Half of the pollen population from the plants expressing the β-glucosidase was found to be sterile. The pollen development was divided into six development stages/phases which correlated with distinct cytological characteristics. On the basis of microscopic and histochemical studies, using X-glc (5-Bromo-4-chloro-3-indolyl-β-D-glycopyranoside) as substrate, β-glucosidase activity was found in half the pollen of the transgenic tobacco plants. The dynamics of starch metabolism in the developing pollen of positive plants (i.e. plants expressing Zm-p60.1 in the leaf) in comparison to that of the negative plants (i.e. plants not expressing Zm-p60.1 in the leaf), was studied in order to elucidate the possible role of Zm-p60.1 in starch metabolism. Detection of the β-glucosidase (Zm-p60.1) was achieved using β-glucosidase histochemical and biochemical assays. The activities of selected enzymes of sucrose metabolism (UDPG-pyrophosphorylase) and starch metabolism (ADPG-pyrophosphorylase, starch-phosphorylase, and amylase) were biochemically analyzed. Histochemical studies with potassium iodide revealed that 50% of the pollen of the positive plants (i.e. tobacco plants expressing β-glucosidase activity) exhibited normal starch accumulation. Biochemical determination of starch revealed that the pollen expressing Zm-p60.1 contained significantly lower amount of starch in comparison to the pollen from negative plants (i.e. tobacco plants not expressing β-glucosidase activity). About 50% of the pollen population expressing Zmp-60.1 has decreased starch content. The same starchless pollen exhibited β-glucosidase activity.
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