H3.3 is abundantly expressed in anther and regulates microgametogenesis. (A) Schematic representation of the pH3.3-H3.3-GUS constructs, including pHTR4-HTR4-GUS, pHTR5-HTR5-GUS and pHTR8-HTR8-GUS. (B) Histochemical localization of HTR4-GUS, HTR5-GUS and HTR8-GUS activities in transgenic plants. Top, 5-day-old seedlings; middle, inflorescences; bottom, flowers. Scale bars, 1 mm. (C) Transverse sections of anther lobes in pHTR4-HTR4-GUS, pHTR5-HTR5-GUS and pHTR8-HTR8-GUS transgenic plants indicated in Fig. 3B. Scale bars, 50 μm. (D) Transverse sections of Col-0 and h3.3–1 anther lobes at stage 7 and stage 11. Scale bars, 50 μm.