Citrate transporters play an important role in regulating aluminum-induced citrate secretion in Glycine max

To further understand the process of Al-induced citrate secretion from soybean roots, the effect of protein synthesis inhibitor, anion channel blockers, and citrate carrier inhibitors on Al-induced citrate exudation was investigated in Al-resistant soybean cultivar PI 416937. Citrate exudation from roots increased with the increase of Al concentration from 10 to 50 mu M and initiated after 4 h of Al exposure. Protein synthesis inhibitor, cycloheximide (CHM; 25 mu M) completely inhibited Al-induced citrate secretion during 12-h exposure, suggesting that novel protein synthesis was necessary in Al-induced citrate efflux. Also both anion channel blocker anthracene-9-carboxylic acid (A-9-C) and citrate carrier inhibitor mersalyl acid (Mersalyl) significantly reduced citrate secretion, suggesting that both anion channels in plasma membrane and citrate carriers in mitochondria membrane were the rate limiting factors of Al dependent citrate release. However, Al-induced citrate secretion was insensitive to anion channel blockers phenylglyoxal (PG), 4,4'-diisothiocyanostibene-2,2'-disulfonat (DIDS) and citrate carrier inhibitor pyridoxal 5'-P (PP).