Abstract

It is well documented that aluminum (Al) toxicity is the most important constraint of crop production on acid soils. Chelation of Al in the rhizosphere with root secreted organic acid anions is a common mechanism of Al tolerance in most plants including soybean. Phenolic substances are recently implicated as additional physiological mechanism of plant Al tolerance. This study was undertaken to investigate the role of phenolics in soybean Al tolerance and to examine protein expression changes in soybean roots under Al stress. An Al-tolerant soybean genotype PI 416937 and Al-sensitive Young were used in the study. Protein and polyphenol profile changes in response to Al stress, were examined in roots tips of hydroponically grown plants 72 h post treatment. Al significantly increased total phenol exudation from roots of the Al tolerant genotype PI 416937, whereas, flavonoid content did not vary with treatment. Al also altered the expression level of several proteins in genotypic and non genotypic specific manner. This is the first study to show that polyphenol is involved in soybean Al tolerance. Future research should consider quantification of individual flavonoid compounds in root tissue as well as culture solution, and sequencing and functional annotation of Al regulated proteins.

Key words: Soybean, aluminum tolerance, protein expression, phenolics.