Biology subjects

Ditengou, F. A.

Publications and source records attributed to Ditengou, F. A..

7 recordsLinked to original sources

bioRxiv2023

Competence for transcellular infection in the root cortex involves a post-replicative, cell-cycle exit decision in Medicago truncatula

During root nodule symbiosis (RNS), cell-division activity is re-initiated and sustained in the root cortex to create a hospitable cellular niche. Such temporary and spatially confined site is required to render host cells compatible with the intracellular progression of rhizobia. Although it has been suggested that early infection events might involve a pre-mitotic cell-cycle arrest, this process has not been dissected with cellular resolution. Here, we show that a dual-colour Medicago histone reporter robustly identifies cells with different mitotic or endoreduplication activities in the root cortex. By imaging deep root tissues, we found that a confined trajectory of cortical cells that are transcellularly passed by infection threads are in a stage of the cell-cycle that is distinct from directly adjacent cells. Distinctive features of infected cells include nuclear widening and large-scale chromatin rearrangements consistent with a cell-cycle exit prior to differentiation. Using a combination of fluorescent reporters demarcating cell-cycle phase progression, we confirmed that a reduced proliferation potential and modulating the G2/M transition, a process possibly controlled by the NF-YA1 transcription factor, mark the success of rhizobial delivery to nodule cells.

plant biology↗

bioRxiv2020

Distinct signalling routes mediates intercellular and intracellular rhizobial infection in Lotus japonicus

Rhizobial infection of legume roots during development of nitrogen fixing root nodules occurs either intracellularly though plant derived infection threads traversing the epidermal and cortical cell layers to deliver the bacteria or intercellularly via bacterial entry between epidermal plant cells. Although, around 25% of all legume genera are postulated to be intercellularly infected, the pathways and mechanisms supporting this process has remained virtually unexplored due to lack of genetically amenable legumes that have this infection mode. In this study, we report that the model legume Lotus japonicus is infected intercellularly by Rhizobium sp. IRBG74 and demonstrate that the resources available in Lotus enable insight into the genetic requirements and the fine-tuning of the pathway governing intercellular infection. Inoculation of Lotus mutants shows that Ern1 and RinRK1 are dispensable for intercellular infection in contrast to intracellular infection. Other symbiotic genes, including Nfr5, SymRK, CCaMK, Epr3, Cyclops, Nin, Nsp1, Nsp2, Cbs and Vpy1 are equally important for both entry modes. Comparative RNAseq analysis of roots inoculated with IRBG74 revealed a distinctive transcriptome response compared to intracellular colonization. In particular, a number of cytokinin-related genes were differentially regulated. Corroborating this observation cyp735A and ipt4 cytokinin biosynthesis mutants were significantly affected in their nodulation with IRBG74 while lhk1 cytokinin receptor mutants did not form any nodules. These results indicate that a differential requirement for cytokinin signalling conditions intercellular rhizobial entry and highlight the distinct modalities of the inter- and intra-cellular infection mechanisms.

plant biology↗

bioRxiv2020

Retrograde induction of phyB orchestrates ethylene-auxin hierarchy to regulate growth

Exquisitely regulated plastid-to-nucleus communication by retrograde signaling pathways is essential for fine-tuning of responses to the prevailing environmental conditions. The plastidial retrograde signaling metabolite methylerythritol cyclodiphosphate (MEcPP) has emerged as a stress signal transduced into a diverse ensemble of response outputs. Here we demonstrate enhanced phytochrome B protein abundance in red-light grown MEcPP-accumulating mutant (ceh1) plant relative to wild-type seedlings. We further establish MEcPP-mediated coordination of phytochrome B with auxin and ethylene signaling pathways, and uncover differential hypocotyl growth of red-light grown seedlings in response to these phytohormones. Genetic and pharmacological interference with ethylene and auxin pathways outline the hierarchy of responses, placing auxin epistatic to the ethylene signaling pathway. Collectively, our finding establishes the key role of a plastidial retrograde metabolite in orchestrating the transduction of a repertoire of signaling cascades, and positions plastids at the zenith of relaying information coordinating external signals and internal regulatory circuitry to secure organismal integrity. Two sentence summaryThe plastidial retrograde metabolite, MEcPP, orchestrates coordination of light and hormonal signaling cascade through induction of phytochrome B abundance and modulation of auxin and ethylene levels for optimal adaptive responses to light environment.

plant biology↗

bioRxiv2019

The Medicago truncatula DREPP protein triggers microtubule fragmentation in membrane nanodomains during symbiotic infections

The initiation of intracellular host cell colonization by symbiotic rhizobia in Medicago truncatula requires repolarization of root hairs, which includes the re-arrangement of cytoskeletal filaments. The molecular players governing microtubule (MT) re-organization during infection remain to be discovered. Here, we identified the M. truncatula DREPP protein and investigated its functions during rhizobial infections. We show that rhizobial colonization of drepp mutant roots as well as transgenic roots over-expressing DREPP is impaired. DREPP re-localizes into symbiosis-specific membrane nanodomains in a stimulus-dependent manner. This subcellular segregation coincides with DREPP-dependent MT fragmentation and a partial loss of the ability to re-organize the MT cytoskeleton in response to rhizobia, which might relay on an interaction between DREPP and MT organizing protein SPIRAL2 (SPR2). Taken together, our results reveal that establishment of symbiotic associations in M. truncatula require DREPP in order to regulate MT reorganization during initial root hair responses to rhizobia.

plant biology↗

bioRxiv2018

Light dynamically regulates growth rate and cellular organisation of the Arabidopsis root meristem.

1Large-scale methods and robust algorithms are needed for a quantitative analysis of cells status/geometry in situ. It allows the understanding the cellular mechanisms that direct organ growth in response to internal and environmental cues. Using advanced whole-stack imaging in combination with pattern analysis, we have developed a new approach to investigate root zonation under different dark/light conditions. This method is based on the determination of 3 different parameters: cell length, cell volume and cell proliferation on the cell-layer level. This method allowed to build a precise quantitative 3D cell atlas of the Arabidopsis root tip. Using this approach we showed that the meristematic (proliferation) zone length differs between cell layers. Considering only the rapid increase of cortex cell length to determine the meristematic zone overestimates of the proliferation zone for epidermis/cortex and underestimates it for pericycle. The use of cell volume instead of cell length to define the meristematic zone correlates better with cell proliferation zone.

plant biology↗

bioRxiv2018

Phosphorylation of the exocyst subunit Exo70B2 contributes to the regulation of its function

The exocyst is a conserved hetero-octameric complex that mediates early tethering of post-Golgi vesicles during exocytosis. Its Exo70 subunit functions as a spatiotemporal regulator by mediating numerous interactions with proteins and lipids. However, a molecular understanding of the exocyst functions remains challenging. Exo70B2 localized to dynamic foci at the plasma membrane and transited through Brefeldin A (BFA)-sensitive compartments, indicating that it participates in conventional secretion. Conversely, treatment with the immunogenic peptide flg22 or the salicylic acid (SA) defence hormone analogue Benzothiadiazole (BTH), induced Exo70B2 transport into the vacuole where it colocalized with autophagic markers AUTOPHAGY-RELATED PROTEIN 8 (ATG8) and NEIGHBOR OF BRCA1 GENE 1 (NBR1). According with its role in immunity, we discovered that Exo70B2 interacts with and is phosphorylated by the MITOGEN-ACTIVATED PROTEIN KINASE 3 (MPK3). Mimicking phosphorylation inhibited Exo70B2 localization at sites of active secretion. By contrast, lines expressing phosphonull variants displayed higher Effector-Triggered Immunity and were hypersensitive to BTH, conditions known to induce the secretory pathway. Our results suggest a molecular mechanism by which phosphorylation of Exo70B2 regulates interaction with the plasma membrane, and couples the secretory pathway with cellular signalling.

cell biology↗

bioRxiv2017

Tissue specific auxin biosynthesis regulates leaf vein patterning

The plant hormone auxin (indole-3-acetic acid, IAA) has a profound influence over plant cell growth and differentiation. Current understanding of vein development in leaves is based on the canalization of auxin into self-reinforcing streams which determine the sites of vascular cell differentiation. However, the role of auxin biosynthesis during leaf development in the context of leaf vein patterning has not been much studied so far. Here we characterize the context specific importance of auxin biosynthesis, auxin transport and mechanical regulations in a growing leaf. We show that domains of auxin biosynthesis predict the positioning of vascular cells. In mutants that have reduced capacity in auxin biosynthesis, leaf vein formation is decreased. While exogenous application of auxin does not compensate the loss of vein formation in auxin biosynthesis mutants, inhibition of polar auxin transport does compensate the vein-less phenotype, suggesting that the site-specific accumulation of auxin, which is likely to be mainly caused by the local auxin biosynthesis, is important for leaf vein formation. Our computational model of midvein development brings forth the interplay of cell stiffness and auxin dependent cell division. We propose that local auxin biosynthesis has the integral role in leaf vascular development.\n\nHighlightsO_LIBuilt spatially and temporally resolved auxin biosynthesis map in growing leaf primordium of Arabidopsis.\nC_LIO_LIExpression domains of auxin biosynthetic enzymes within primordia strongly correlated with leaf vein initiation.\nC_LIO_LIResults show that domains of auxin biosynthesis within primordia drive leaf vein initiation and patterning.\nC_LI\n\nHighlights and eTOC BlurbUsing modelling and a spatiotemporal analysis of auxin biosynthesis and transport, Kneuper et al. show that tissue specific auxin biosynthesis defines places of vein initiation hence underlining the importance of auxin concentration in vein initiation.

plant biology↗