Fig. 5. HAP2 expression is sperm specific. (A) RT-PCR of wild-type tissues, using primers spanning HAP2 exon 2 (25-40 cycles). (B) Northern blot of wild-type RNA probed with full-length HAP2 cDNA; ethidium bromide stained gel before blotting shows relative RNA amounts in each lane. The source of each RNA sample is indicated between A and B. (C) A pollen tetrad from a plant heterozygous for the HAP2promoter:YFP fusion; DAPI fluorescence (left), YFP fluorescence (center), merged image (right). (D) DAPI (left) and YFP (right) fluorescence in pollen tetrads from qrt and homozygous HAP2promoter:YFP transgenic plants. Uninucleate microspores (UNM, left panels), bicellular pollen (BCP, center panels) and mature pollen grains (right panels) were analyzed. Autofluorescence from the pollen surface is observed in wild-type and transgenic pollen; signal from YFP is only observed in the sperm of mature pollen grains from transgenic plants. Scale bars: 20 µm.