Figure 2. Nexine and intine layers are absent in tek (a–n).

TEM images of pollen wall development in wild type (a–f) and tek (h–m) from stage 7–12. (a,h) Later stage 7, showing the osmiophilic materials is reduced in tek; (b,i), stage 8, showing the nexine layer is absent in tek; (c,j), stage 9; (d,k), stage 10, showing the intine commenced in wild type; (e,l), stage 11, showing the degenerated tek pollen grain; (f,m), stage 12, showing the sexine and material analogues of intine still visible in tek. Scale bars, 500 nm (a–c and h–j); scale bars, 2 μm (d–f and k–m). Scanning electron microscopy of pollen grain of wild-type (g) and tek (n) showed the similar reticulate pattern. Scale bars, 5 μm. (o) AtUSP had its similar expression pattern in wild-type and tek anthers. Scale bars, 20 μm. (p) Cytochemical staining of semi-thin sections of wild-type, atusp/+ and tek. All wild-type pollens showed a pink fluorescent ring of the intine layer, while the half pollens of atusp/+ showed the absence of intine layer. A dim blue fluorescent ring was detected in the degraded pollen of tek. aIn, abnormal intine; Ca, callose wall; DPG, degenerated pollen grain; In, intine; In?, intine-like materials; MMC, microspores mother cell; MSp, microspore; Ne, nexine; PC, pollen coat; Pe, primexine; PG, pollen grain; PM, plasma membrane; Ps, pro-sexine; Se, sexine; T, tapetum; Tds, tetrads.