Biology subjects

Oldroyd, G. E. D.

Publications and source records attributed to Oldroyd, G. E. D..

3 recordsLinked to original sources

bioRxiv2026

4D spatial transcriptomics reveals nodule identity emerges through stacked parallel developmental programs

Legume root nodules enable symbiotic nitrogen fixation through the development of specialized cells that accommodate nitrogen-fixing bacteria intracellularly and support bacterial nitrogenase activity. Here, we present a 4D (3D space and time) spatial transcriptomic atlas of Medicago truncatula nodules and lateral roots, revealing specialized symbiotic cell types that develop alongside a conserved lateral-root-derived program that underpins vascularization. Spatial profiling of both plant and bacterial transcripts resolves distinct transcriptional states and previously unrecognized cell states. Spatial analysis of developmental regulator mutants uncovers a cascading series of cell-type-specific programs during nodule maturation. LSH1/LSH2 are central regulators of these programs, and lsh1/lsh2 mutants exhibit collapse of hormonal gradients and nodule identity. Strikingly, loss of nodule identity collapses to a primary-root identity rather than lateral-root fate. This work reveals how tissue complexity emerges through stacked developmental programs sustained in distinct cellular compartments, allowing the emergence of cell types specialized for harboring nitrogen-fixing bacteria. HIGHLIGHTSO_LI>136,000 cells define a 4D spatial atlas of nodules and lateral roots C_LIO_LI3D spatial and dual-species analysis resolves dynamic host and rhizobial cell states C_LIO_LIA shared meristem generates 3 spatially coordinated symbiotic, non-symbiotic, and vascular cell programs C_LIO_LILSH1/LSH2 are critical for regulatory programs underlying nodule development and identity C_LIO_LINodule identity loss collapses toward a primary root-associated state, not a lateral root fate C_LI

plant biology↗

bioRxiv2026

The demonstration of a single origin for nodule evolution, with nodule engineering in a non-nodulating species

The nitrogen-fixing root-nodule symbiosis provides a sustainable source of nitrogen for plants within the Nitrogen (N)-fixing clade (NFC). A debate has raged over whether nodulation evolved once, with many losses or multiple times following a predisposition event. Here we demonstrate that nodule-organogenesis is fully conserved between an actinorhizal nodulator Datisca glomerata and the legume Medicago truncatula, showing entirely conserved programmes for Nodule INception (NIN)-controlled development leading to nodule emergence. Convergent losses of N-fixation within the NFC is associated with loss of NIN and we show the engineering of nodule-like development into strawberry, a non-nodulating member of the NFC, through the repair of NIN-functionality. Similar NIN-engineering resulted in altered-root developmental responses in barley. Our work is consistent with the single-gain hypothesis, where repair of NIN can recapitulate nodules in species within the NFC, demonstrating that understanding the ancestral state of nodulation facilitates its engineering.

plant biology↗

bioRxiv2023

Cellular gibberellin dynamics govern indeterminate nodule development, morphologyand function

During nutrient scarcity, plants can adapt their developmental strategy to maximize their chance of survival. Such plasticity in development is underpinned by hormonal regulation, which mediates the relationship between environmental cues and developmental outputs. In legumes, endosymbiosis with nitrogen fixing bacteria (rhizobia) is a key adaptation for supplying the plant with nitrogen in the form of ammonium. Rhizobia are housed in lateral root-derived organs termed nodules that maintain an environment conducive to Nitrogenase in these bacteria. Several phytohormones are important for regulating the formation of nodules, with both positive and negative roles proposed for gibberellin (GA). In this study, we determined the cellular location and function of bioactive GA during nodule organogenesis using a genetically-encoded second generation GA biosensor, GPS2. We found endogenous bioactive GA accumulates locally at the site of nodule primordia, increasing dramatically in the cortical cell layers, persisting through cell divisions and maintaining accumulation in the mature nodule meristem. We show, through mis-expression of GA catabolic enzymes that suppress GA accumulation, that GA acts as a positive regulator of nodule growth and development. Furthermore, increasing or decreasing GA through perturbation of biosynthesis gene expression can increase or decrease the size of nodules, respectively. This is unique from lateral root formation, a developmental program that shares common organogenesis regulators. We link GA to a wider gene regulatory program by showing that cytokinin as well as nodule-identity genes induce and sustain GA accumulation necessary for nodule function.

plant biology↗