The transition from the vegetative to the sexual cycle in filamentous ascomycetes is initiated with the formation of ascogonia. Here, we describe a novel type of sterile mutant from Sordaria macrospora with a defect in ascogonial septum formation. This mutant, named pro22, produces only small, defective protoperithecia and carries a point mutation in a gene encoding a protein that is highly conserved throughout eukaryotes. Sequence analyses revealed three putative transmembrane domains and a C-terminal domain of unknown function. Live-cell imaging showed that PRO22 is predominantly localized in the dynamic tubular and vesicular vacuolar network of the peripheral colony region close to growing hyphal tips and in ascogonia; it is absent from the large spherical vacuoles in the vegetative hyphae of the subperipheral region of the colony. This points to a specific role of PRO22 in the tubular and vesicular vacuolar network, and the loss of intercalary septation in ascogonia suggests that PRO22 functions during the initiation of sexual development.The formation of fruiting bodies in filamentous ascomycetes is a process of multicellular differentiation controlled by many developmentally regulated genes. The self-fertile ascomycete Sordaria macrospora represents an excellent model for studying cell differentiation during fungal fruiting body development (reviewed in references 9 and 24).During the life cycle of S. macrospora, a mature haploid ascospore germinates and produces a mycelium composed of multinucleate hyphal compartments. After 2 to 3 days, coiled female reproductive hyphae, called ascogonia, are formed. Each ascogonium develops further into a more-or-less spherical protoperithecium composed of pseudoparenchymatous tissue surrounding the original ascogonium (24, 47). Ascogenous hyphae emerge from the ascogonium inside the protoperithecium. Within the ascogenous hyphae, the nuclei pair up to form the dikaryotic state, even though S. macrospora is selffertile and does not require fertilization with an opposite mating type (11,49). The transition from the spherical protoperithecial to the flask-shaped perithecial stage, is believed to be stimulated by the formation of the dikaryon, although this has not been experimentally verified (24). The dikaryotic state in individual hyphal compartments of the growing ascogenous hyphae is maintained by precisely orchestrated crozier formation from the tip of an ascogenous hypha, fusion of the crozier tip with the penultimate cell of the ascogenous hypha, conjugate mitotic divisions, and highly regulated septation (50, 69). Karyogamy of two nuclei in the penultimate cell results in the formation of a diploid ascus mother cell. The diploid state is very short-lived because the diploid nuclei which are formed immediately undergo meiosis, followed by an extra mitotic division resulting in an ascus containing eight haploid ascospores (11,49). An identical process has been observed in the heterothallic fungus Neurospora crassa, with the exception that cell fusion between opposit...

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In order to produce multicellular structures filamentous fungi combine various morphogenetic programs that are fundamentally different from those used by plants and animals. The perithecium, the female sexual fruitbody of Neurospora crassa, differentiates from the vegetative mycelium in distinct morphological stages, and represents one of the more complex multicellular structures produced by fungi. In this study we defined the stages of protoperithecial morphogenesis in the N. crassa wild type in greater detail than has previously been described; compared protoperithecial morphogenesis in gene-deletion mutants of all nine mitogen-activated protein (MAP) kinases conserved in N. crassa; confirmed that all three MAP kinase cascades are required for sexual development; and showed that the three different cascades each have distinctly different functions during this process. However, only MAP kinases equivalent to the budding yeast pheromone response and cell wall integrity pathways, but not the osmoregulatory pathway, were essential for vegetative cell fusion. Evidence was obtained for MAP kinase signaling cascades performing roles in extracellular matrix deposition, hyphal adhesion, and envelopment during the construction of fertilizable protoperithecia.

We study the films formed by tetradecylamine (TDA) at the water-dodecane interface in the presence of hydrogen phosphate ions. Using Fourier transform infrared spectroscopy (FTIR), interfacial shear rheology, confocal fluorescence microscopy, cryo-scanning electron microscopy (cryo-SEM), and small-angle neutron scattering (SANS), we find that between pH 5 and 8 tetradecylammonium cations bind to hydrogen phosphate anions to form needle-shaped crystallites of tetradecylammonium hydrogen phosphate (TAHP). These crystallites self-assemble into films with a range of morphologies; below pH 7, they form brittle, continuous sheets, and at pH 8, they form lace-like networks that deform plastically under shear. They are also temperature-responsive: when the system is heated, the film thins and its rheological moduli drop. We find that the temperature response is caused by dissolution of the film in to the bulk fluid phases. Finally, we show that these films can be used to stabilize temperature-responsive water-in-oil emulsions with potential applications in controlled release of active molecules.