Al-enhanced Expression and Interaction of 14-3-3 Protein and Plasma Membrane H+-ATPase is Related to Al-induced Citrate Secretion in an Al-resistant Black Soybean

Abstract

The up-regulated expression of plasma membrane (PM) H+-ATPase is related to Al-enhanced citrate exudation in soybean. Moreover, the interaction with a 14-3-3 protein can activate PM H+-ATPase. This study investigated if the expression and interaction level of the 14-3-3 protein and PM H+-ATPase is associated with PM H+-ATPase activity as well as citrate secretion in Al-tolerant (RB) and Al-sensitive (SB) black soybeans, respectively, under 50 mM Al stress. The results showed that Al stress significantly induced transcription of the 14-3-3a gene in RB but not in SB roots. The Al-enhanced transcription of the PM H+-ATPase encoding gene (gha2) was higher in RB than in SB roots. The translation and phosphorylation of PM H+-ATPase, the interaction between the 14-3-3 protein and the phosphorylated PM H+-ATPase all showed an increasing pattern in RB but displayed a descending pattern in SB during the whole Al stress period. Consistently, H+ pump activity and citrate secretion were also higher in RB than in SB under Al stress. Furthermore, citrate secretion was correlated positively with PM H+-ATPase activity in RB and SB under Al stress. These results indicated that Al-enhanced expression of 14-3-3 protein and PM H+-ATPase and the interaction between 14-3-3 protein and phosphorylated PM H+-ATPase increased the activity of PM H+-ATPase and the H+ pump, thereby augmenting citrate secretion in RB. This might be an important molecular mechanism underlying the higher Al-tolerance in RB compared to SB.