Genetic and Phenotypic Analysis of Shoot Apical and Floral Meristem Development.

The shoot apical and floral meristems (SAM and FM, respectively) of Arabidopsis thaliana contain reservoirs of self-renewing stem cells that function as sources of progenitor cells for organ formation during development. The primary SAM produces all the aerial structures of the adult plant, while the FMs generate the four types of floral organs. Consequently, aberrant SAM and FM activity can profoundly affect vegetative and reproductive plant morphology.

Interactive CLV3, CLE16 and CLE17 signaling mediates stem cell homeostasis in the Arabidopsis shoot apical meristem.

The ability of plants to grow and form organs throughout their lifetime is dependent on their sustained stem cell activity. These stem cell populations are maintained by intricate networks of intercellular signaling pathways. In Arabidopsis thaliana, the small secreted peptide CLAVATA3 (CLV3) controls shoot apical meristem (SAM) maintenance by activating a signal transduction pathway that modulates the expression of the homeodomain transcription factor WUSCHEL (WUS).

A reevaluation of the role of the trihelix transcription factors as repressors of the seed maturation program.

Developmental transitions are typically tightly controlled at the transcriptional level. Two of these transitions involve the induction of the embryo maturation program midway through seed development and its repression during the vegetative phase of plant growth. Very little is known about the factors responsible for this regulation during early embryogenesis, and only a couple of transcription factors have been characterized as repressors during the postgerminative phase.

Peptide signaling molecules CLE5 and CLE6 affect Arabidopsis leaf shape downstream of leaf patterning transcription factors and auxin.

Intercellular signaling mediated by small peptides is critical to coordinate organ formation in animals, but whether extracellular polypeptides play similar roles in plants is unknown. Here we describe a role in Arabidopsis leaf development for two members of the CLAVATA3/ESR-RELATED peptide family, CLE5 and CLE6, which lie adjacent to each other on chromosome 2. Uniquely among the genes, and are expressed specifically at the base of developing leaves and floral organs, adjacent to the boundary with the shoot apical meristem.

The signaling peptide-encoding genes CLE16, CLE17 and CLE27 are dispensable for Arabidopsis shoot apical meristem activity.

The shoot apical meristem produces all of the leaves, stems and flowers of a flowering plant from a reservoir of stem cells at its growing tip. In Arabidopsis, the small polypeptide signaling molecule CLAVATA3 (CLV3), a member of the CLV3/EMBRYO SURROUNDING REGION-RELATED (CLE) gene family, is a key component of a negative feedback loop that maintains stem cell activity in shoot and floral meristems throughout development. Because in some plant species multiple CLE genes are involved in regulating shoot apical meristem activity, we tested the hypothesis that CLE genes other than CLV3 might function in stem cell homeostasis in Arabidopsis.