The TOPLESS corepressor regulates developmental switches in the bryophyte Physcomitrium patens that were critical for plant terrestrialisation.

The plant-specific TOPLESS (TPL) family of transcriptional corepressors is integral to multiple angiosperm developmental processes. Despite this, we know little about TPL function in other plants. To address this gap, we investigated the roles TPL plays in the bryophyte Physcomitrium patens, which diverged from angiosperms approximately 0.

Plants utilise ancient conserved peptide upstream open reading frames in stress-responsive translational regulation.

The regulation of protein synthesis plays an important role in the growth and development of all organisms. Upstream open reading frames (uORFs) are commonly found in eukaryotic messenger RNA transcripts and typically attenuate the translation of associated downstream main ORFs (mORFs). Conserved peptide uORFs (CPuORFs) are a rare subset of uORFs, some of which have been shown to conditionally regulate translation by ribosome stalling.

Repressor for hire! The vital roles of TOPLESS-mediated transcriptional repression in plants.

Transcriptional corepressors play important roles in establishing the appropriate levels of gene expression during growth and development. The TOPLESS (TPL) family of corepressors are critical for all plant life. TPLs are involved in numerous developmental processes and in the response to extrinsic challenges.

The loss of SMG1 causes defects in quality control pathways in Physcomitrella patens.

Nonsense-mediated mRNA decay (NMD) is important for RNA quality control and gene regulation in eukaryotes. NMD targets aberrant transcripts for decay and also directly influences the abundance of non-aberrant transcripts. In animals, the SMG1 kinase plays an essential role in NMD by phosphorylating the core NMD factor UPF1.

Conservation of Nonsense-Mediated mRNA Decay Complex Components Throughout Eukaryotic Evolution.

Nonsense-mediated mRNA decay (NMD) is an essential eukaryotic process regulating transcript quality and abundance, and is involved in diverse processes including brain development and plant defenses. Although some of the NMD machinery is conserved between kingdoms, little is known about its evolution. Phosphorylation of the core NMD component UPF1 is critical for NMD and is regulated in mammals by the SURF complex (UPF1, SMG1 kinase, SMG8, SMG9 and eukaryotic release factors).

Stem Cell Regulation by Arabidopsis WOX Genes.

Gene amplification followed by functional diversification is a major force in evolution. A typical example of this is seen in the WUSCHEL-RELATED HOMEOBOX (WOX) gene family, named after the Arabidopsis stem cell regulator WUSCHEL. Here we analyze functional divergence in the WOX gene family.

Flower development in the asterid lineage.

A complete understanding of the genetic control of flower development requires a comparative approach, involving species from across the angiosperm lineage. Using the accessible model plant Arabidopsis thaliana many of the genetic pathways that control development of the reproductive growth phase have been delineated. Research in other species has added to this knowledge base, revealing that, despite the myriad of floral forms found in nature, the genetic blueprint of flower development is largely conserved.

TOPLESS co-repressor interactions and their evolutionary conservation in plants.

Large-scale protein-protein interaction studies recently demonstrated that the Arabidopsis TPL/TPR family of transcriptional co-repressors is involved in a broad range of developmental processes. TPL/TPRs predominantly interact with transcription factors that contain repression domain (RD) sequences. Interestingly, RDs reported in the literature are quite diverse in sequence, yet TPL/TPRs interact with proteins containing all of the known motifs.

The TOPLESS interactome: a framework for gene repression in Arabidopsis.

Transcription factors activate or repress target gene expression or switch between activation and repression. In animals and yeast, Groucho/Tup1 corepressor proteins are recruited by diverse transcription factors to induce context-specific transcriptional repression. Two groups of Groucho/Tup1-like corepressors have been described in plants.

Tracing the evolution of the floral homeotic B- and C-function genes through genome synteny.

The evolution of the floral homeotic genes has been characterized using phylogenetic and functional studies. It is possible to enhance these studies by comparing gene content and order between species to determine the evolutionary history of the regulatory genes. Here, we use a synteny-based approach to trace the evolution of the floral B- and C-function genes that are required for specification of the reproductive organs.

Floral organ identity: 20 years of ABCs.

One of the early successes of the application of molecular genetics to study plant development was the discovery of a series of genes that act together, in an apparently simple combinatorial model, to specify the identity of the different organs of a flower. Widely known as the ABC model, this framework for understanding has been investigated and modified over the course of the last two decades. The cast list of genes has been defined and, as other chapters in this volume will show, great progress has been made in understanding how they are regulated, how they act together, what they do and how they have contributed to the evolution of the flower in its varied forms.

FORMOSA controls cell division and expansion during floral development in Antirrhinum majus.

Control of organ size is the product of coordinated cell division and expansion. In plants where one of these pathways is perturbed, organ size is often unaffected as compensation mechanisms are brought into play. The number of founder cells in organ primordia, dividing cells, and the period of cell proliferation determine cell number in lateral organs.

Conserved intragenic elements were critical for the evolution of the floral C-function.

The floral C-function, which specifies stamen and carpel development, played a pivotal role in the evolution of flowers. An important aspect of this was the establishment of mechanisms regulating the temporal and spatial expression domain of the C-function genes. Transcription of the Arabidopsis C-function gene AGAMOUS (AG) is tightly controlled by factors that interact with cis-elements within its large second intron.

Evolution in action: following function in duplicated floral homeotic genes.

Gene duplication plays a fundamental role in evolution by providing the genetic material from which novel functions can arise. Newly duplicated genes can be maintained by subfunctionalization (the duplicated genes perform different aspects of the original gene's function) and/or neofunctionalization (one of the genes acquires a novel function). PLENA in Antirrhinum and AGAMOUS in Arabidopsis are the canonical C-function genes that are essential for the specification of reproductive organs.

Studying the interactome with the yeast two-hybrid system and mass spectrometry.

Protein interactions are crucial to the life of a cell. The analysis of such interactions is allowing biologists to determine the function of uncharacterized proteins and the genes that encode them. The yeast two-hybrid system has become one of the most popular and powerful tools to study protein-protein interactions.

CUPULIFORMIS establishes lateral organ boundaries in Antirrhinum.

Cupuliformis mutants are defective in shoot apical meristem formation, but cup plants overcome this early barrier to development to reach maturity. CUP encodes a NAC-domain transcription factor, homologous to the Petunia NAM and Arabidopsis CUC proteins. The phenotype of cup mutants differs from those of nam and cuc1 cuc2 in that dramatic organ fusion is observed throughout development.

An antirrhinum ternary complex factor specifically interacts with C-function and SEPALLATA-like MADS-box factors.

The development of floral reproductive organs requires the activity of plant MADS-box transcription factors (MBFs) belonging to the C function. The C function can only operate within a floral context, specified by MBFs belonging to the SEPALLATA class of proteins. Here we describe the specific interaction between a novel protein, MIP1, and C-function and SEPALLATA (SEP)-like MBFs.

Analysing protein-protein interactions with the yeast two-hybrid system.

Plant research is moving into the post-genomic era. Proteomic-based strategies are now being developed to study functional aspects of the genes predicted from the various genome-sequencing initiatives. All biological processes depend on interactions formed between proteins and the mapping of such interactions on a global scale is providing interesting functional insights.