Figure 8.

A working model summarizing the roles of homeotic MADS-box genes during rice spikelet development. A, The expression domains of A-, B-, C-, D-, and E-class and AGL6-like genes in different spikelet organs. During the spikelet development, the expression of the FUL1-like gene OsMADS14 is found in the SM; later restricted to the sterile lemmas, lemma, and palea (Pelucchi et al., 2002; Preston and Kellogg, 2006, 2007); and the FUL2-like gene OsMADS15 is also expressed in the SM and continues in the sterile lemmas, lemma, palea, and lodicules (Kyozuka et al., 2000; Preston and Kellogg, 2006, 2007). The PI/GLO-like genes OsMADS2 and OsMADS4 and the AP3/DEF-like gene OsMADS16 share a common conserved expression domain in the lodicule and stamen primordia (Nagasawa et al., 2003; Yadav et al., 2007; Yun et al., 2013). In general, the AG lineage genes OsMADS3 and OsMADS58 exhibit a very similar expression profile in the stamen, carpel, and ovule primordia (Dreni et al., 2011). The expression of the AGL11 lineage gene OsMADS13 is specific in the ovule primordium (Lopez-Dee et al., 1999; Dreni et al., 2011), and yet the other AGL11 lineage gene OsMADS21 is expressed in the developing ovule integument and very weakly in stamens and carpels (Arora et al., 2007; Dreni et al., 2007; Dreni et al., 2011). The two AGL6-like genes OsMADS6 and OsMADS17 show a largely overlapping expression patterns in the FM and, later, in palea, lodicule, and ovule (Favaro et al., 2002; Pelucchi et al., 2002; Ohmori et al., 2009; Li et al., 2010). B, Genetic and physical interactions of MADS-box factors in regulating rice spikelet morphogenesis. Black arrows indicate the interactions presented in this study and gray arrows show the interactions reported in previous works (see manuscript text for references). Bop, body of palea; Ca, carpel; FD, floral meristem determinacy; Le, lemma; Lo, lodicule; Mrp, marginal region of palea; OsM, OsMADS; Ov, ovule; Pa, palea; Pi, pistil; Rg, rudimentary glume; Sl, sterile lemma; St, stamen.