Biology subjects

Mullineaux, P. M.

Publications and source records attributed to Mullineaux, P. M..

3 recordsLinked to original sources

bioRxiv2024

ROS responsive Aux/IAA multimerization modulates auxin responses

Reactive oxygen species (ROS) function as key signals in plants to enable adaptation to environmental stresses. Plant roots respond to transient water stress by temporarily ceasing branching using the acclimative response xerobranching1. In this study, we report that a rapid ROS burst regulates Xerobranching by inducing multimerization of auxin repressor protein IAA3/SHY2. Mutations in specific cysteine residues in IAA3/SHY2 disrupt redox-mediated multimerization and interaction with co-repressor TPL, but not with auxin response partner ARF7 and auxin receptor TIR1. ROS-mediated oligomerization of IAA3/SHY2 is required for efficient ARF mediated target gene repression during Xerobranching and lateral root emergence. We demonstrate that AUX/IAA proteins vary in their redox mediated multimerization, revealing a new auxin response regulatory mechanism that directly connects ROS sensing to auxin signalling. Our study reveals how ROS, auxin and water stress intersect to shape acclimative responses in plant roots and maintain their phenotypic plasticity.

plant biology↗

bioRxiv2024

A novel glutathione peroxidase-based biosensor disentangles differential subcellular accumulation of H2O2 and lipid hydroperoxides

Hydrogen peroxide (H2O2) and lipid hydroperoxides (LOOH) are initiators and transducers of inter- and intra-cellular signaling in response to diverse environmental, pathological and developmental cues. The accumulation of both H2O2 and LOOH is often temporally and spatially coincident in tissues, but it is unknown if this coincidence extends to subcellular compartments. If distinct accumulation of different peroxides occurs at this smaller spatial scale, then it would be an important factor in signaling specificity. Fusion of the redox-sensitive (ro)GFP2 to the Saccharomyces cerevisiae (yeast) OXIDANT RECEPTOR PEROXIDASE1 (ORP1), also known as GLUTATHIONE PEROXIDASE3 (GPX3), created a now widely used biosensor that is assumed to detect H2O2 in vivo. This is despite monomeric GPX enzymes, such as ORP1/GPX3, possessing wide peroxide substrate specificities. Consequently, we confirmed in vitro that roGFP2-ORP1 is not only oxidized by H2O2, but also by phospholipid fatty acid peroxides generated in lecithin-derived liposomes by lipoxygenase-catalyzed peroxidation. This led us to doubt that roGFP2-ORP1 in vivo is specific for H2O2. To address this issue of peroxide specificity, we constructed a modified biosensor called roGFP2-synORP1. This version has greatly diminished reactivity towards phospholipid fatty acid peroxides but retains high sensitivity for H2O2. These two roGFP2-based biosensors, targeted to chloroplasts, cytosol and the nucleus, were quantitatively imaged in parallel in Nicotiana benthamiana abaxial epidermal cells experiencing high light- and herbicide-induced photo-oxidative stress. From differential patterns of oxidation of these probes, we inferred that the chloroplasts accumulated both peroxide types. In contrast, LOOH and H2O2 accumulated exclusively in the cytosol and nucleus respectively. Therefore, this suggests that the signalling networks initiated by different peroxides will have a distinct spatial component.

molecular biology↗

bioRxiv2020

Time series transcriptomics reveals a BBX32-directed control of dynamic acclimation to high light in mature Arabidopsis leaves

The photosynthetic capacity of mature leaves increases after several days exposure to constant or intermittent episodes of high light (HL) and is manifested primarily as changes in chloroplast physiology. This is termed dynamic acclimation but how it is initiated and controlled is unknown. From fully expanded Arabidopsis leaves, we determined HL-dependent changes in transcript abundance of 3844 genes in a 0-6h time-series transcriptomics experiment. It was hypothesised that among such genes were those that contribute to the initiation of dynamic acclimation. By focussing on HL differentially expressed transcription (co-)factor (TF) genes and applying dynamic statistical modelling to the temporal transcriptomics data, a gene regulatory network (GRN) of 47 predominantly photoreceptor-regulated (co)-TF genes was inferred. The most connected gene in this network was B-BOX DOMAIN CONTAINING PROTEIN32 (BBX32). Plants over-expressing BBX32 were strongly impaired in dynamic acclimation and displayed perturbed expression of genes involved in its initiation. These observations led to demonstrating that as well as regulation of dynamic acclimation by BBX32, CRYPTOCHROME1, LONG HYPOCOTYL5, CONSTITUTIVELY PHOTOMORPHOGENIC1 and SUPPRESSOR OF PHYA-105 are also important regulators of this process. Additionally, the BBX32-centric GRN provides a view of the transcriptional control of dynamic acclimation distinct from other photoreceptor-regulated processes, such as seedling photomorphogenesis.

plant biology↗