Quantitative levels of Deficiens and Globosa during late petal development show a complex transcriptional network topology of B function.

The transcriptional network topology of B function in Antirrhinum, required for petal and stamen development, is thought to rely on initial activation of transcription of DEFICIENS (DEF) and GLOBOSA (GLO), followed by a positive autoregulatory loop maintaining gene expression levels. Here, we show that the mutant compacta (co), whose vegetative growth and petal size are affected, plays a role in B function. Late events in petal morphogenesis such as development of conical cell area and scent emissions were reduced in co and def (nicotianoides) (def (nic) ), and absent in co def (nic) double mutants, suggesting a role for CO in petal identity.

A molecular recombination map of Antirrhinum majus.

Background: Genetic recombination maps provide important frameworks for comparative genomics, identifying gene functions, assembling genome sequences and for breeding. The molecular recombination map currently available for the model eudicot Antirrhinum majus is the result of a cross with Antirrhinum molle, limiting its usefulness within A. majus.

Floral organ size control: interplay between organ identity, developmental compartments and compensation mechanisms.

Growth of lateral organs is a complex mechanism that starts with formation of lateral primordia. Basal developmental programs like polarity, organ identity and environmental cues influence the final organ size achieved via coordinated cell division and expansion. Recent evidence shows that the precise balance between these two processes, known as compensation mechanisms, seems to be influenced by the identity of the organ.

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

In order to improve our understanding of floral size control we characterised three mutants of Antirrhinum majus with different macroscopic floral phenotypes. The recessive mutant compacta ähnlich has smaller flowers affected mainly in petal lobe expansion, the dominant mutant Grandiflora has overall larger organs, whilst the semidominant mutation Nitida exhibits smaller flowers in a dose-dependent manner. We developed a cell map in order to establish the cellular phenotypes of the mutants.

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

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.

Genetic control of floral size and proportions.

Floral size is an ecologically important trait related to pollination success and genetic fitness. Independently of the sexual reproduction strategy, in many plants, floral size seems to be controlled by several genetic programs that are to some extent independent of vegetative growth. Flower size seems to be governed by at least two independent mechanisms, one controlling floral architecture that affects organ number and a second one controlling floral organ size.