Plant Cell 27, 1046–1060 (2015).

Credit: ROBERTO NISTRI / ALAMY

Although our understanding of the gene networks that control inflorescence development in Arabidopsis has been significantly advanced, little is known about the development of more complex inflorescence architecture. Using the pea plant (Pisum sativum) as a model, Frances C. Sussmilch, at the University of Tasmania, and colleagues now find that a homologue of the bZIP transcription factor FD, VEGETATIVE2 (VEG2), plays a vital role in compound inflorescence development.

Unlike the inflorescence of Arabidopsis, a simple ‘raceme’, peas have secondary inflorescences bearing flowers on lateral branches, known as compound racemes. The researchers focused on two pea mutants, veg2-1 and veg2-2, that exhibit nonflowering and delayed-flowering phenotypes, respectively. The late-flowering veg2-2 mutant showed abnormal inflorescence and floral morphology. Through genetic mapping and sequence analysis, they confirmed the VEG2 gene to be a homologue of FD. Examination of the mutant phenotypes and gene expression showed that VEG2 is expressed in the apex and functions throughout the developmental stages of the compound raceme — that is from flower initiation to secondary inflorescence development.

VEG2 regulates flowering and meristem identity genes as these genes were misexpressed in the veg2 mutants. The researchers showed that the regulatory effect of VEG2 on the downstream genes might be mediated through its interaction with the five FT proteins in pea. This significant mechanistic understanding of compound inflorescence development may facilitate the future breeding of legume crop species with modified inflorescence architecture.