Analysis of the expression pattern of BcMF9 in Chinese cabbage using in situ hybridization. (A − F) Sections of anthers at the pollen mother cell, meiosis, tetrads, uninucleate, binucleate and mature pollen stage, respectively, hybridized with a BcMF9 antisense probe. (G − L) Section of anthers at the pollen mother cell, meiosis, tetrads, uninucleate, binucleate and mature pollen stage, respectively, hybridized with a BcMF9 sense probe as a negative control. Abbreviations: Bp, binucleate pollen; Mp, mature pollen; Ms, microspore; PME, pollen mother cell; Te, tetrad; T, tapetum; Up, uninucleate pollen. Scale bars = 20 µm.