Biology subjects

Le Gall, S.

Publications and source records attributed to Le Gall, S..

3 recordsLinked to original sources

bioRxiv2024

Receptor kinase LecRK-I.9 regulates cell wall remodelling and signalling during lateral root formation in Arabidopsis

Assembling and remodelling the cell wall is essential for plant development. Cell wall dynamic is controlled by cell wall proteins and a variety of sensor and receptor systems. LecRK-I.9, an Arabidopsis thaliana plasma membrane-localised lectin receptor kinase, was previously shown to be involved in cell wall-plasma membrane contacts and to play roles in plant-pathogen interactions, but so far, its role in development was unknown. LecRK-I.9 is transcribed at a high level in root tissues including the pericycle. Comparative transcript profiling of a loss-of-function mutant vs wild type identifies LecRK-I.9 as a regulator of cell wall metabolism. Consistently, lecrk-I.9 mutants display an increased pectin methylesterification level correlated with decreased pectin methylesterase and increased polygalacturonase activities. Also, LecRK-I.9 impacts lateral root development through the regulation of genes encoding (i) cell wall remodelling proteins during early events of lateral root initiation, and (ii) cell wall signalling peptides (CLE2, CLE4) repressing lateral root emergence and growth. Besides, low nitrate reduces LecRK-I.9 expression in pericycle and interferes with its regulatory network: however, the control of CLE2 and CLE4 expression is maintained. Altogether, the results show that LecRK-I.9 is a key player in a signalling network regulating both pre-branch site formation and lateral root emergence. HighlightThe lectin receptor kinase LecRK-I.9 regulates the molecular events leading to lateral root formation in both the initiation and emergence processes in Arabidopsis through cell wall remodelling enzymes and signalling peptides.

plant biology↗

bioRxiv2023

Development and calibration of the FSPM CPlantBox to represent the interactions between water and carbon fluxes in the soil-plant-atmosphere continuum

A plants development is strongly linked to the water and carbon flows in the soil-plant-atmosphere continuum. Expected climate shifts will alter the water and carbon cycles and will affect plant phenotypes. Comprehensive models which simulate mechanistically and dynamically the feedback loops between a plants three-dimensional development and the water and carbon flows are useful tools to evaluate the sustainability of genotype-environment-management combinations which do not yet exist. In this study, we present the latest version of the open-source three-dimensional Functional-Structural Plant Model CPlantBox with PiafMunch and DuMux coupling. We simulated semi-mechanistically the development of generic C3 monocots from 10 to 25 days after sowing and undergoing an atmospheric dry spell of one week (no precipitation). We compared the results for dry spells starting on different days (day 11 or 18) and with different climates (wetter and colder against drier and warmer atmospheric and initial soil conditions). Compared with the wetter and colder climate, the dry spell with the drier and warmer climate led to a lower instantaneous water use efficiency. Moreover, the lower symplasm turgor for the drier and warmer climate limited the growth, which made the sucrose available for other processes, such as maintenance respiration. Both of these effects were stronger for the later dry spell compared with the early dry spell under the drier and warmer climate. We could thus use CPlantBox to simulate diverging emerging processes (like carbon partitioning) defining the plants phenotypic plasticity response to their environment.

plant biology↗

bioRxiv2022

The maize pathogen Ustilago maydis secretes glycoside hydrolases and carbohydrate oxidases directed towards components of the fungal cell wall

Filamentous fungi are keystone microorganisms in the regulation of many processes occurring on Earth, such as plant biomass decay, pathogenesis as well as symbiotic associations. In many of these processes, fungi secrete carbohydrate-active enzymes (CAZymes) to modify and/or degrade carbohydrates. Ten years ago, while evaluating the potential of a secretome from the maize pathogen Ustilago maydis to supplement lignocellulolytic cocktails, we noticed it contained many unknown or poorly characterized CAZymes. Here, and after re-annotation of this dataset and detailed phylogenetic analyses, we observed that several CAZymes (including glycoside hydrolases and carbohydrate oxidases) are predicted to act on the fungal cell wall (FCW), notably on {beta}-1,3-glucans. We heterologously produced and biochemically characterized two new CAZymes, called UmGH16_1-A and UmAA3_2-A. We show that UmGH16_1-A displays {beta}-1,3-glucanase activity, with a preference for {beta}-1,3-glucans with short {beta}-1,6 substitutions, and UmAA3_2-A is a dehydrogenase catalyzing the oxidation of {beta}-1,3- and {beta}-1,6-gluco-oligosaccharides into the corresponding aldonic acids. Working on model {beta}-1,3-glucans, we show that the linear oligosaccharide products released by UmGH16_1-A are further oxidized by UmAA3_2-A, bringing to light a putative biocatalytic cascade. Interestingly, analysis of available transcriptomics data indicates that both UmGH16_1-A and UmAA3_2-A are co-expressed, only during early stages of U. maydis infection cycle. Altogether, our results suggest that both enzymes are connected and that additional accessory activities still need to be uncovered to fully understand the biocatalytic cascade at play and its physiological role. ImportanceFilamentous fungi play a central regulatory role on Earth, notably in the global carbon cycle. Regardless of their lifestyle, filamentous fungi need to remodel their own cell wall (mostly composed of polysaccharides) to grow and proliferate. To do so, they must secrete a large arsenal of enzymes, most notably carbohydrate-active enzymes (CAZymes). However, research on fungal CAZymes over past decades has mainly focused on finding efficient plant biomass conversion processes while CAZymes directed at the fungus itself have remained little explored. In the present study, using the maize pathogen Ustilago maydis as model, we set off to evaluate the prevalence of CAZymes directed towards the fungal cell wall during growth of the fungus on plant biomass and characterized two new CAZymes active on fungal cell wall components. Our results suggest the existence of a biocatalytic cascade that remains to be fully understood.

biochemistry↗