bearded-earEncodes a MADS Box Transcription Factor Critical for Maize Floral Development  

Abstract

Although many genes that regulate floral development have been identified in Arabidopsis thaliana, relatively few are known in the grasses. In normal maize (Zea mays), each spikelet produces an upper and lower floral meristem, which initiate floral organs in a defined phyllotaxy before being consumed in the production of an ovule. The bearded-ear (bde) mutation affects floral development differently in the upper and lower meristem. The upper floral meristem initiates extra floral organs that are often mosaic or fused, while the lower floral meristem initiates additional floral meristems. We cloned bde by positional cloning and found that it encodes zea agamous3 (zag3), a MADS box transcription factor in the conserved AGAMOUS-LIKE6 clade. Mutants in the maize homolog of AGAMOUS, zag1, have a subset of bde floral defects. bde zag1 double mutants have a severe ear phenotype, not observed in either single mutant, in which floral meristems are converted to branch-like meristems, indicating that bde and zag1 redundantly promote floral meristem identity. In addition, BDE and ZAG1 physically interact. We propose a model in which BDE functions in at least three distinct complexes to regulate floral development in the maize ear.

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

“…Furthermore, OsMAS6 is able to form protein complexes with rice B and D proteins in yeast cells [47,48], resembling the complex formation of SEP proteins with A, B and C in Arabidopsis and other eudicot species [9,54]. Moreover, a physical interaction between BDE and ZAG1 (Zea AGAMOUS 1, a C class protein) in maize has also been shown recently [40].…”

“…The monocotyledonous species maize has two AGL6-like genes, ZAG3 and ZAG5 [39]. 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].…”

“…Furthermore, a maize AGL6-like gene bearded-ear (bde) has been recently shown to play pleiotropic roles in controlling floral meristem determinacy, organ specification and sex determination [40]. The bde mutant displays abnormal floral development; extra floral mosaic organs are observed in the upper floral meristem, but the lower part develops additional floral meristems [40].…”

Evolution ofAGL6-likeMADS Box Genes in Grasses (Poaceae): Ovule Expression Is Ancient and Palea Expression Is New

“…In maize (Zea mays) two AGL6-like genes, zag3 and zag5, have been characterized (Mena et al, 1995). zag3 mRNA in situ hybridization showed that it is expressed in both upper and lower floral meristems but not in the lemma and stamens (Thompson et al, 2009). Later in development, zag3 is expressed in developing lodicules, palea, carpels, and the inner integument.…”

“…Later in development, zag3 is expressed in developing lodicules, palea, carpels, and the inner integument. Characterization of a zag3 mutant, the only loss-of-function mutant available for an AGL6-like gene, demonstrates a role in floral meristem and organ development (Thompson et al, 2009). No data are available on the specific floral organs where zag5 is expressed.…”