Fig. 8

Evolution of PHO1-like genes during the speciation of soybeans. a Molecular evolution of soybean PHO1 genes. The sequence evolution of the soybean PHO1 gene family was conceptualized referred by the phylogenetic trees of this gene family (this work; [45]). b, c Expressional diversification of soybean PHO1 genes and functional diversification. The transcript sequence and expression of Class I genes in gray (in a) were not detected, thereby suggesting pseudogenization. The expression pattern in response to the indicated stresses is summarized in roots of SN14 and ZYD6 (b), whereas the tissue-specific expression patterns of this gene family were inferred from the data from all accessions of G. soja and G. max that were used in this work (c). The response of each gene to the stresses. The box in red, blue, and white respectively indicate upregulated, downregulated, and unchanged expression in response to the indicated stresses. Overall, four patterns of gene expression variation were defined under salinity stresses (S1-S4), and low-Pi conditions (P1-P4) among wild and cultivated soybeans (for details, see Additional file 2: Table S6). Gm, G. max; Gs, G. soja. The function of soybean PHO1 genes was inferred from transgenic Arabidopsis indicated by a star (*). The PHO1 functions from model plants Arabidopsis thaliana and rice were included to endorse the diverse roles and functional divergence of Classes I and II in the PHO1 gene family