Precursor genes of Bowman-Birk-type serine proteinase inhibitors comprise multiple inhibitory domains to promote diversity

•Herein, Hyacinthus orientalis serine protease inhibitors (HOSPIs) were evaluated.•HOSPI precursors have coding regions that contain 4–2 different inhibitory domains.•Additional head, linker, and tail sequences connect these HOSPI domains.•Introns may occur between the linkers, introducing alternative splicing sites to HOSPI.•These findings shed light into the diversity of protease inhibitors diversity.