Salicylic acid involved in the process of aluminum induced citrate exudation in Glycine max L

Background and aims Aluminum (A1)-induced citrate exudation has been identified as an important A1-resistance mechanism in soybean. Salicylic acid (SA) is a crucial signal molecule modulating numerous environment stresses in plants. This study was to investigate the role of SA in A1-induced citrate exudation from soybean roots. Methods HPLC was used to test the A1-induced endogenous SA changes, effect of exogenous SA / an inhibitor of SA biosynthesis paclobutrazol (PAC) on A1-induced citrate efflux. The activity / transcriptional expression of mitochondrial aconitase (ACO) and a putative citrate transporter gene Gm-MATE1 were examined by an enzyme method or qRT-PCR. Results A1 stress caused increase of endogenous free-SA and conjugated SA (SAG). Exogenous SA enhanced the amount of A1-induced citrate secretion from roots, decreased the A1 accumulation in root apices and alleviated the A1-induced inhibition of root elongation. PAC decreased the A1-induced enhancement of endogenous free SA and reduced the amount of citrate exudation. SA and A1 together treatment further decreased mitochondrial aconitase (ACO) activity and enhanced the transcriptional expression of Gm-MATE1 compared to the sole A1 treatment. Conclusions A1-induced SA production may act as an early signal to regulate the metabolism and transportation of citrate in soybean roots.