Biology subjects

Voxeur, A.

Publications and source records attributed to Voxeur, A..

4 recordsLinked to original sources

bioRxiv2021

Impairment of the cellulose degradation machinery enhances fungal virulence but limits reproductive fitness

Fungal endophytes grow in the apoplastic space, in constant contact with the plant cell wall (CW) that hinders microbe progression, while representing a source of nutrients. Although numerous fungal CW modifying proteins have been identified, their role during host colonization remains underexplored. Here we show that the root-infecting plant pathogen Fusarium oxysporum (Fo) does not require its complete arsenal of cellulases to infect the host plant. Quite the opposite, Fo mutants impaired in cellulose degradation become hypervirulent by enhancing the secretion of virulence factors. On the other hand, the reduction on cellulase activity had a severe negative effect on saprophytic growth and microconidia production during the final stages of the Fo infection cycle. These findings enhance our understanding on the function of plant CW degradation on the outcome of host-microbe interactions and reveal an unexpected role of cellulose degradation in a pathogens evolutionary success. TeaserUnexpectedly, fungi compromised in their capacity to degrade plant cellulose are hypervirulent but impaired in sporulation.

microbiology↗

bioRxiv2021

Pectin remodeling belongs to a homeostatic system and triggers transcriptomic and hormonal modulations

O_LIHere, we focused on the biological modifications arisen from a strong and transient variation of the pectin methylesterification status during the seed-to-seedling transition. C_LIO_LIA reverse genetic approach was used to trigger specific reduction of pectin de-methylesterification during the seed maturation stage and the related physiological effects were assessed using a combination of biochemical, transcriptomic and microscopic analyses. C_LIO_LIArabidopsis PME36 is required to implement the characteristic pattern of de-methylesterified pectin in the mature seed. While this pattern is strongly impaired in pme36-1 and pme36-2 mature seed, no phenotypical effect is observed in the knockout mutant during seed germination. By analyzing hormone homeostasis and gene expression regulation, we show a strong and dynamic physiological disorder in the mutant, which reveals the existence of a complex compensatory mechanism overcoming the defect in pectin de-methylesterification. C_LIO_LIOur results reveal that pectin methylesterification status acts as upstream modulator involved in an undescribed homeostatic system in which pectin remodeling, hormone signaling and transcriptomic regulations interact to ensure the maintenance of a normal seed-to-seedling developmental program. C_LI

plant biology↗

bioRxiv2021

Plant inositol-phosphate-glycans and fucosylated xyloglucan oligosaccharide are accumulated upon Arabidopsis thaliana/ Botrytis cinerea infection

In mammals, insulin is involved in controlling blood glucose levels and its role in modulating immunity is being more and more documented. This hormone promotes the release of inositolphosphate glycans (IPG) which act as mediators. In plants, one IG has already been identified in plant culture cells (Smith and Fry, 1999; Smith et al., 1999) but, to our knowledge, no IPG have been yet identified. Here, we discovered 7 IPG that are accumulated upon Arabidopsis thaliana-Botrytis cinerea interaction, concomitantly with oligogalacturonides and a fucosylated xyloglucan oligosaccharide. Further structural characterization showed that they come from the hydrolysis of polar heads of Serie A to H glycosylinositol phosphorylceramides presumably via a phospholipase C activity. Taken together with the emerging role of insulin as immune regulator, these results question the role of IPG as damage associated molecular pattern both in animal and plant kingdoms.

plant biology↗

bioRxiv2021

The pH-dependent processivity of Arabidopsis AtPME2 can control cell wall mechanical properties

Pectin methylesterases (PMEs) modify homogalacturonans (HG) chemistry and play a key role in regulating primary cell wall mechanical properties. How PME activity can fine-tune pectin structure in the growing plant has remained elusive. Here we report on the Arabidopsis AtPME2, which we found to be highly expressed during lateral root emergence and dark-grown hypocotyl elongation. We produced the mature active enzyme using heterologous expression in Pichia pastoris and characterized it through the use of a generic plant PME antiserum suitable for detecting recombinant and native enzyme independent of species source. At neutral pH AtPME2 is preferentially active on pectins with a degree of 55-70% methylesterification and can be inhibited by PME inhibitor protein (PMEI). We show that the mode of action for AtPME2 can switch from full processivity (at pH 8), creating large blocks of unmethylated galacturonic acid, to low processivity (at pH 5) and relate these observations to the differences in electrostatic potential of the protein at acidic and alkaline pH. To assess the role of AtPME2 in development, we characterized two knock-out lines. We show that in the context of acidified apoplast, low-processive demethylesterification by AtPME2 can loosen the cell wall, with consequent increase in cell elongation and etiolated hypocotyl length. Our study brings insights into how the pH-dependent regulation by PME activity could affect pectin structure and associated cell wall mechanical properties in expansion. One sentence summaryThe processivity of AtPME2, a pectin methylesterase that fine-tunes cell wall pectins is modulated by pH in vitro and impacts the mechanical properties of the wall, affecting development in planta.

plant biology↗