5′-monophosphate (AMP) is known as an inhibitor of the interaction between 14-3-3 proteins and PM H+-ATPases. To investigate the effects of AMP on Al resistance, PM H+-ATPase activity and citrate exudation, AMP was used to treat Al-stressed RB. The results showed that after treatment with either 100 μM AMP or 50 μM Al for 8 h, RB root growth was inhibited by approximately 50 and 30%, respectively. However, simultaneous treatment with 100 μM AMP and 50 μM Al for 8 h resulted in a 60% inhibition of RB root growth, indicating that the presence of AMP reduced Al tolerance in RB. The interaction of PM H+-ATPase and 14-3-3 proteins in the root tips of Al-treated RB was stronger than that in the untreated control. However, the interaction of the two proteins was greatly reduced (lower than that in the control) after co-treatment with Al and AMP, suggesting that the presence of AMP under Al stress reduced the Al-enhanced interaction between PM H+-ATPase and 14-3-3 proteins. Consequently, PM H+-ATPase activity decreased by approximately 50%, which led to a significant decrease in H+ efflux and citrate secretion in RB roots under Al stress. Collectively, these results indicate that AMP reduced citrate exudation and Al resistance in RB by inhibiting the interaction between 14-3-3 proteins and PM H+-ATPases under Al stress.