“…Homologous bHLH proteins in animals, such as the four mammalian myogenic regulators, MyoD, Myf-5, myogenin, and MRF4, as well as the achaete-scute complex in Drosophila melanogaster, control sequential processes in a hierarchical fashion (Olson, 1990;Campuzano and Modolell, 1992;Weintraub, 1993). In Arabidopsis, three closely related bHLH proteins, SPCH, MUTE, and FAMA, are key switches for three key consecutive steps of stomatal formation (Ohashi-Ito and Bergmann, 2006;MacAlister et al, 2007;Pillitteri et al, 2007;Lampard, 2009;Hachez et al, 2011;Triviño et al, 2013) Our previous work shows that, phylogenetically, TIP2, EAT1, and TDR are closely grouped (X. , and they might be generated by gene duplication during evolution. This work and our previous discovery reveal that these three bHLH proteins display successive expression patterns and have overlapping and divergent functions during anther development (Figure 10) (N. Niu et al, 2013).…”