Biology subjects

Hicks, G. R.

Publications and source records attributed to Hicks, G. R..

3 recordsLinked to original sources

bioRxiv2026

A family of metabolite damage-control phosphatases modulates ROS-induced autophagy and plant stress resilience

Autophagy is an intracellular recycling pathway with profound impacts on development, growth, and stress tolerance in eukaryotes. Therefore, unravelling signalling mechanisms that modulate the process has broad applicability. Here, we characterised a small organic molecule as an enhancer of autophagy across diverse plant lineages. Through an in vivo photoaffinity proteomics approach in Arabidopsis thaliana seedlings, we identified Domain of Unknown Function 89 (DUF89) proteins as molecular targets. Hereafter, we refer to these proteins as Reactive Metabolite Damage-Control Phosphatases (RMDPs), which are metabolite-repair phosphatases that clear reactive products. The new autophagy modulator is called RMDP inhbitor-1 (RMDPi-1) due to its demonstrated inhibitory effect on AtRMDP1 activity in vitro. Binding was further confirmed through co-incubation that thermostabilised the protein. Crystal structures of AtRMDP1 were obtained via X-ray diffraction, confirming binding of RMDPi-1 in the catalytic site and revealing a flexible region near the binding pocket that was absent in previous models. Molecular docking predicted two possible binding modes consistent with the observed electron density. RMDPi-1 treatment and the phosphatase gene knockout increased autophagic flux in Arabidopsis and Chlamydomonas reinhardtii, establishing a conserved effect. The observed autophagy response is linked to a spike in reactive oxygen species (ROS). AtRMDP knockout also results in higher ROS tolerance and greater biomass in Arabidopsis seedlings. Targeted and untargeted metabolomic experiments revealed that both pharmacological and genetic suppression of RMDP leads to accumulation of glycating agents and phosphate sugars, associating loss of RMDP activity to the ROS stress that induces alternate ROS-scavenging mechanisms, and autophagy. Taken together, our integrated chemical genetics approach reveals enhanced autophagy via inhibition of RMDP family members, which impacts on plant stress tolerance via conserved metabolite damage-control functions.

plant biology↗

bioRxiv2020

Endosidin20 targets cellulose synthase catalytic domain to inhibit cellulose biosynthesis

Cellulose is synthesized by rosette structured cellulose synthase (CESA) complexes (CSCs), each of which is composed of multiple units of CESAs in three different isoforms. CSCs rely on vesicle trafficking for delivery to the plasma membrane where they catalyze cellulose synthesis. Although the rosette structured CSCs were observed decades ago, it remains unclear what amino acids in plant CESA that directly participate in cellulose catalytic synthesis. It is also not clear how the catalytic activity of CSCs influences their efficient transport at the subcellular level. Here we report characterization of the small molecule Endosidin20 (ES20) and present evidence that it represents a new CESA inhibitor. We show data from chemical genetic analyses, biochemical assays, structural modeling, and molecular docking to support our conclusion that ES20 targets the catalytic site of Arabidopsis CESA6. Further, chemical genetic analysis reveals important amino acids that potentially form the catalytic site of plant CESA6. Using high spatiotemporal resolution live-cell imaging, we found that inhibition of CSC catalytic activity by inhibitor treatment, or by creating missense mutation at amino acids in the predicted catalytic site, causes reduced efficiency in CSC transport to the plasma membrane. Our results show that the catalytic activity of plant CSCs is integrated with subcellular trafficking dynamics. One sentence summaryEndosidin20 targets cellulose synthase at the catalytic site to inhibit cellulose synthesis and the inhibition of catalytic activity reduces cellulose synthase complex delivery to the plasma membrane.

plant biology↗

bioRxiv2019

Chemical screening pipeline for identification of specific plant autophagy modulators

Autophagy is a major catabolic process in eukaryotes with a key role in homeostasis, programmed cell death and aging. In plants, autophagy is also known to regulate agriculturally important traits such as stress resistance, longevity, vegetative biomass and seed yield. Despite its significance, there is still a shortage of reliable tools modulating plant autophagy. Here we describe the first robust pipeline for identification of specific plant autophagy-modulating compounds. Our screening protocol comprises four phases: (i) high-throughput screening of chemical compounds in cell cultures of Nicotiana tabacum; (ii) confirmation of the identified hits in planta using Arabidopsis thaliana; (iii) further characterization of the effect using conventional molecular biology methods; (iv) verification of chemical specificity on autophagy in planta. The methods detailed here streamline identification of specific plant autophagy modulators and aid in unravelling the molecular mechanisms of plant autophagy.

plant biology↗