Research

What do we study, and why?

In order to enhance their chances of survival and reproductive success, plants need to fine tune their growth and development in response to a wide range of diverse internal signals (e.g. hormones), environmental cues (e.g. temperature), and stresses (e.g. floods or pathogens).

We are interested in understanding the cellular mechanisms that plants have evolved to perceive these signals and transduce them into appropriate developmental and physiological outputs, with a particular focus on targeted protein degradation. We use a diverse range of molecular, genetic, biochemical and physiological approaches to achieve this, primarily in the model plant Arabidopsis.

Targeted protein degradation

Regulation of protein turnover is essential for controlling cellular responses and developmental outputs. In eukaryotes, the ubiquitin proteasome system (UPS) is the predominant pathway for targeted protein degradation; in this system, conjugation of ubiquitin molecules to protein substrates marks them for destruction by the 26S proteasome. The UPS is known to play a key role in almost all aspects of plant growth, development and stress response – for example, the perception of the majority of phytohormones is dependent on the UPS.

We investigate how plants use protein degradation as a signalling mechanism, and are especially interested in a specific branch of the UPS called the N-degron pathway (formerly N-end rule pathway). We are also interested in how protein degradation interats with protein translation to provide co-translational quality control.

The N-degron pathway

The N-degron pathway is an ancient and highly evolutionarily conserved proteolytic system that targets proteins for destruction based on the nature of their N-terminus (the beginning of the protein) (e.g., see Gibbs et al., 2014 Trends in Cell Biology). In plants, the pathway has emerged as an important regulator of oxygen and nitric oxide sensing and signalling, through its control of the stability of ERFVII transcription factors (e.g., Gibbs et al. and Licausi et al 2011 Nature; Gibbs et al., 2014 Molecular Cell).

We recently identified and characterised a new oxygen- and nitric oxide regulated target of the N-degron pathway - the polycomb repressive complex 2 (PRC2) subunit VERNALIZATION2 (VRN2) (Gibbs et al., 2018 Nature Communications), and we showed that this regulation is important for modulating shoot and root growth and development (Labandera et al., 2021 New Phytologist) As part of the PRC2, VRN2 regulates the epigenetic repression of gene targets through methylation of chromatin. This suggests that the N-degron pathway is important for sensing and transducing oxygen and nitric oxide signals into direct transcriptional and long-term epigenetic changes through targeting functionally distinct proteins to the same degradation pathway (ERFVIIs, VRN2). In work fuded by the ERC and the BBSRC, we are now exploring how control of VRN2 stability is linked to its functions during a wide range of processes. For example, we have recently shown that VRN2-PRC2 activity is required for the conditional repression of genes that promote growth, identifying a potential link between natural hypoxia gradients and the epigenetic control of gene expression (Osborne et al. 2025 Developmental Cell). Collaborative work now being led by Sjon Hartman (University of Freiburg) is investigating functions for VRN2 in mediating the epigenetic memory of flooding stress, and we are also working with Jose Gutierrez (University of Warwick) to understand how demethylase antagonists of PRC2 contribute to hypoxia - and other - responses.

Plant proteostasis

In addition to the N-degron pathway of proteolysis we are also interested in other post-translational protein modifications and mechanisms of proteostasis, and how these contribute to plant function. This includes:

(1) Investigating roles for N-terminal protein acetylation in plants (e.g., Gibbs, Bailey and Etherington (2022) Trends in Cell Biology; Huber et al. (2022) Frontiers in Plant Science)

(2) Investigating stress-associated functions for DOA10 E3 ligases that reside in the endoplasmic reticulum (ER) (e.g., Etherington et al. (2023) Plant Physiology)

(3) Investigating how components of the ubiquitin-proteasome system coordinate meiotic recombination (in collaboration with Eugenio Sanchez-Moran, University of Birmingham)

(4) Investigating mechanisms of co-translational protein and mRNA quality control via ribosome-associated E3 ligases.

Rice flooding trials at IRRI, Philippines, 2013. The N-end rule pathway was recently shown to regulate the transcriptional response to low oxygen, which has important implications for the development of flood tolerance in crops.

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