miR394 enhances WUSCHEL-induced somatic embryogenesis in Arabidopsis thaliana.

Many plant species can give rise to embryos from somatic cells after a simple hormone treatment, illustrating the remarkable developmental plasticity of differentiated plant cells. However, many species are recalcitrant to somatic embryo formation for unknown reasons, which poses a significant challenge to agriculture, where somatic embryogenesis is an important tool to propagate desired genotypes. The micro-RNA394 (miR394) promotes shoot meristem maintenance in Arabidopsis thaliana, but the underlying mechanisms have remained elusive.

The role of AUX1 during lateral root development in the domestication of the model C4 grass Setaria italica.

C4 photosynthesis increases the efficiency of carbon fixation by spatially separating high concentrations of molecular oxygen from Rubisco. The specialized leaf anatomy required for this separation evolved independently many times. The morphology of C4 root systems is also distinctive and adapted to support high rates of photosynthesis; however, little is known about the molecular mechanisms that have driven the evolution of C4 root system architecture.

B1-type cyclins control microtubule organization during cell division in Arabidopsis.

Flowering plants contain a large number of cyclin families, each containing multiple members, most of which have not been characterized to date. Here, we analyzed the role of the B1 subclass of mitotic cyclins in cell cycle control during Arabidopsis development. While we reveal CYCB1;5 to be a pseudogene, the remaining four members were found to be expressed in dividing cells.

Regulatory function of homeodomain-leucine zipper (HD-ZIP) family proteins during embryogenesis.

Homeodomain-leucine zipper proteins (HD-ZIPs) form a plant-specific family of transcription factors functioning as homo- or heterodimers. Certain members of all four classes of this family are involved in embryogenesis, the focus of this review. They support auxin biosynthesis, transport and response, which are in turn essential for the apical-basal patterning of the embryo, radicle formation and outgrowth of the cotyledons.

The plant-specific CDKB1-CYCB1 complex mediates homologous recombination repair in Arabidopsis.

Upon DNA damage, cyclin-dependent kinases (CDKs) are typically inhibited to block cell division. In many organisms, however, it has been found that CDK activity is required for DNA repair, especially for homology-dependent repair (HR), resulting in the conundrum how mitotic arrest and repair can be reconciled. Here, we show that Arabidopsis thaliana solves this dilemma by a division of labor strategy.

ZLL/AGO10 maintains shoot meristem stem cells during Arabidopsis embryogenesis by down-regulating ARF2-mediated auxin response.

Background: The shoot meristem gives rise to new organs throughout a plant's life by the activity of pluripotent stem cells in the meristem center. Organ initiation at the periphery of the shoot meristem is triggered by the accumulation of the phytohormone auxin at the initiation site. Loss-of-function mutants of the ZWILLE/ARGONAUTE10/PINHEAD (ZLL/AGO10/PNH) gene terminate shoot meristem stem cells late in embryogenesis and can form a leaf or a leaf-like structure instead, indicating that AGO10 activity is required to maintain shoot meristem stem cells undifferentiated.

Accession-specific modifiers act with ZWILLE/ARGONAUTE10 to maintain shoot meristem stem cells during embryogenesis in Arabidopsis.

Background: Stem cells located in the centre of the shoot apical meristem are required for the repetitive formation of new organs such as leaves, branches and flowers. In Arabidopsis thaliana, the ZWILLE/PINHEAD/AGO10 (ZLL) gene encodes a member of the ARGONAUTE (AGO) protein family and is required to maintain shoot meristem stem cells during embryogenesis. In the Landsberg erecta (Ler) acession, ZLL is essential for stem cell maintenance, whereas in the Columbia (Col) accession its requirement appears masked by genetic modifiers.

BAC-recombineering for studying plant gene regulation: developmental control and cellular localization of SnRK1 kinase subunits.

Recombineering, permitting precise modification of genes within bacterial artificial chromosomes (BACs) through homologous recombination mediated by lambda phage-encoded Red proteins, is a widely used powerful tool in mouse, Caenorhabditis and Drosophila genetics. As Agrobacterium-mediated transfer of large DNA inserts from binary BACs and TACs into plants occurs at low frequency, recombineering is so far seldom exploited in the analysis of plant gene functions. We have constructed binary plant transformation vectors, which are suitable for gap-repair cloning of genes from BACs using recombineering methods previously developed for other organisms.

Cullin 4-ring finger-ligase plays a key role in the control of endoreplication cycles in Arabidopsis trichomes.

One of the predominant cell-cycle programs found in mature tissues is endoreplication, also known as endoreduplication, that leads to cellular polyploidy. A key question for the understanding of endoreplication cycles is how oscillating levels of cyclin-dependent kinase activity are generated that control repeated rounds of DNA replication. The APC/C performs a pivotal function in the mitotic cell cycle by promoting anaphase and paving the road for a new round of DNA replication.

Endoreplication controls cell fate maintenance.

Cell-fate specification is typically thought to precede and determine cell-cycle regulation during differentiation. Here we show that endoreplication, also known as endoreduplication, a specialized cell-cycle variant often associated with cell differentiation but also frequently occurring in malignant cells, plays a role in maintaining cell fate. For our study we have used Arabidopsis trichomes as a model system and have manipulated endoreplication levels via mutants of cell-cycle regulators and overexpression of cell-cycle inhibitors under a trichome-specific promoter.