Arabinogalactan proteins: Immunolocalization in the developing ovary of a facultative apomict Fragaria x ananassa (Duch.)

Abstract

Background and aimsArabinogalactan proteins are present in the extracellular matrix and their occurrence is developmentally regulated. The studies were carried out to localise arabinogalactan proteins in ovary cells of Fragaria x ananassa Duchesne (strawberry) during megasporogenesis, megagametogenesis, and formation of the embryo. MethodsThe research included studies of ovary histochemistry and immunofluorescence labelling of AGP epitopes was performed with antibodies JIM13, JIM15 and MAC207. The use of the immunogold labelling method allowed specific detection of AGP epitopes at the subcellular level. Key resultsThe localization of AGPs was studied in the cells of the ovary wall and elements building the developing ovule i.e. the integument, nucellus, archespore, megaspores, embryo sac, and embryo of a facultative apomict Fragaria x ananassa cv. 'Mount Everest'. For the first time the presence of AGP epitopes at the stage of a multicellular archespore was described. The occurrence of AGPs in the functional megaspore walls is related to selection of a megaspore continuing development; during later stages of development, AGPs are also evident markers of the female gametophyte. The intense fluorescence indicates the presence of AGPs in the embryo sac wall as well as in the cytoplasm compartment of the egg apparatus and around the secondary nucleus of the central cell. The localization of AGPs in the ovule of F. x ananassa resembles the distribution of these proteins in amphimictic plants. ConclusionsArabinogalactan proteins occur in similar parts of the ovule of amphimictic and apomictic plants. The results confirm the participation of AGPs in reproductive structures as a useful marker during development of female gametophyte.