The cellulose synthase gene of Dictyostelium

Abstract

Cellulose is a major component of the extracellular matrices formed during development of the social amoeba, Dictyostelium discoideum. We isolated insertional mutants that failed to accumulate cellulose and had no cellulose synthase activity at any stage of development. Development proceeded normally in the null mutants up to the beginning of stalk formation, at which point the culminating structures collapsed onto themselves, then proceeded to attempt culmination again. No spores or stalk cells were ever made in the mutants, with all cells eventually lysing. The predicted product of the disrupted gene (dcsA) showed significant similarity to the catalytic subunit of cellulose synthases found in bacteria. Enzyme activity and normal development were recovered in strains transformed with a construct expressing the intact dcsA gene. Growing amoebae carrying the construct accumulated the protein product of dcsA, but did not make cellulose until they had developed for at least 10 hr. These studies show directly that the product of dcsA is necessary, but not sufficient, for synthesis of cellulose.

The Inositol 1,4,5-Trisphosphate Receptor Is Required to Signal Autophagic Cell Death

“…Altogether, in 14 of 14 experiments checking vacuolization by phase-contrast microscopy there was marked DIF-induced vacuolization of control DH1 cells, and in 12 of these 14 experiments there was no detectable vacuolization of DH1.iplA Ϫ cells. Whereas in the presence of DIF DH1 cells synthesized cellulose shells, reflecting the induction of the cellulose synthesis machinery (Blanton et al, 2000), DH1.iplA Ϫ (ins) cells did not ( Figure 2B), suggesting that iplA may act upstream of this induction.…”

Progress and perspectives in signal transduction, actin dynamics, and movement at the cell and tissue level: lessons fromDictyostelium

“…Some of the key prestalk specific expressed genes code for components of the extracellular matrix, which is a complex composite of proteins and cellulose [109,110]. Cells taken from slugs are not able to move on a glass substrate any more while pre-and aggregation stage cells can.…”

The Dictyostelium discoideum cellulose synthase: Structure/function analysis and identification of interacting proteins

“…The initial characterization of dcsA was performed in collaboration with Dr. William F. Loomis (University of California-San Diego; Blanton et al, 2000). This work began prior to the start of the project period (indeed, our preliminary results figured prominently in the proposal), but continued well into the first year of the project, Dr. Loomis's lab isolated dcsA as part of a large NIH-funded project (the D i c t y o s t e l i u m Developmental Gene Program; http://glamdring.ucsd.edu/others/dsmith/dictydb.html) using restriction-enzyme mediated insertional mutagenesis (REMI; Kuspa and Loomis, 1992) to identify important developmentally regulated genes (Loomis et al, 1994).…”

“…The major accomplishments of this project were: (1) the initial characterization of dcsA, the gene for the putative catalytic subunit of cellulose synthase in the cellular slime mold Dictyostelium discoideum (Blanton et al, 2000); (2) the detection of a developmentally regulated event (unidentified, but perhaps a protein modification or association with a protein partner) that is required for cellulose synthase activity (i.e., the dcsA product is necessary, but not sufficient for cellulose synthesis) (Blanton et al, 2000); (3) the continued exploration of the developmental context of cellulose synthesis and DcsA (Zhang et al, 2001;Levraud et al, 2003); (4) the isolation of a GFP-DcsA-expressing strain (work in progress); and (5) the identification of Dictyostelium homologues for plant genes whose products play roles in cellulose biosynthesis (work in progress). Although our progress was slow and many of our results negative, we did develop a number of promising avenues of investigation that can serve as the foundation for future projects.…”

“…In fact, the expression pattern of Actin15 is constitutive from amoebae through aggregation, but then tapers off significantly during later development (Cohen et al, 1986). In contrast, dcsA is not expressed in amoebae and reaches a peak during mid-to late development (Blanton et al, 2000). RNA blots of extracts from TL128 showed a constant level of dcsA mRNA throughout all stages of development (including amoebae; Blanton et al, 2000).…”