Pollen phenotype of <i>fbl17</i> mutants and <i>FBL17</i> expression during male gametogenesis.

<p><i>fbl17</i> (A) and wild type (B) mature pollen viability test by coloration with Alexander's stain. The purple staining indicates that the grains are viable. Dehiscent pollen of <i>qrt1-1^−/−</i> (C) and <i>qrt1-1^−/−</i>, <i>fbl17-1^+/−</i> (D) stained with DAPI and observed under UV fluorescence. The four pollen grains of the tetrad show two densely stained sperm cell nuclei and one large diffuse vegetative cell nuclei in <i>qrt-1</i> mutants, whereas two pollen grains of the tetrad show only a single germ cell nuclei in <i>qrt1-1,fbl17-1^+/−</i> double mutants. (E, F) transmitted light picture of C and D. (G–L) Expression of the <i>HT10</i> gene in the <i>fbl17</i> mutant pollen. Expression of the HTR10-mRFPprotein under the HTR10 promoter in <i>fbl17-1</i> (H) and wild type (K) pollen, counterstained with DAPI (G, <i>fbl17-1</i>; J, wild type). (I, L) transmitted light pictures of G and J. (A, B) bar = 100 µm; (C–L) bar = 10 µm. (M–U) Promoter-GUS analysis of <i>FBL17</i> expression in pollen. (M, P, S) DAPI staining is applied to reveal the developmental stage of the pollen grain. (N–U) X-Gluc histochemical staining of pFBL17∶GUS (N, Q, F) and non-transformed Col-0 (O, R, U) pollen grains. Bars = 10 µm (V) DNA content measurement of wild type germinative cell nuclei at prophase (n = 9; DNA = 2C), wild type sperm cell nuclei at telophase (n = 16), WT sperm cell nuclei at anthesis (n = 111) in comparison to the unique germ-cell like nuclei of <i>fbl17</i> pollen (n = 77). Error bars = standard error mean.