Biology subjects

Holdsworth, M. J.

Publications and source records attributed to Holdsworth, M. J..

4 recordsLinked to original sources

bioRxiv2026

Functional diversification of UBP6 in plant immunity through N-degron pathway regulation

Deubiquitylases are key proteolytic regulators of ubiquitin-dependent cellular processes, catalyzing the removal or remodelling of ubiquitin modifications on substrate proteins, including those targeted for proteasomal degradation. UBIQUITIN PROTEASE (UBP)6 is a deubiquitylase that promotes the abundance of NONEXPRESSOR OF PATHOGENESIS RELATED GENES (NPR)1, a conserved master regulator of plant immunity. Here, we show that the Arabidopsis thaliana protease METACASPASE (MC)9 site-specifically processes UBP6, generating the E157-UBP6 proteoform, whose stability is controlled by the Arginyl-transferase (ATE) N-degron pathway. We observed that pathogen recognition both triggers UBP6 cleavage and leads to conditional stabilisation of E157 UBP6, which is enhanced as the defence response intensifies. Our data suggest that E157 UBP6, which lacks deubiquitylating activity, may induce inhibition of the proteasome, elevating NPR1 levels and enhancing salicylic acid (SA) induced gene activation, all of which collectively contribute to restricting pathogen growth. Thus, UBP6 cleavage and N-degron pathway regulation provide distinct proteoforms of UBP6 with specific effects on the immune processes.

plant biology↗

bioRxiv2026

Conditional stability of HY5 through the ATE N-degron pathway regulates environmental responses in Arabidopsis thaliana

The N-degron pathways of ubiquitin mediated proteolysis target proteins for degradation dependent on their amino terminal residue, often produced after protease activity. Very few substrates have been identified in plants even though enzymes of these pathways are highly conserved in eukaryotes. Here we identify ELONGATED HYPOCOTYL5 (HY5), an important transcriptional regulator involved in many aspects of plant development, as a target for the endopeptidase METACASPASE (MC)9, producing the carboxy-terminal protein fragment (proteoform) E59-HY5. E59-HY5 is shown to be a substrate of the arginyl transferase (ATE) N-degron pathway, and influences physiological processes known to be controlled by HY5, including photomorphogenesis and the unfolded protein response. Conditional stability of E59-HY5 was shown to result from environmentally controlled ATE function, which may highlight a general mechanism for N-degron pathway regulation of proteoform and proteome function during growth and development.

plant biology↗

bioRxiv2024

The role of ERFVIIs as oxygen-sensing transducers in the evolution of land plant response to hypoxia

The transcriptional response to low oxygen (hypoxia) in the flowering plant Arabidopsis thaliana is transduced through group VII Ethylene Response Factor (ERFVII) transcription factors, whose proteolysis is oxygen-dependent via the PLANT CYSTEINE OXIDASE (PCO) N-degron pathway. When and how this response to hypoxia evolved in land plants remains unknown. Here we investigated the conservation and divergence of transcriptional responses to hypoxia in major land plant clades. We identified induction of gene functions associated with glycolysis and fermentation as part of a conserved response across all land plant divisions. Our results indicate that ERFVIIs appeared in the last common ancestor of vascular plants with true roots, concurrently with oxygen-dependent destabilisation, to regulate hypoxia-adaptive genes. Proteins from other ERF groups have been recruited multiple times in different clades as substrates of the PCO N-degron pathway. Our results demonstrate that the response of land plants to hypoxia has been refined in derived clades through the evolution of ERFVIIs as transcriptional transducers, that occurred concomitantly with the appearance of vascular systems and roots as foraging systems through hypoxic soil.

plant biology↗

bioRxiv2019

Ethylene-mediated nitric oxide depletion pre-adapts plants to hypoxia stress

Timely perception of adverse environmental changes is critical for survival. Dynamic changes in gases are important cues for plants to sense environmental perturbations, such as submergence. In Arabidopsis thaliana, changes in oxygen and nitric oxide (NO) control the stability of ERFVII transcription factors. ERFVII proteolysis is regulated by the N-degron pathway and mediates adaptation to flooding-induced hypoxia. However, how plants detect and transduce early submergence signals remains elusive. Here we show that plants can rapidly detect submergence through passive ethylene entrapment and use this signal to pre-adapt to impending hypoxia. Ethylene can enhance ERFVII stability prior to hypoxia by increasing the NO-scavenger PHYTOGLOBIN1. This ethylene-mediated NO depletion and consequent ERFVII accumulation pre-adapts plants to survive subsequent hypoxia. Our results reveal the biological link between three gaseous signals for the regulation of flooding survival and identifies novel regulatory targets for early stress perception that could be pivotal for developing flood-tolerant crops.

plant biology↗