Amino acid divergence between the CHS domain contributes to the different intracellular behaviour of Family II fungal chitin synthases in Saccharomyces cerevisiae

Dye stability of black cherry plum anthocyanins in the interaction with co-pigments and sucrose sweetener

In this research, the co-pigmentation reactions between black cherry plum (Prunus cerasifera Ehrh. cv. Pissardii Nigra) anthocyanins and caffeic, gallic, 4-hydroxybenzoic, malic, and tannic acids with different concentrations (0, 120, 240, 480, and 960 mg L-1) at various temperatures (20, 40, 60, 80, and 100°C) were investigated at pH 3.5. The strongest immediate co-pigmentations resulted at 960 mg L-1, being significantly highest using tannic acid at all temperatures. In addition, the anthocyanin stability and the brown polymeric color formation were investigated in the presence of different concentrations of sucrose sweetener (0, 30, and 60%) and different pHs (2 and 3) in the range of 0-60 h. Also, the amount of furfural was measured in the presence of 0% and 30% sucrose concentrations at pH 2 after 20 h at 90°C by HPLC (high-performance liquid chromatography), and the most polymeric color formation was observed in the concentration of 60% sucrose at pH 2 after 60 h.

The Functional Specialization of Exomer as a Cargo Adaptor During the Evolution of Fungi

Yeast exomer is a heterotetrameric complex that is assembled at the trans-Golgi network, which is required for the delivery of a distinct set of proteins to the plasma membrane using ChAPs (Chs5-Arf1 binding proteins) Chs6 and Bch2 as dedicated cargo adaptors. However, our results show a significant functional divergence between them, suggesting an evolutionary specialization among the ChAPs. Moreover, the characterization of exomer mutants in several fungi indicates that exomer's function as a cargo adaptor is a late evolutionary acquisition associated with several gene duplications of the fungal ChAPs ancestor. Initial gene duplication led to the formation of the two ChAPs families, Chs6 and Bch1, in the Saccaromycotina group, which have remained functionally redundant based on the characterization of Kluyveromyces lactis mutants. The whole-genome duplication that occurred within the Saccharomyces genus facilitated a further divergence, which allowed Chs6/Bch2 and Bch1/Bud7 pairs to become specialized for specific cellular functions. We also show that the behavior of S. cerevisiae Chs3 as an exomer cargo is associated with the presence of specific cytosolic domains in this protein, which favor its interaction with exomer and AP-1 complexes. However, these domains are not conserved in the Chs3 proteins of other fungi, suggesting that they arose late in the evolution of fungi associated with the specialization of ChAPs as cargo adaptors.

Monitoring Chitin Deposition During Septum Assembly in Budding Yeast

The synthesis of the septum is a critical step during cytokinesis in the fungal cell. Moreover, in Saccharomyces cerevisiae septum assembly depends mostly on the proper synthesis and deposition of chitin and, accordingly, on the timely regulation of chitin synthases. In this chapter, we will see how to follow chitin synthesis by two complementary approaches: monitoring chitin deposition in vivo at the septum by calcofluor staining and fluorescence microscopy, and measuring the chitin synthase activities responsible for this synthesis.

Architecture and biosynthesis of the Saccharomyces cerevisiae cell wall

The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.

Chitin synthases with a myosin motor-like domain control the resistance of Aspergillus fumigatus to echinocandins

Aspergillus fumigatus has two chitin synthases (CSMA and CSMB) with a myosin motor-like domain (MMD) arranged in a head-to-head configuration. To understand the function of these chitin synthases, single and double csm mutant strains were constructed and analyzed. Although there was a slight reduction in mycelial growth of the mutants, the total chitin synthase activity and the cell wall chitin content were similar in the mycelium of all of the mutants and the parental strain. In the conidia, chitin content in the ΔcsmA strain cell wall was less than half the amount found in the parental strain. In contrast, the ΔcsmB mutant strain and, unexpectedly, the ΔcsmA/ΔcsmB mutant strain did not show any modification of chitin content in their conidial cell walls. In contrast to the hydrophobic conidia of the parental strain, conidia of all of the csm mutants were hydrophilic due to the presence of an amorphous material covering the hydrophobic surface-rodlet layer. The deletion of CSM genes also resulted in an increased susceptibility of resting and germinating conidia to echinocandins. These results show that the deletion of the CSMA and CSMB genes induced a significant disorganization of the cell wall structure, even though they contribute only weakly to the overall cell wall chitin synthesis.