Green sperm. Identification of male gamete promoters in Arabidopsis.

Previously, in an effort to better understand the male contribution to fertilization, we completed a maize (Zea mays) sperm expressed sequence tag project. Here, we used this resource to identify promoters that would direct gene expression in sperm cells. We used reverse transcription-polymerase chain reaction to identify probable sperm-specific transcripts in maize and then identified their best sequence matches in the Arabidopsis (Arabidopsis thaliana) genome.

Sperm cells of Zea mays have a complex complement of mRNAs.

Although double fertilization in angiosperm was discovered in 1898, we still know nothing about the proteins that mediate gamete recognition and fusion in plants. Because sperm are small and embedded within the large vegetative cell of the pollen grain, mRNAs from sperm are poorly represented in EST databases. We optimized fluorescence-activated cell sorting (FACS) in order to isolate Zea mays sperm free of contaminating vegetative cell cytoplasm, and constructed a cDNA library.