Localization of the Fe(III)-Zn(II) Purple Acid Phosphatase in Dry Kidney Beans Using Immunofluorescence and Immunogold Electron Microscopy

Abstract

Localization of purple acid phosphatase (PAP) from the seeds of kidney beans,Phaseolus vulgaris(L.), was performed using light and transmission electron microscopy. After rehydration and aqueous fixation, cryo-sections of bean cotyledon tissue showed a bright immunofluorescent signal in the cytoplasm of cells whereas cell walls and reserve materials (starch, protein bodies) remained unstained. In ultrathin sections of dry cotyledon tissue anhydrously fixed in acrolein vapour and embedded in Lowicryl resin, PAP mapped exclusively to ribosome-rich areas of the cytoplasm. In view of these results, we propose that kidney bean PAP might possibly be engaged in mechanisms involved in the triggering of seed dormancy.