The Role of MADS-Box Genes in the Control of Flower and Fruit Development in Arabidopsis

Abstract

Arabidopsis flowers and fruit are typical of the more than three thousand species of Brassicaceae and have been the subject of intensive genetic and molecular studies. Among the many genes that have been identified that control various aspects of flower and fruit development, the MADS-box family has been shown to play central roles. MADS-box genes encode putative transcriptional regulators that play regulatory roles not only in diverse plant species, but also in fungal and animal development. The first Arabidopsis MADS-box gene to be cloned was AGAMOUS in 1990, and in the ensuing years, dozens of related genes have been cloned and functionally characterized (Yanofsky et al., 1990; Riechmann and Meyerowitz, 1997; Theissen, 2000). Three general lessons have been learned from these functional studies. The first, is that MADS-box genes play diverse roles in plant development, ranging from the control of flowering time, meristem identity, organ identity, fruit development, and they also appear to play roles during embryo, ovule, seed, root, stem and leaf development. A second lesson that we have learned is that MADS-box genes frequently play multiple roles during development. For example, the FRUITFULL gene is involved in leaf development as well as in fruit development. A third lesson is that functional redundancy is prevalent among MADS-box genes. In some cases, single mutants are indistinguishable from the wild type, whereas double mutants carrying mutations in two closely related MADS-box genes display striking phenotypic abnormalities. In this manuscript, we will focus on recent examples from our laboratory that highlight these three basic conclusions of MADS-box gene function.