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Chitin
About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.
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TL;DR: The results suggest that the myosin motor domain of ChsV supports exocytosis but not long-range delivery of transport vesicles, and it is demonstrated that both domains are required for fungal virulence.
Abstract: Class V chitin synthases are fungal virulence factors required for plant infection. They consist of a myosin motor domain fused to a membrane-spanning chitin synthase region that participates in fungal cell wall formation. The function of the motor domain is unknown, but it might deliver the myosin chitin synthase-attached vesicles to the growth region. Here, we analyze the importance of both domains in Mcs1, the chitin synthase V of the maize smut fungus Ustilago maydis. By quantitative analysis of disease symptoms, tissue colonization, and single-cell morphogenic parameters, we demonstrate that both domains are required for fungal virulence. Fungi carrying mutations in the chitin synthase domain are rapidly recognized and killed by the plant, whereas fungi carrying a deletion of the motor domain show alterations in cell wall composition but can invade host tissue and cause a moderate plant response. We also show that Mcs1-bound vesicles exhibit long-range movement for up to 20 mm at a velocity of ;1.75 mm/s. Apical Mcs1 localization depends on F-actin and the motor domain, whereas Mcs1 motility requires microtubules and persists when the Mcs1 motor domain is deleted. Our results suggest that the myosin motor domain of ChsV supports exocytosis but not long-range delivery of transport vesicles.
78 citations
TL;DR: It is suggested that CHS4 may serve as an auxiliary enzyme in N. crassa and that, in contrast to yeasts, it is possible that filamentous fungi may have more than one class IV chitin synthase.
Abstract: In Saccharomyces cerevisiae, most of the cel- lular chitin is produced by chitin synthase III, which requires the product encoded by the CSD2/CAL1/ DIT101/KT12 gene. We have identified, isolated and structurally characterized a CSD2/CAL1/DIT101/KT12 homologue in the filamentous ascomycete Neurospora crassa and have used a ''reverse genetics'' approach to determine its role in vivo. The yeast gene was used as a heterologous probe for the isolation of a N. crassa gene (designated chs-4) encoding a polypeptide belong- ing to a class of chitin synthases which we have desig- nated class IV. The predicted polypeptide encoded by this gene is highly similar to those of S. cerevisiae and Candida albicans. N. crassa strains in which chs-4 had been inactivated by the Repeat-Induced Point muta- tion (RIP) process grew and developed in a normal manner under standard growth conditions. However, when grown in the presence of sorbose (a carbon source which induces morphological changes accompanied by elevated chitin content), chitin levels in the chs-4RIP strain were significantly lower than those observed in the wild type. We suggest that CHS4 may serve as an auxiliary enzyme in N. crassa and that, in contrast to yeasts, it is possible that filamentous fungi may have more than one class IV chitin synthase.
77 citations
TL;DR: Thirty-seven species of marine invertebrates from different systematic and ecological position were quantitatively tested for cellulase and chininase activity in their digestive systems, and Ascidia Halocyntia aurantium and Metridium senile fimbriatum were found to possess the highest chitin enzyme activity.
Abstract: 1. 1. Thirty-seven species of marine invertebrates from different systematic and ecological position were quantitatively tested for cellulase and chininase activity in their digestive systems. 2. 2. Enzymes were tested by several methods. Carboxymethlcellulase (CMC-ase) and carboxymethylchitinase (CMCh-ase) activities were estimated by the decrease in viscosity of these solutions and by the increase of the reducing sugars. Chitinase activity by precipitated chitin (PCh) was tested by the simultaneous measurement of the reducing sugar (RS) and N-acetylglucosamine (NAGA) in an incubation mixture and by chitin (Ch), using the last method only. 3. 3. Ascidia Halocyntia aurantium and Metridium senile fimbriatum were found to possess the highest chitinase activity; mollusca Littorina mandschurica and L. brevicula had the highest cellulase activity.
77 citations
TL;DR: Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function.
Abstract: Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-D-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.
77 citations
TL;DR: The results suggest that Chs8p synthesized the long‐chitin microfibrils, and Chs3p synthesizes the short‐ch itin rodlets at the same cellular location, which suggests the architecture of the chitin skeleton of C.’albicans is shaped by the action of more than one chit in synthase at the site of cell wall synthesis.
Abstract: The shape and integrity of fungal cells is dependent on the skeletal polysaccharides in their cell walls of which β(1,3)-glucan and chitin are of principle importance. The human pathogenic fungus Candida albicans has four genes, CHS1, CHS2, CHS3 and CHS8, which encode chitin synthase isoenzymes with different biochemical properties and physiological functions. Analysis of the morphology of chitin in cell wall ghosts revealed two distinct forms of chitin microfibrils: short microcrystalline rodlets that comprised the bulk of the cell wall; and a network of longer interlaced microfibrils in the bud scars and primary septa. Analysis of chitin ghosts of chs mutant strains by shadow-cast transmission electron microscopy showed that the long-chitin microfibrils were absent in chs8 mutants and the short-chitin rodlets were absent in chs3 mutants. The inferred site of chitin microfibril synthesis of these Chs enzymes was corroborated by their localization determined in Chsp–YFP-expressing strains. These results suggest that Chs8p synthesizes the long-chitin microfibrils, and Chs3p synthesizes the short-chitin rodlets at the same cellular location. Therefore the architecture of the chitin skeleton of C. albicans is shaped by the action of more than one chitin synthase at the site of cell wall synthesis.
77 citations