Assessing α-galactosidase OmAGAL2 inhibitors and their impact on germination and sugar profiles in <i>Orobanche minor</i>

Root parasitic weeds from the <i>Orobanche</i> genus significantly damage crop production in African and European countries. Previous studies identified the metabolism of planteose, a storage trisaccharide in root parasitic weeds, as a potential control target. In <i>Orobanche minor</i>, α-galactosidase OmAGAL2 hydrolyzes planteose into sucrose upon perceiving germination stimulant strigolactones. Subsequently, invertases break down sucrose into glucose and fructose, essential for germination. This study screened chemical libraries to identify inhibitors against OmAGAL2-mCherry, secreted from transgenic tobacco BY-2 cells. Two inhibitors, 82-G8 and 85-B10, which significantly reduced the OmAGAL2 activity to less than 70% of the control, were evaluated for their impact on <i>O. minor</i> germination and sugar profiles. Results showed that OmAGAL2 inhibitors suppressed <i>O. minor</i> radicle elongation by inhibiting planteose metabolism, with effects more pronounced when applied at the start of conditioning rather than during germination stimulation. Further structural optimization could yield a novel class of chemicals for controlling <i>Orobanche</i> spp.