Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.39

SUMO REGULATES FLOWERING IN ARABIDOPSIS

G. MURTAS*, P. H. REEVES*^,**, Y.-F. FU*^,**, I. BANCROFT*, C. DEAN*, G. COUPLAND*^,**

*) John Innes Centre, Colney Lane Norwich NR4 7UH UK

**) Max Planck Institute for Plant Breeding, Carl von Linne Weg, 10, D-50829 Cologne, Germany

flowering, development, SUMO

Flowering is controlled by a network of genetic pathways in Arabidopsis thaliana. We have characterised an extreme early flowering mutant early in short days 4 (esd4) that dramatically accelerates the transition from vegetative growth to flowering in Arabidopsis. In addition to its flowering time phenotype, esd4 has effects on plant development, which include broadening of the silique, alterations in phylotaxy and a reduction in stature.

Genetic analysis indicates that ESD4 is most closely associated with the autonomous pathway. The MADS box transcription factor FLOWERING LOCUS C (FLC) plays a central role within this pathway as a potent repressor of flowering and the flowering phenotype of esd4 is partly caused by reduced abundance of FLC mRNA, as well as an FLC-independent mechanism.

By map-based cloning we have isolated ESD4 and this gene encodes a nuclear protein containing a segment of over 200 amino acids at the carboxy-terminus with strong similarity to yeast and animal proteases that are specific for the protein modifier Small Ubiquitin-related Modifier (SUMO). We demonstrate that ESD4 has a similar protease function by showing that in vitro it processes the precursor of Arabidopsis SUMO (AtSUMO). Moreover, in esd4 mutants the abundance of free AtSUMO is reduced, suggesting that in vivo the ESD4 recycles AtSUMO from conjugates.

The effects of mutations in SUMO metabolism have not been described in a multicellular organism and this is the first demonstration of the importance of SUMO in plant development. ESD4 defines important roles for protein modification by AtSUMO within the genetic network that regulates flowering and in other aspects of plant development.