Flower and fruit development in Arabidopsis thaliana

Abstract

KEY WORDS: Arabidopsis, flower development, fruit patterning An introduction to flower developmentAngiosperms, the flowering plants, develop complex reproductive structures, the flowers. In spite of the great diversity in the form, color and structure of the flowers, they share a common characteristic, the basic construction plan. Most flowers consist of rings of floral organs, with external sterile organs surrounding the reproductive structures located in the center. A typical eudicot flower is composed of four rings, or whorls, of organs. The outermost whorl is composed of sepals and within this whorl are the petals, then the stamens (the male reproductive organs) and finally the carpels or female structures in the center of the flower (Figure 1). Later on in development, the fertilized carpels will give rise to the fruit.The last 15 years have been very fruitful for the study of the flower development and we now understand better how a flower develops. Most of the genetic and molecular studies that have played a key role in this understanding of flower development have been performed in three distant eudicot plants, Arabidopsis thaliana, Antirrhinum majus and Petunia hybrida. These studies, in conjunction with the initial cloning of some of the genes involved in flower development, led to the proposal of the elegant and broadly Int. J. Dev. Biol. 49: 633-643 (2005) doi: 10.1387/ijdb.052020pr accepted ABC model of flower development (Bowman et al., 1991, Coen and. Because this model proved valid for several other plant species (Rutledge et al., 1998, Tandre et al., 1998, Ambrose et al., 2000, Fornara et al., 2003 we can consider this ABC model as universal. However, it is during the last five years that new data have led to the proposal of a revised version of the classic ABC model, broadly accepted as the floral quartet model. The revised model includes a new function that is required for the development of the four types of floral organs and proposes that the development of each organ is achieved by the formation of large protein complexes. The ABC modelGenetic studies in Arabidopsis thaliana and Antirrhinum majus led to the proposal of the landmark ABC model of flower development (Bowman et al., 1991, Coen and. This model proposes that three different activities, A, B and C, alone or in combination specify the distinct organs of the four whorls of the flower. A function alone is responsible of the sepal development in the outermost whorl, A and B functions together specify the petals 634 P. Robles and S. Pelaz in the second whorl, B and C determine the stamens in the third whorl and C function specifies the carpels in the center of the flower. The model also proposes that A and C functions are mutually antagonistic (Figure 1). According to the model, mutant flowers in the A function genes have the sepals transformed into carpels and the petals into stamens due to the ectopic C activity in the outer whorls of the flower. The resultant flower is composed of carpels-stamens-stamens-carpels, from the out...

Genetic analysis of reproductive development in tomato

“…Such function is carried out by the E-class SEPALLATA (SEP) genes. Strong evidence was found to support the formation of multimeric complex involving A, B, C and SEP proteins, as mechanism which triggers flower development (see Robles and Pelaz, 2005 for references). In tomato, TM5 (Pnueli et al, 1994b) and TM29 (Ampomah-Dwamena et al, 2002) have been described as two SEP-like genes on the basis of their expression pattern and down-regulated phenotypes.…”

“…Most of the ABC genes belong to the MADS-box family encoding transcription factors, which are highly conserved among plant species. MADS proteins bind to DNA as multimeric complexes which ultimately control the development of floral organs (see Robles and Pelaz, 2005).…”

Regulation of Floral Induction in Citrus

“…In Arabidopsis, several MADS-box genes, such as APETALA (AP) 1, 2, and 3, PISTILLATA, and AGAMOUS, are reported to establish floral organ identity (Robles and Pelaz, 2005). These floral organ identity genes are regulated by flower meristem identity genes such as AP1 and LEAFY (LFY) (Jack, 2004).…”

Identification and expression analysis of the Cyclamen persicum MADS-box gene family

“…as floral organ identity genes, which are involved in the specification of all floral organs in cooperation with other gene classes (Ditta et al 2004;Honma and Goto 2001;Pelaz et al 2000;Robles and Pelaz 2005;Theissen 2001). With the exception of APETALA2 which belongs to the AP2/EREBP family, almost all transcription factors included in the ABCDE model belong to the MADS-box family (Riechmann et al 1997;SchwarzSommer et al 1990).…”