Expansins are plant cell wall loosening proteins that are involved in cell enlargement and a variety of other developmental processes. The expansin superfamily contains four subfamilies; namely, α-expansin (EXPA), β-expansin (EXPB), expansin-like A (EXLA), and expansin-like B (EXLB). | Soybean Glycine max expansin gene superfamily origins Segmental and tandem duplication events followed by divergent selection among subfamilies