Analysis of exocyst function in endodermis reveals its widespread contribution and specificity of action

The exocyst is the main plasma membrane vesicle-tethering complex in eukaryotes and is composed of eight different subunits. Yet, in plant genomes, many subunits display multiple copies, thought to reflect evolution of complex subtypes with divergent functions. In Arabidopsis thaliana root endodermal cells, the isoform EXO70A1 is required for positioning of CASP1 at the Casparian Strip Domain, but not for its non-targeted secretion to the plasma membrane. Here, we show that exo84b resembles exo70a1 mutants regarding CASP1 mistargeting and secretion of apoplastic proteins, but exo84b additionally affects secretion of other integral plasma membrane proteins. Moreover, conditional, cell-type-specific gene editing of the single-copy core component SEC6 allows visualization of secretion defects in plant cells with a complete lack of exocyst complex function. Our approach opens avenues for deciphering the complexity/diversity of exocyst functions in plant cells and enables analysis of central trafficking components with lethal phenotypes. Genetic analysis of exocyst isoforms reveals their distinct roles in cargo secretion.Peer reviewe

Plant cell wall patterning and expansion mediated by protein-peptide-polysaccharide interaction

Assembly of cell wall polysaccharides into specific patterns is required for plant growth. A complex of RAPID ALKALINIZATION FACTOR 4 (RALF4) and its cell wall-anchored LEUCINE-RICH REPEAT EXTENSIN 8 (LRX8)-interacting protein is crucial for cell wall integrity during pollen tube growth, but its molecular connection with the cell wall is unknown. Here, we show that LRX8-RALF4 complexes adopt a heterotetrametric configuration in vivo, displaying a dendritic distribution. The LRX8-RALF4 complex specifically interacts with demethylesterified pectins in a charge-dependent manner through RALF4's polycationic surface. The LRX8-RALF4-pectin interaction exerts a condensing effect, patterning the cell wall's polymers into a reticulated network essential for wall integrity and expansion. Our work uncovers a dual structural and signaling role for RALF4 in pollen tube growth and in the assembly of complex extracellular polymers

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

CASP microdomain formation requires cross cell wall stabilization of domains and non-cell autonomous action of LOTR1.

Efficient uptake of nutrients in both animal and plant cells requires tissue-spanning diffusion barriers separating inner tissues from the outer lumen/soil. However, we poorly understand how such contiguous three-dimensional superstructures are formed in plants. Here, we show that correct establishment of the plant Casparian Strip (CS) network relies on local neighbor communication. We show that positioning of Casparian Strip membrane domains (CSDs) is tightly coordinated between neighbors in wild-type and that restriction of domain formation involves the putative extracellular protease LOTR1. Impaired domain restriction in lotr1 leads to fully functional CSDs at ectopic positions, forming 'half strips'. LOTR1 action in the endodermis requires its expression in the stele. LOTR1 endodermal expression cannot complement, while cortex expression causes a dominant-negative phenotype. Our findings establish LOTR1 as a crucial player in CSD positioning acting in a directional, non-cell-autonomous manner to restrict and coordinate CS positioning

PHO1 family members transport phosphate from infected nodule cells to bacteroids in Medicago truncatula

International audienceLegumes play an important role in the soil nitrogen availability via symbiotic nitrogen fixation (SNF). Phosphate (Pi) deficiency severely impacts SNF because of the high Pi requirement of symbiosis. Whereas PHT1 transporters are involved in Pi uptake into nodules, it is unknown how Pi is transferred from the plant infected cells to nitrogen-fixing bacteroids. We hypothesized that Medicago truncatula genes homologous to Arabidopsis PHO1, encoding a vascular apoplastic Pi exporter, are involved in Pi transfer to bacteroids. Among the seven MtPHO1 genes present in M. truncatula, we found that two genes, namely MtPHO1.1 and MtPHO1.2, were broadly expressed across the various nodule zones in addition to the root vascular system. Expressions of MtPHO1.1 and MtPHO1.2 in Nicotiana benthamiana mediated specific Pi export. Plants with nodule-specific downregulation of both MtPHO1.1 and MtPHO1.2 were generated by RNA interference (RNAi) to examine their roles in nodule Pi homeostasis. Nodules of RNAi plants had lower Pi content and a three-fold reduction in SNF, resulting in reduced shoot growth. Whereas the rate of 33Pi uptake into nodules of RNAi plants was similar to control, transfer of 33Pi from nodule cells into bacteroids was reduced and bacteroids activated their Pi-deficiency response. Our results implicate plant MtPHO1 genes in bacteroid Pi homeostasis and SNF via the transfer of Pi from nodule infected cells to bacteroids

Mutual recognition of parental and F1 lymphocytes. Selective abrogation of eytotoxic potential of FI lymphoeytes by parental lymphocytes.J. Exp. Med

The injection of F1 hybrid animals with parental spleen or lymph node cells leads to the activation of specific parental lymphocytes which recognize major histocompatibility complex (MHC) 1-coded antigens of the other parental haplotype expressed by the F1 host (1). Such recognition can result in graft-vs.-host (GVH) reactions which are frequently associated with depressed in vivo cell-mediated immune functions, such as resistance to bacterial infection (2), skin graft rejection (2, 3), T-helper cell dysfunction (4), as well as antibody responses to thymic-dependent and-independent antigens (5-8). The depression of T-cell-mediated lympholysis (CML) responses by cells from F1 hybrid mice injected with parental lymphocytes has not been reported but could provide a useful approach for investigating T-cell receptors because self MHC-restricted as well as allogeneic CML responses can be analyzed. This report describes an experimental system in which intravenous injection of F1 hybrid mice with parental T-splenic lymphocytes can result in the abrogation or severe depression of CML potential. This loss of CML activity did not appear to be specific for self determinants because responses to alloantigens, trinitrophenyl (TNP)modified F1 cells (TNP-self), and TNP-modified parental cells were all affected. However, an unexpected finding was the observation that the parental-induced CML depression was dependent upon the H-2 type of the injected parental lymphocytes. Thus, the injection of H-2 a, H-2 k, or H-2 a, but not H-2 6, parental lymphocytes resulted in depressed CML potential. These findings are discussed with respect to (a) the selective resistance of F1 mice to H-2 b parental lymphocytes, and (b) the possibility that Fa lymphocytes recognize idiotypic determinants specific for non-H-2 b antigens on H-2 b lymphocytes, but not those for H-2 b antigens on non-H-2 b lymphocytes

Deletion of the serine protease CAP2/Tmprss4 leads to dysregulated renal water handling upon dietary potassium depletion

International audienc

GDSL-domain proteins have key roles in suberin polymerization and degradation

Plant roots acquire nutrients and water while managing interactions with the soil microbiota. The root endodermis provides an extracellular diffusion barrier through a network of lignified cell walls called Casparian strips, supported by subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, suberin lamellae display plasticity, which is crucial for root adaptative responses. Although suberin is a major plant polymer, fundamental aspects of its biosynthesis and turnover have remained obscure. Plants shape their root system via lateral root formation, an auxin-induced process requiring local breaking and re-sealing of endodermal lignin and suberin barriers. Here, we show that differentiated endodermal cells have a specific, auxin-mediated transcriptional response dominated by cell wall remodelling genes. We identified two sets of auxin-regulated GDSL lipases. One is required for suberin synthesis, while the other can drive suberin degradation. These enzymes have key roles in suberization, driving root suberin plasticity

ABCG transporters export cutin precursors for the formation of the plant cuticle

International audienceThe plant cuticle is deposited on the surface of primary plant organs, such as leaves, fruits, and floral organs,forming a diffusion barrier and protecting the plant against various abiotic and biotic stresses. Cutin, thestructural polyester of the plant cuticle, is synthesized in the apoplast. Plasma-membrane-localized ATP-binding cassette (ABC) transporters of the G family have been hypothesized to export cutin precursors.Here, we characterizeSlABCG42of tomato representing an ortholog ofAtABCG32inArabidopsis.SlABCG42expression inArabidopsiscomplements the cuticular deficiencies of theArabidopsis pec1/abcg32mutant.RNAi-dependent downregulation of both tomato genes encoding proteins highly homologous to AtABCG32(SlABCG36 and SlABCG42) leads to reduced cutin deposition and formation of a thinner cuticle in tomatofruits. By using a tobacco (Nicotiana benthamiana) protoplast system, we show that AtABCG32 andSlABCG42 have an export activity for 10,16-dihydroxy hexadecanoyl-2-glycerol, a cutin precursorin vivo.Interestingly, also freeu-hydroxy hexadecanoic acid as well as hexadecanedioic acid were exported,furthering the research on the identification of cutin precursorsin vivoand the respective mechanisms of their integration into the cutin polymer