Shaping up the fruit: control of fruit size by an Arabidopsis B-sister MADS-box gene

Abstract

The final size and shape of fruits is determined by organogenesis. Organogenesis is the coordination of cell growth, cell differentiation and pattern formation. Individual genes have been identified that affect lateral organ growth. A majority of these characterized growth genes in Arabidopsis affect all lateral plant organs and few of these have been placed into a regulatory network controlling organ growth. We have recently characterized GORDITA (GOA), a MADS-box transcription factor, which represses cell expansion specifically in fruits and affects overall fruit size.1 Here we provide insights into a possible regulatory network in which GOA can function to regulate fruit growth. We further suggest how duplicated B-sister genes; GOA and TRANSPARENT TESTA 16 (TT16) could have acquired distinct regulatory roles.

Figure 1

The size of an organ is determined by cell proliferation and cell expansion. Many proteins have been identified in Arabidopsis that play a role in these processes, however, little is known about the regulatory networks that control these processes.

Figure 2

Patterning and growth during Arabidopsis fruit development. SHP1, SHP2, IND and ALC are necessary for patterning cells within the valve margin (vm). FUL represses the expression of these vm genes in the valves and RPL represses these vm genes in the replum. This sets up boundaries for patterning the various tissues of the fruit. JAG and other genes are necessary for proper FUL and vm gene expression. GOA represses fruit growth in the valves and FUL could repress GOA expression in the valves. Figure adapted from Dinneny et al. 2005.

Figure 3

Schematic diagram displaying distribution patterns of putative cis-regulatory elements in the promoter region of TT16 (predicted promoter 3.9 kb) and GOA (1.7 kb). These analyses were carried out using PLACE (www.dna.affrc.go.jp/PLACE; Plant Cis-acting Regulatory DNA Elements). Asterisks at vertical bars represents predicted putative cis-regulatory element present only in pGOA but not in pTT16.