Aluminum-Specific Upregulation of GmALS3 in the Shoots of Soybeans: A Potential Biomarker for Managing Soybean Production in Acidic Soil Regions

Aluminum (Al) toxicity in acidic soils is a global agricultural problem that limits crop productivity through the inhibition of root growth. However, poor management associated with the application of soil acidity amendments such as lime (CaCO3) in certain crop types can pose a threat to low-input farming practices. Accordingly, it is important to develop appropriate techniques for the management of crop production in acidic soils. In this study, we identified ALS3 (ALUMINUM SENSITIVE 3) in soybeans (Glycine max, cultivar Toyomasari), which is highly expressed in the shoot under Al stress. GmALS3 (Glyma.10G047100) expression was found to be Al-specific under various stress conditions. We analyzed GmALS3 expression in the shoots of soybean plants grown in two different types of acidic soils (artificial and natural acidic soil) with different levels of liming and found that GmALS3 expression was suppressed with levels of liming that have been shown to eliminate soil Al3+ toxicity. Using soybeans as a model, we identified a potential biomarker that could indicate Al toxicity and appropriate liming levels for soybeans cultivated in acidic soils.