Stem cells self-renew and repeatedly produce differentiated cells during development and growth. The differentiated cells can be converted into stem cells in some metazoans and land plants with appropriate treatments. After leaves of the moss Physcomitrella patens are excised, leaf cells reenter the cell cycle and commence tip growth, which is characteristic of stem cells called chloronema apical cells. To understand the underlying molecular mechanisms, a digital gene expression profiling method using mRNA 5′-end tags (5′-DGE) was established. The 5′-DGE method produced reproducible data with a dynamic range of four orders that correlated well with qRT-PCR measurements. After the excision of leaves, the expression levels of 11% of the transcripts changed significantly within 6 h. Genes involved in stress responses and proteolysis were induced and those involved in metabolism, including photosynthesis, were reduced. The later processes of reprogramming involved photosynthesis recovery and higher macromolecule biosynthesis, including of RNA and proteins. Auxin and cytokinin signaling pathways, which are activated during stem cell formation via callus in flowering plants, are also activated during reprogramming in P. patens, although no exogenous phytohormone is applied in the moss system, suggesting that an intrinsic phytohormone regulatory system may be used in the moss.

The CYCLOIDEA (CYC) gene controls the development of zygomorphic flowers and the determination of adaxial identity of floral organs in the model developmental system of Antirrhinum majus. However, whether CYC homologue genes also control floral zygomorphy in monocotyledon Alstroemeria plants is yet unknown. In this study, we investigated CYC-like genes in the monocotyledons Alstroemeria aurea, A. magenta, and A. pelegrina var. rosea, all of which have zygomorphic flowers. Since the CYC gene belongs to the T-complex protein (TCP) gene family of transcription factors, cloning of CYC-like sequences was performed using rapid amplification of cDNA ends (RACE)-polymerase chain reaction (PCR) by using degenerate primers designed for the TCP domain. We cloned 1 CYC-like sequence each from A. aurea (AaTCP1, accession number AB714967 in the GenBank/EMBL/DDBJ databases) and A. magenta (AmTCP1, AB714970), and 2 CYC-like sequences from A. pelegrina var. rosea (ApTCP1, AB714968; and ApTCP2, AB714969). The deduced amino acid sequences of AaTCP1, AmTCP1, ApTCP1, and ApTCP2 shared 67.7%, 67.7%, 71.0%, and 64.5% identities, respectively, with the TCP domain in CYC. Molecular phylogenetic analysis indicated that 3 CYC-like genes from Alstroemeria belonged to the ZinTBL1b clade in the CYC-/tb1-like subfamily. Reverse transcription (RT)-PCR and in situ hybridization analyses showed that AaTCP1 transcripts were specifically detected in flower buds and localized in the base of adaxial inner perianth of A. aurea. These results suggest that CYC-like genes are also involved in the development of floral asymmetry and the determination of adaxial identity of floral organs in the monocotyledon Alstroemeria.