Key aromatic amino acid players in soybean (Glycine max) genome under drought and salt stresses

Abstract

In this study chorismate synthase, chorismate mutase and anthranilate synthase in the soybean genome (GmCS, GmCM, and GmAS or collectively named as GmAAAs in this study), were investigated using bioinformatics and expression analyses under salt and drought stresses. It is found that there are multiple copies of GmCM, GmCS, and GmAS in the soybean genome due to dispersed duplication; therefore, dispersion of paralog GmAAAs may indicate functional diversification of GmAAAs in the soybean genome. GmCM1, GmAS2 and GmAS3 genes were expressed above 1.5-fold in the tolerant cultivar according to results of digital expression analyses, suggesting that these three genes in drought-tolerant variety may be part of the drought tolerance mechanism rendering the cultivar tolerant to drought. The co-expression analyses indicate that some of the drought-regulated genes participate in the salinity stress response mechanism as well. The foliar gene expression analyses of selected GmAAAs showed that the highest gene expression under salt stress was in GmCM5 with 1.79-fold at 50 and 200 mM NaCl concentrations. Similarly, the highest upregulation of GmAAAs under drought stress was in GmCM5 with 2.23-fold. Generally, drought stress induced higher expressions of GmAAAs compared to salt stress in this study. Although the expression of aromatic amino acid genes differs depending on the duration of exposure to stress, plant organs and the type of abiotic stress; CM proteins may be one of the key players under both salt and drought stresses when the importance of AAA genes is considered. By and large, the findings presented in this study will enlighten the AAA pathway in plants, particularly in soybean.