De novo transcription of specific mRNAs during the induction of tobacco pollen embryogenesis

Abstract

An in vitro starvation treatment of isolated, immature Nicotiana tabacum L. pollen grains induces the formation of embryogenic cells that develop into embryos after transfer to a sugar-containing medium. Specific mRNAs which are not present in the young pollen grains before starvation were detected in embryogenic pollen by two-dimensional (2-D) gel electrophoresis of their in vitro-translated products. A similar analysis of in vivo-synthesized proteins, however, did not reveal new protein spots. These results indicate that starvation induces de novo transcription of specific genes, although the corresponding mRNAs may not be translated in vivo but accumulate in embryogenic pollen grains in a translationally inactive form. Changes in protein kinase activities were detected during the starvation treatment, suggesting that protein phosphorylation may also be involved in the process of embryogenic induction in pollen.