Analysis of gene expression in microspores, pollen, and silks of Zea mays L.

Abstract

During pollen formation within anthers of Zea mays, post-meiotic expression of the cat-3 gene was observed from soon after microspore release from the tetrads until microspore mitosis; from the binucleate stage to maturity the cat-1 gene was expressed instead. Gene expression during pollen function, i.e., germination and tube growth, was determined by means of a new approach based on the in vivo comparative analysis of pollinated and non-pollinated silks. In the early autotrophic stage of germinating pollen ADH-1, CAT-1, and GOT-1 were expressed, whereas during further tube elongation only GOT-1 was detected. Pollination did not give rise to pollen-style hybrid enzymatic molecules nor to the induction of new enzymes on either partner. Silks, even when non-pollinated, showed the expression of additional alcohol dehydrogenase and catalase enzymatic activities, specifically ADH-2 and CAT-3. These data support the view that expression of the catalase system in the male gametophyte is stage specific, and suggest that the style may provide support to the elongating pollen tube at the functional as well as at the nutritional level.