Localization of planteose hydrolysis during seed germination of Orobanche minor

Abstract

Root parasitic weeds of the Orobanchaceae, such as witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.), cause serious losses in agriculture worldwide. No practical method to control these parasitic weeds has been developed to date. Understanding the characteristic physiological processes in the life cycles of root parasitic weeds is particularly important to identify specific targets for growth modulators. In our previous study, planteose metabolism was revealed to be activated soon after the perception of strigolactones in germinating seeds of O. minor. Nojirimycin inhibited planteose metabolism and impeded seed germination of O. minor, indicating that planteose metabolism is a possible target for root parasitic weed control. In the present study, we investigated the distribution of planteose in dry seeds of O. minor by matrix-assisted laser desorption/ionization-mass spectrometry imaging. Planteose was detected in tissues surrounding--but not within--the embryo, supporting its suggested role as a storage carbohydrate. Biochemical assays and molecular characterization of an -galactosidase family member, OmAGAL2, indicated the enzyme is involved in planteose hydrolysis in the apoplast around the embryo after the perception of strigolactones to provide the embryo with essential hexoses for germination. These results indicated that OmAGAL2 is a potential molecular target for root parasitic weed control. HighlightPlanteose accumulated in tissues surrounding the embryo in Orobanche minor dry seeds and was indicated to be hydrolyzed in the apoplast around the embryo by -galactosidase during germination.