BIG enhances Arg/N-degron pathway-mediated protein degradation to regulate Arabidopsis hypoxia responses and suberin deposition.

BIG/DARK OVEREXPRESSION OF CAB1/TRANSPORT INHIBITOR RESPONSE3 is a 0.5 MDa protein associated with multiple functions in Arabidopsis (Arabidopsis thaliana) signaling and development. However, the biochemical functions of BIG are unknown.

Analysis of higher plant N-degron pathway components and substrates via expression in S. cerevisiae.

Heterologous expression of enzymes can generate a background-free environment that facilitates investigation of enzyme properties, for instance to focus on particular isoforms in case of gene families, or on individual splicing variants. If a proper host can be found, in vivo assays are often simpler than overexpression and purification, followed by in vitro measurements, would be. We expressed plant ubiquitin ligase PRT6 in the budding yeast Saccharomyces cerevisiae for studies on activity and substrate preferences.

The paradox of the life sciences: How to address climate change in the lab: How to address climate change in the lab.

Addressing climate change and sustainability starts with individuals and moves up to institutional change. Here is what we as scientists in the life sciences can do to enact change.

Transcriptome, metabolome and suppressor analysis reveal an essential role for the ubiquitin-proteasome system in seedling chloroplast development.

Background: Many regulatory circuits in plants contain steps of targeted proteolysis, with the ubiquitin proteasome system (UPS) as the mediator of these proteolytic events. In order to decrease ubiquitin-dependent proteolysis, we inducibly expressed a ubiquitin variant with Arg at position 48 instead of Lys (ubK48R). This variant acts as an inhibitor of proteolysis via the UPS, and allowed us to uncover processes that are particularly sensitive to UPS perturbation.

A Yeast-Based Functional Assay to Study Plant N-Degron - N-Recognin Interactions.

The N-degron pathway is a branch of the ubiquitin-proteasome system where amino-terminal residues serve as degradation signals. In a synthetic biology approach, we expressed ubiquitin ligase PRT6 and ubiquitin conjugating enzyme 2 (AtUBC2) from in a strain with mutation in its endogenous N-degron pathway. The two enzymes re-constitute part of the plant N-degron pathway and were probed by monitoring the stability of co-expressed GFP-linked plant proteins starting with Arginine N-degrons.

Cellular Control of Protein Turnover via the Modification of the Amino Terminus.

The first amino acid of a protein has an important influence on its metabolic stability. A number of ubiquitin ligases contain binding domains for different amino-terminal residues of their substrates, also known as N-degrons, thereby mediating turnover. This review summarizes, in an exemplary way, both older and more recent findings that unveil how destabilizing amino termini are generated.

Conceptual and Methodological Considerations on mRNA and Proteins as Intercellular and Long-Distance Signals.

High-throughput studies identified approximately one-fifth of Arabidopsis protein-encoding transcripts to be graft transmissible and to move over long distances in the phloem. In roots, one-fifth of transcription factors were annotated as non-cell autonomous, moving between cells. Is this massive transport a way of interorgan and cell-cell communication or does it serve different purposes? On the tissue level, many microRNAs (miRNAs) and all small interfering RNAs (siRNAs) act non-cell autonomously.

Sumoylation and phosphorylation: hidden and overt links.

Post-translational modifications are essential mediators between stimuli from development or the environment and adaptive transcriptional patterns. Recent data allow a first glimpse at how two modifications, phosphorylation and sumoylation, act interdependently to modulate stress responses. In particular, many components of the SUMO conjugation system are phosphoproteins, and some regulators and enzymes of protein phosphorylation can be sumoylated.

tRNA-Related Sequences Trigger Systemic mRNA Transport in Plants.

In plants, protein-coding mRNAs can move via the phloem vasculature to distant tissues, where they may act as non-cell-autonomous signals. Emerging work has identified many phloem-mobile mRNAs, but little is known regarding RNA motifs triggering mobility, the extent of mRNA transport, and the potential of transported mRNAs to be translated into functional proteins after transport. To address these aspects, we produced reporter transcripts harboring tRNA-like structures (TLSs) that were found to be enriched in the phloem stream and in mRNAs moving over chimeric graft junctions.

ALTERED MERISTEM PROGRAM1 suppresses ectopic stem cell niche formation in the shoot apical meristem in a largely cytokinin-independent manner.

Plants are able to reiteratively form new organs in an environmentally adaptive manner during postembryonic development. Organ formation in plants is dependent on stem cell niches (SCNs), which are located in the so-called meristems. Meristems show a functional zonation along the apical-basal axis and the radial axis.

MPB2C, a microtubule-associated protein, regulates non-cell-autonomy of the homeodomain protein KNOTTED1.

Plasmodesmata establish a pathway for the intercellular trafficking of viral movement proteins and endogenous non-cell-autonomous proteins, such as the two closely related meristem-maintaining KNOTTED1-like homeobox (KNOX) proteins Zea mays KNOTTED1 (KN1) and Arabidopsis thaliana SHOOTMERISTEMLESS (STM). KNOX family members are DNA binding proteins that regulate the transcriptional activity of target genes in conjunction with BEL1-like homeodomain proteins. It has been shown previously, using in vivo transport assays, that the C-terminal domain of KN1, including the homeodomain, is necessary and sufficient for cell-to-cell transport through plasmodesmata.