FORMOSA controls cell division and expansion during floral development in Antirrhinum majus

Abstract

Control of organ size is the product of coordinated cell division and expansion. In plants where one of these pathways is perturbed, organ size is often unaffected as compensation mechanisms are brought into play. The number of founder cells in organ primordia, dividing cells, and the period of cell proliferation determine cell number in lateral organs. We have identified the Antirrhinum FORMOSA (FO) gene as a specific regulator of floral size. Analysis of cell size and number in the fo mutant, which has increased flower size, indicates that FO is an organ-specific inhibitor of cell division and activator of cell expansion. Increased cell number in fo floral organs correlated with upregulation of genes involved in the cell cycle. In Arabidopsis the AINTEGUMENTA (ANT) gene promotes cell division. In the fo mutant increased cell number also correlates with upregulation of an Antirrhinum ANT-like gene (Am-ANT) in inflorescences that is very closely related to ANT and shares a similar expression pattern, suggesting that they may be functional equivalents. Increased cell proliferation is thought to be compensated for by reduced cell expansion to maintain organ size. In Arabidopsis petal cell expansion is inhibited by the BIGPETAL (BPE) gene, and in the fo mutant reduced cell size corresponded to upregulation of an Antirrhinum BPE-like gene (Am-BPE). Our data suggest that FO inhibits cell proliferation by negatively regulating Am-ANT, and acts upstream of Am-BPE to coordinate floral organ size. This demonstrates that organ size is modulated by the organ-specific control of both general and local gene networks.

Virus induced gene silencing in Antirrhinum majus using the Cucumber mosaic virus vector: Functional analysis of the AINTEGUMENTA (Am-ANT) gene of A. majus

“…In recent studies, partial cDNA of a putative ANT-like ortholog with the AP2 domains in Antirrhinum majus was cloned using a yeast one-hybrid approach; the open reading frame (ORF) of ANT (Am-ANT) of A. majus was not been determined (Delgado-Benarroch et al, 2009). The reported sequence for Am-ANT is similar to the NtANTL and At-ANT genes.…”

“…The reported sequence for Am-ANT is similar to the NtANTL and At-ANT genes. In situ hybridization in A. majus to analyze the expression of Am-ANT revealed that Am-ANT was expressed in floral meristems and in early floral organ primordia (Delgado-Benarroch et al, 2009). As floral organs matured, the expression of Am-ANT decreased in sepals at an early stage and in stamens at a late stage.…”

“…To clone the AINTEGUMENTA-like gene (Am-ANT) in Antirrhinum majus, we first conducted rapid amplification of the cDNA ends (3'RACE and 5'RACE) to complete the ORF beyond the partial cDNA sequence for Am-ANT reported by Delgado-Benarroch et al (2009). The fulllength cDNA of Am-ANT is 2,148 bp long, of which 1,581 bp encode a protein of 526 amino acids; the coding sequence is 29 % and 52 % identical at the nucleotide level to the At-ANT and the NtANTL, respectively (Fig.…”

“…The ANT protein has two copies of the AP2 domains, R1 and R2. Recently, a partial cDNA sequence of the At-ANT homolog in Antirrhinum majus (Am-ANT) was reported (Delgado-Benarroch et al, 2009). Here, we used virus-induced gene silencing (VIGS) to analyze the function of the reported Am-ANT.…”

The mutants compacta ähnlich, Nitida and Grandiflora define developmental compartments and a compensation mechanism in floral development in Antirrhinum majus

“…Recently, a compensation mechanism that shows a decrease in cell size and increased cell division has been described for integument development in Arabidopsis (Truernit and Haseloff 2008), suggesting that tissues other than leaves might share this mechanism of growth control. Furthermore, we have found a similar phenotype in the formosa mutant of A. majus characterised by increased petal size and smaller cells (Delgado-Benarroch et al 2009). In the present work, we showed that the mutant coan affected petal, stamen and style development by cell division.…”