Biology subjects

Ditengou, F. A.

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

3 recordsLinked to original sources

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↗