Visualization of starch-synthase expression by in situ hybridization during pollen development.

The expression of the starch-synthase gene was studied by in situ RNA hybridization at different stages of pollen development in tobacco (Nicotiana tabacum L.). By means of Northern blot analysis we demonstrated that a potato (Solarium tuberosum L.) gene was homologous to its tobacco counterpart, and then we synthesized (35)S-labeled RNA probes from this gene. The probe was seen to bind at the tetrad stage. Unicellular pollen grains showed no starch-synthase mRNA but these transcripts reappeared in the binucleate stages, being abundant in mature pollen grains. Our results show that starch-synthase is expressed in the gametophytic cells. Variations in mRNA accumulation during the different stages indicate a regulation of this gene throughout pollen development.