Sorbose transport in Neurospora crassa.
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Biomedical subjects
Publications and source records attributed to E L Tatum.
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The distribution and localization of structural polymers in the cell wall of Neurospora crassa has been studied by selective removal and light and electron microscope examination. Observations with the light microscope indicated that each polymer by itself can provide structural integrity to the cell wall. Examination by electron microscopy showed that the cell wall consists of an outer layer of thick fibrils, identified chemically as a glucan-peptide-galactosamine complex, and an inner layer made up of beta-1,3 glucan and thin fibrils of chitin.
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Two morphologically distinctive slow growing strains of Neurospora crassa have been isolated and studied. These, abn-1 and abn-2, differ from wild type in that their growth rates are greatly reduced and often irregular, aerial hyphae are absent, conidia are extremely rare, and no protoperithecia are formed. Growth was not improved by addition of any nutrients tested, oxygen consumption was similar to that of wild type, and cytochrome c appeared abnormally high, and b low or absent. Both abn strains gave rise only to normal progeny in crosses with normal strains. The abn characteristics appear in heterocaryons, and have been transmitted to other genetic strains by means of heterocaryosis followed by plating of conidia. Conidia formed by such heterocaryons typically showed low viability, and gave rise to cultures with great variability in growth rate, morphology, and survival. Even apparently normal derived cultures often later became abnormal or died. It is concluded that the abnormal characteristics are determined primarily by cytoplasmic factors. This conclusion was strengthened by the transmission of the typical characteristics to normal strains by microinjection of cytoplasm from abn cultures, even without demonstrable transfer of nuclei. This constitutes the first time microinjection techniques have been successfully applied to the analysis of a cytoplasmic character in Neurospora.
Nuclear fractions isolated from mutants of Neurospora produced no effect when microinjected into mutants with complementary biochemical requirements. DNA isolated from the nuclear fractions similarly injected also had no effect. Mitochondrial fractions isolated from an abnormal inositolless strain (abn-1) produced drastic changes in the rate of growth, morphology, reproductive characteristics, and cytochrome spectra of normal inositolless strains when single hyphal compartments were microinjected and isolated, whereas the mitochondrial fractions of the wild type produced no effect. These results provide evidence for the transmission of biochemical and biological characters when mitochondria are transferred to new nucleocytoplasmic environments.
Mahadevan, P. R. (The Rockefeller Institute, New York, N.Y.), and E. L. Tatum. Relationship of the major constituents of the Neurospora crassa cell wall to wild-type and colonial morphology. J. Bacteriol. 90:1073-1081. 1965.-The relationship of cell wall to morphology in Neurospora crassa was studied by correlating the levels of structural polymers of the cell wall with wild-type and colonial morphology. The cell wall of N. crassa contains at least four major complexes: a peptide-polysaccharide complex; two glucose polymers, one of which was found to be a laminarinlike beta-1,3-glucan; and, lastly, chitin. The levels of one or more of these structural polymers are consistently altered in single-gene mutants with colonial growth, and in sorbose-induced colonial growth. The proportions of these polymers, particularly of the peptide-polysaccharide complex and the beta-1,3-glucan, appear to be important to morphology.
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