Figure 11.

Proposed Models for Rice Flower Development.

(A) Roles of MADS6 and floral homeotic genes in specifying rice flower development. MADS6 specifies palea identity by repressing DL expression. It regulates lodicule development by activating the expression of SPW1 and MADS4 and physically interacting with the MADS4-SPW1 complex (Seok et al., 2010). MADS6 regulates the stamen, carpel, and meristem identities by activating the expression of MADS3 and MADS58 at early stages and specifies carpel/ovule development and controls floral meristem termination by interacting with MADS13 (Moon et al., 1999). MADS4 or MADS13 interacts with MADS7 and MADS8, respectively (Kater et al., 2006). In addition, MADS6 determines flower development redundantly with LHS1, MADS7, and MADS8 (Ohmori et al., 2009; Li et al., 2010). It also promotes the expression of MADS7 and MADS8 and physically interacts with MADS7 and MADS8 (Moon et al., 1999). Furthermore, MADS6, MADS3, MADS58, DL, and MADS13 redundantly specify floral meristem determinacy (Yamaguchi et al., 2004, 2006; Dreni et al., 2011; Li et al., 2011).

(B) ABCDE model in rice flower develoment. The putative A-class gene DEP defines palea identity (Wang et al., 2010; Li et al., 2011). The E-function genes LHS1, MADS6, and MADS34 specify lemma/palea identities. The A-class gene (DEP), B-class genes SPW1, MADS2, and MADS4, in combination with the E-class genes LHS1, MADS6, MADS7, MADS8, and MADS34, specify the lodicule identity. The B-class genes, the C-class genes MADS3 and MADS58, together with the E-class genes determine the stamen identity. DL specifies carpel identity. The D-class gene MADS13 and E-class genes determine carpel/ovule identity. Additionally, DL antagonistically regulates the expression of B-class genes, and the C-class gene MADS3 represses the expression of the putative A-class gene DEP (MADS15) (Li et al., 2011).

ca, carpel; le, lemma; lo, lodicule; ov, ovule; pa, palea; st, stamen.

[See online article for color version of this figure.]