EMF Genes Maintain Vegetative Development by Repressing the Flower Program in Arabidopsis

Abstract

The EMBRYONIC FLOWER ( EMF ) genes EMF1 and EMF2 are required to maintain vegetative development and repress flower development. EMF1 encodes a putative transcriptional regulator, and EMF2 encodes a Polycomb group protein homolog. We examined expression profiles of emf mutants using GeneChip technology. The high degree of overlap in expression changes from the wild type among the emf1 and emf2 mutants was consistent with the functional similarity between the two genes. Expression profiles of emf seedlings before flower development were similar to that of Arabidopsis flowers, indicating the commitment of germinating emf seedlings to the reproductive fate. The germinating emf seedlings ectopically expressed flower organ genes, suggesting that vegetative development in wild-type plants results from EMF repression of the flower program, directly or indirectly. In addition, the seed development program is derepressed in the emf1 mutants. Gene expression analysis showed no clear regulation of CONSTANS ( CO ), FLOWERING LOCUS T ( FT ), LEAFY ( LFY ), and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 by EMF1 . Consistent with epistasis results that co , lfy , or ft cannot rescue rosette development in emf mutants, these data show that the mechanism of EMF -mediated repression of flower organ genes is independent of these flowering genes. Based on these findings, a new mechanism of EMF-mediated floral repression is proposed.

EMBRYONIC FLOWER1 and ULTRAPETALA1 Act Antagonistically on Arabidopsis Development and Stress Response

“…S1A), whereas emf1-2 ult1-3 plants look liked the emf1-2 plants, producing oval-shaped, petioleless cotyledons that later become carpelloid, extremely short hypocotyls, and no leaf primordia (Supplemental Fig. S1A; Chen et al, 1997;Moon et al, 2003). Since the emf1-2 ult1-3 double mutants are similar to emf1-2 single mutants, we concluded that the ult1-3 mutation cannot rescue the emf1-2 phenotypes.…”

Deciphering the Role of POLYCOMB REPRESSIVE COMPLEX1 Variants in Regulating the Acquisition of Flowering Competence in Arabidopsis

“…According to previous results in Arabidopsis, the PRC1 RING finger proteins AtBMI1 and AtRING1 are required for the repression of the seed maturation program after germination, whereas EMF1 is required for the repression of the floral program during vegetative development (Moon et al, 2003;Calonje et al, 2008;Bratzel et al, 2010;Chen et al, 2010), indicating that different PRC1 components are crucial for the regulation of different subsets of targets. On the other hand, other results suggest that all these components are required for the regulation of a different subset of target genes.…”

PoplarFT2Shortens the Juvenile Phase and Promotes Seasonal Flowering

“…It is becoming clear in Arabidopsis that modification of chromatin structure, by disruption of Polycomb group protein complexes at target loci, plays a major role in the floral transition. For example, the Polycomb group proteins EMBRYONIC FLOWER2 and FERTIL-IZATION-INDEPENDENT ENDOSPERM act as repressors of the floral homoeotic genes during embryo and vegetative development (Kinoshita et al, 2001;Yoshida et al, 2001;Moon et al, 2003). Specifically, the plant homeodomain finger protein, EARLY BOLTING IN SHORT DAYS, represses FT expression (Pineiro et al, 2003).…”