Biology subjects

Pottier, M.

Publications and source records attributed to Pottier, M..

5 recordsLinked to original sources

bioRxiv2024

Identification of nuclear pore proteins at plasmodesmata

Plasmodesmata (PD) mediate intercellular exchange of small molecules, RNAs and proteins between plant cells with an apparent exclusion limit for passive non-specific transport, and transport of specific cargo mediated by mediators. PD and nuclear pore complexes (NPC) are nanometer sized micropores with strikingly similar properties. Cargo translocation through NPC is mediated by phase separating FG-nucleoporins (FG-NUP). Here, bioinformatics, proteomics and fluorescence imaging identified FG-NUPs at PD. Transient expression of GFP fusions at low and intermediate expression levels supported dual localization of 12 NUPs to NPC and PD. Structured illumination microscopy detected the transmembrane anchor NUP CPR5 close to orifices of PD. cpr5 mutants showed reduced intercellular short-root (SHR) transport. However, transport defects cannot be excluded due to indirect effects in the mutants. Identification of FG-NUPs at PD is consistent with the recruitment of NUPs to form a PD pore gating complex consistent with phase separation domains as diffusion barriers at PD. Further analyses will be required to determine whether NUPs are bona fide PD components, or accumulate at PD in certain conditions, or may serve intermediate NPC storage.

cell biology↗

bioRxiv2022

A high confidence Physcomitrium patens plasmodesmata proteome by iterative scoring and validation reveals diversification of cell wall proteins during evolution

Cells of multicellular organisms exchange nutrients, building blocks and information. In animals, this happens via gap junctions, in plants via plasmodesmata (PD). PD have striking properties, translocating a large range of molecules from ions, to metabolites, RNA and proteins up to 40 kDa. PD are hard to characterize due to being deeply embedded into cell walls and the presence of several membranes. While previous studies of protein composition of PD from angiosperms identified large lists of proteins, few were validated. Here, we developed a PD scoring approach in conjunction with systematic localization on a large scale to define a high-confidence PD proteome of Physcomitrium patens. This high confidence PD proteome comprises nearly 300 proteins, which together with the bona fide PD proteins from literature, are made available in the public PDDB database. Conservation of localization across plant species strengthens the reliability of plant PD proteomes and provides a basis for exploring the evolution of this important organelle. In particular, the P. patens PD proteome was highly enriched in cell wall modifying proteins. Callose-degrading glycolyl hydrolase family 17 (GHL17) proteins are presented as an abundant PD protein family with representatives across an evolutionary scale. Exclusively members of the alpha-clade of the GHL17 family are shown to be PD localized and their orthologs occur only in plant species which have developed PD. Members of the EXORDIUM-family and xyloglucan transglycosylases are additional cell-wall located proteins highly abundant in the P. patens PD proteome also showing evolutionary diversification of PD localized family members from other clade members.

plant biology↗

bioRxiv2021

Duplication of NRAMP3 gene in poplars generated two homologous transporters with distinct functions

Transition metals are essential for a wealth of metabolic reactions, but their concentrations need to be tightly controlled across cells and cell compartments, as metal excess or imbalance has deleterious effects. Metal homeostasis is achieved by a combination of metal transport across membranes and metal binding to a variety of molecules. Gene duplication is a key process in evolution, as emergence of advantageous mutations on one of the copies can confer a new function. Here, we report that the poplar genome contains two paralogues encoding NRAMP3 metal transporters localized in tandem. All Populus species analyzed had two copies of NRAMP3, whereas only one could be identified in Salix species indicating that duplication occurred when the two genera separated. Both copies are under purifying selection and encode functional transporters, as shown by expression in the yeast heterologous expression system. However, genetic complementation revealed that only one of the paralogues has retained the original function in release of metals stored in the vacuole previously characterized in A. thaliana. Confocal imaging showed that the other copy has acquired a distinct localization to the Trans Golgi Network (TGN). Expression in poplar suggested that the copy of NRAMP3 localized on the TGN has a novel function in the control of cell-to-cell transport of manganese. This work provides a clear case of neo-functionalization through change in the subcellular localization of a metal transporter as well as evidence for the involvement of the secretory pathway in cell-to-cell transport of manganese.

evolutionary biology↗

bioRxiv2019

Unveiling two new trichome-specific promoters of interest for metabolic engineering in Nicotiana tabacum

Main conclusion pRbcS-T1 and pMALD1, two new trichome-specific promoters of Nicotiana tabacum, were identified and their strength and specificity were compared to those of previously described promoters in this species. Nicotiana tabacum has emerged as a suitable host for metabolic engineering of terpenoids and derivatives in tall glandular trichomes, which actively synthesize and secrete specialized metabolites. However, implementation of an entire biosynthetic pathway in glandular trichomes requires the identification of trichome-specific promoters to appropriately drive the expression of the transgenes needed to set up the desired pathway. In this context, RT-qPCR analysis was carried out on wild-type N. tabacum plants to compare the expression pattern and gene expression level of NtRbcS-T1 and NtMALD1, two newly identified genes expressed in glandular trichomes, with those of NtCYP71D16, NtCBTS2, NtCPS2, and NtLTP1, which were reported in the literature to be specifically expressed in glandular trichomes. We show that NtRbcS-T1 and NtMALD1 are specifically expressed in glandular trichomes like NtCYP71D16, NtCBTS2, and NtCPS2, while NtLTP1 is also expressed in other leaf tissues as well as in the stem. Transcriptional fusions of each of the six promoters to the GUS-VENUS reporter gene were introduced in N. tabacum by Agrobacterium-mediated transformation. Almost all transgenic lines displayed GUS activity in tall glandular trichomes, indicating that the appropriate cis regulatory elements were included in the selected promoter regions. However, unlike for the other promoters, no trichome-specific line was obtained for pNtLTP1:GUS-VENUS, thus in agreement with the RT-qPCR data. These data thus provide two new transcription promoters that could be used in metabolic engineering of glandular trichomes.

plant biology↗

bioRxiv2018

Autophagy is essential for optimal Fe translocation to seeds in Arabidopsis

Micronutrient deficiencies affect a large part of the world population. They are mostly due to the consumption of grains with insufficient content of Fe or Zn. Both de novo uptake by roots and recycling from leaves may provide seeds with nutrients. Autophagy, which is a conserved mechanism for nutrient recycling in eukaryotes, was shown to be involved in nitrogen remobilization to seeds. Here, we have investigated the role of this mechanism in micronutrient translocation to seeds. We found that several Arabidopsis thaliana plants impaired in autophagy display defects in nutrient remobilization to seeds. In atg5-1 mutant, which is completely defective in autophagy, the efficiency of Fe translocation from vegetative organs to seeds was severely decreased even when Fe was provided during seed formation. Combining atg5-1 with sid2 mutation that counteracts premature senescence associated to autophagy deficiency and using 57Fe pulse labeling, we could propose a two-step mechanism in which iron taken up de novo during seed formation is first accumulated in vegetative organs and subsequently remobilized to seeds. Finally, we showed that translocations of zinc and manganese to seeds are also dependent on autophagy. Fine tuning autophagy during seed formation opens therefore new possibilities to improve micronutrient remobilization to seeds.

plant biology↗