The mucosal epithelium secretes a host of protective disulfide-rich peptides, including the trefoil factors (TFFs). The TFFs increase the viscoelasticity of the mucosa and promote cell migration, though the molecular mechanisms underlying these functions have remained poorly defined. Here, we demonstrate that all TFFs are divalent lectins that recognise the GlcNAc-α-1,4-Gal disaccharide, which terminates some mucin-like O-glycans. Degradation of this disaccharide by a glycoside hydrolase abrogates TFF binding to mucins. Structural, mutagenic and biophysical data provide insights into how the TFFs recognise this disaccharide and rationalise their ability to modulate the physical properties of mucus across different pH ranges. These data reveal that TFF activity is dependent on the glycosylation state of mucosal glycoproteins and alludes to a lectin function for trefoil domains in other human proteins.

Tryptophan C-mannosylation stabilizes proteins bearing a thrombospondin repeat (TSR) domain in metazoans. Here we show that Plasmodium falciparum expresses a DPY19 tryptophan C-mannosyltransferase in the endoplasmic reticulum and that DPY19-deficiency abolishes C-glycosylation, destabilizes members of the TRAP adhesin family and inhibits transmission to mosquitoes. Imaging P. falciparum gametogenesis in its entirety in four dimensions using lattice light-sheet microscopy reveals defects in ΔDPY19 gametocyte egress and exflagellation. While egress is diminished, ΔDPY19 microgametes still fertilize macrogametes, forming ookinetes, but these are abrogated for mosquito infection. The gametogenesis defects correspond with destabilization of MTRAP, which we show is C-mannosylated in P. falciparum, and the ookinete defect is concordant with defective CTRP secretion on the ΔDPY19 background. Genetic complementation of DPY19 restores ookinete infectivity, sporozoite production and C-mannosylation activity. Therefore, tryptophan C-mannosylation by DPY19 ensures TSR protein quality control at two lifecycle stages for successful transmission of the human malaria parasite.

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C-mannosylation stabilizes proteins bearing a thrombospondin repeat (TSR) domain in metazoans. Here we show that Plasmodium falciparum expresses a DPY19 C-mannosyltransferase in the endoplasmic reticulum and that DPY19-deficiency abolishes C-glycosylation, destabilizes members of the TRAP adhesin family and inhibits transmission to mosquitoes. P. falciparum gametogenesis was imaged in its entirety in four dimensions using lattice light-sheet microscopy. This revealed defects in egress and exflagellation for DDPY19 microgametes. While exflagellation was diminished, DDPY19 microgametes still fertilized macrogametes, forming ookinetes but these were abrogated for mosquito infection. The gametogenesis defects corresponded with destabilization of MTRAP, which we show is C-mannosylated in P. falciparum, and the ookinete defect was concordant with defective CTRP secretion on the DDPY19 background. Genetic complementation of DPY19 restored ookinete infectivity, sporozoite production and C-mannosylation activity. Therefore, tryptophan C-mannosylation by DPY19 in the early secretory pathway ensures TSR protein quality control at two lifecycle stages for successful transmission of the human malaria parasite.

Glycoside hydrolases (GHs) are a diverse group of enzymes that catalyze the hydrolysis of glycosidic bonds. The Carbohydrate-Active enZymes (CAZy) database organizes GHs into families based on sequence data and function, with fewer than 1% of the predicted proteins characterized biochemically. Consideration of genomic context can provide a useful guide to infer possible enzyme activities for proteins of unknown function. We used the MultiGeneBLAST tool to discover a putative gene cluster inMarinovumsp., a member of the marineRoseobacterclade, that encodes homologues of enzymes belonging to the sulfoquinovose monooxygenase pathway. This putative gene cluster lacks a gene encoding a classical family GH31 sulfoquinovosidase (SQase) candidate, but which instead includes an uncharacterized family GH13 protein (MsGH13). We show that recombinantMsGH13 lacks SQase activity but is a broad spectrum α-glucosidase active on a diverse array of α-linked disaccharides, including: maltose (100%), sucrose (7.9%), nigerose (52%), trehalose (20%), isomaltose (6.4%), and kojibiose (3.8%). Using AlphaFold, a 3D model for the MsGH13 enzyme was constructed that predicted its active site shared close similarity with a narrower specificity α-glucosidase fromHalomonassp. H11 of the same GH13 subfamily. This study supports recent findings that bacteria belonging to theRoseobacterclade can metabolize SQ without a classical SQase encoded in their genomes.

Esta investigación tuvo como objetivo cuantificar bacterias diazótrofas y comparar fisicoquímicamente suelos rizosféricos de tres cacaotales (Theobroma cacao L.) del Departamento Norte de Santander, Colombia; para lo cual se caracterizaron, diferenciándose en área cultivada, manejo agronómico y edad del cultivo. A partir de diluciones seriadas de las muestras y empleando la técnica de Número Más Probable (NMP), en medios de cultivo semiselectivos (NFb, JMV, LGI, JNFb) semisólidos, se cuantificaron las diazótrofas, evaluando como positivo la formación de una película subsuperficial en el medio contenido en viales sellados; muestras pares se enviaron al laboratorio Bioambiental (UNET) para los análisis fisicoquímicos. Como resultado, las muestras evaluadas mostraron deficiencias en el porcentaje de materia orgánica y elementos como Potasio, Fósforo y Magnesio. Se reportaron estadísticamente diferencias altamente significativas en NMP. La mayor cuantificación de diazótrofas se reportó en la finca Florilandia, que se caracterizó por tener riego por goteo. La mayor cuantificación de diazotrófas se registró en los medios NFb y JMV, demostrándose una mayor presencia de los presuntos géneros Azospirillum sp. y Burkholderia sp. los cuales son fácilmente aislados de suelos rizosféricos, a diferencia de los géneros Herbaspirillum sp. y Gluconacetobacter sp. que por su carácter endófito suelen ser menos predominantes en este tipo de muestras. Se concluye además, que las características fisicoquímicas del suelo, la humedad y las relaciones climáticas al momento de la toma de las muestras, condicionan la cantidad de exudados de las raíces y por tanto son factores que condicionaron la presencia de diazótrofas en las muestras.Palabras clave: Azospirillum, Burkholderia, cacao, rizósfera

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