A characterization of the MADS‐box gene family in maize

Abstract

Studies on distantly related dicot plant species have identified homeotic genes that specify floral meristem identity and determine the fate of floral organ primordia. Most of these genes belong to a family characterized by the presence of a structural motif, the MADS-box, which encodes a protein domain with DNA-binding properties. As part of an effort to understand how such genes may have been recruited during the evolution of flowers with different organ types such as those found in maize, two members of this gene family in maize, ZAG1 and ZAG2, have been characterized previously. Here, the isolation and characterization of four new members of this gene family, designated ZAP1, ZAG3, ZAG4 and ZAG5, are described and the genetic map position of these and 28 additional maize MADS-box genes is determined. The first new member of this family appears to be the Zea mays ortholog of the floral homeotic gene APETALA1 (AP1) and has been designated ZAP1. One of these genes, ZAG4, is unusual in that its deduced protein sequence includes the MADS domain but lacks the K-domain characteristically present in this family of genes. In addition, its copy number and expression varies among different inbreds. A large number of maize MADS-box genes map to duplicated regions of the genome, including one pair characterized here, ZAG3 and ZAG5. These data underscore the complexity of this gene family in maize, and provide the basis for further studies into the regulation of floral organ morphogenesis among the grasses.

The whorl‐specific action of a petunia class B floral homeotic gene

“…7c) (van der Krol et al 1993). This is similar to the ZAG3 expression in tassels and ears (Mena et al 1995). In the bl, gp and bl gp mutant¯owers, pMADS4 was expressed strongly in the organs of the ®rst, second and fourth whorls, but very weakly in organs of the third whorl, as in the wildtype¯ower (Fig.…”

The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice

“…ZAG3 was expressed in both male and female maize inflorescences [40]. Its expression was found in carpels, but not in stamens, and in the sterile floral organs, but not in glumes [39]. The expression of Gnetum GGM9 and GGM11 genes was observed in male and female reproductive cones, but not in vegetative leaves [41].…”

“…The transcripts of AGL6 were detectable in all four whorls of floral organs [37], whereas AGL13 was expressed in ovules [38]. The monocotyledonous species maize has two AGL6-like genes, ZAG3 and ZAG5 [39]. ZAG3 was expressed in both male and female maize inflorescences [40].…”

Markers and mapping: we are all geneticists now

“…To screen a population for individuals producing a particular one of the isoenzyme forms, it will be necessary to obtain the right pair of markers each of which is linked to the right allele at one of the two discrete loci encoding the enzyme subunits. Another well characterized example of interacting but often unlinked loci is the group of genes known as homeotic, whose products determine the form of plant organs such as flowers (see, for example, Mena et al, 1995). Expression of two or more homeotic genes in the right cells at the right time is essential for normal flower development ; knocking out one gene has a different effect from knocking out another.…”