The petunia MADS box gene FBP11 determines ovule identity.

Abstract

In contrast to the wealth of information relating to genes regulating floral meristem and floral organ identity, only limited data are available concerning genes that are involved in determining and regulating the identity and development of an ovule. We have recently isolated the floral binding protein 11 (FBP11) MADS box gene from petunia and found that it is expressed exclusively in ovule primordia and subsequently in the ovules, suggesting a role for this gene in ovule formation. To test this hypothesis, we constructed a recombinant gene in which the full-size FBP11 cDNA was placed under the control of a strong cauliflower mosaic virus 35S promoter. Transgenic petunia plants expressing this chimeric gene have ovulelike structures on the adaxial side of the sepals and the abaxial side of the petals. Detailed morphological studies showed that these ovulelike structures are true ovules. RNA gel blot analysis was performed to investigate ectopic FBP11 expression in relation to the expression of the closely related FBP7 gene and the putative petunia class C-type homeotic genes FBP6 and pMADS3. Our results indicate that FBP11 represents an ovule identity gene. A new model describing the mode of action of FBP11 as an additional class D MADS box gene is presented.

Gene and Genome Duplications in Plants

“…In A. thaliana, A function is involved in the specification of sepals and petals, B function in petal and stamen specification, C function in stamen and carpel specification, and E function participates in the specification of all floral organs (Coen and Meyerowitz, 1991;Colombo et al, 1995;Pelaz et al, 2000;Ditta et al, 2004). These functions are all encoded by members of separate MADS-box gene lineages, each of which shows evidence of multiple duplication events (Theissen, 2001).…”

Classification and phylogeny of the MADS-box multigene family suggest defined roles of MADS-box gene subfamilies in the morphological evolution of eukaryotes

“…These carpel-specific genes may well be functionally related to FBP7 and FBPll from petunia, for which mutant phenotypes obtained by cosuppression revealed a function in proper ovule development (Angenent et al 1995b). Recently, transgenic petunia plants ectopically expressing FBPll demonstrated that this gene determines ovule identity (Colombo et al 1995).…”

Altered expression of wheat AINTEGUMENTA homolog, WANT-1, in pistil and pistil-like transformed stamen of an alloplasmic line with Aegilops crassa cytoplasm

“…The initiation of ovule primordium formation is caused by expression of class D MADS-box genes such as Arabidopsis SEEDSTICK (STK) and petunia floral binding protein 7 (FBP7) and FBP11 (Angenent et al 1995;Colombo et al 1995;Favaro et al 2003). ARABIDOPSIS BSISTER (ABS) from Arabidopsis and FBP24 from petunia are members of the B sister subfamily, which are necessary to determine the identity of the endothelial layer within the inner integument of the ovule (Nesi et al 2002;de Folter et al 2006).…”