Biochemical genetics of Neurospora crassa conidial germination.

Abstract

INTRODUCTION ....................... ..................................... 2 THE THREE PHASES OF THE ASEXUAL LIFE CYCLE OF NEUROSPORA CRASSA ............................................................... 2 Conidial Germination ...................... ................................. 2 Vegetative Growth.......................................................... 2 Conidiation ................3................................................3 CONIDIA ARE DORMANT SPORES ................... ...................... 4 COMPARISON OF THE STRUCTURE AND COMPOSITION OF CONIDIA AND MYCELIA ........................................................... 5 Ultrastructure ........................................................... 5 Cell Wall ........................................................... 5 Lipids ........................................................... 6 Protein ........................................................... 6 Nucleic Acids ........................................................... 6 DNA and Chromatin .................................................... 6 RNA ................................................................ 7 Low-Molecular-Weight Compounds ................... ....................... 7 Exocellular Enzymes .................................................... 8 CONIDIAL GERMINATION .................................................. 9 BIOCHEMICAL CHANGES THAT OCCUR DURING CONIDIAL GERMINATION 11 Metabolic Intermediates .................................................... 12 Endogenous Amino Acid Pools ............................................. 12 Pyridine Nucleotides .................................................... 13 Glutathione Thiol-Disulfide Status ................. ........................ 13 Macromolecules ..................................................... ........ 13 Protein Synthesis and Polysome Assembly ........... ....................... 13 RNA Synthesis ..................................................... 14 DNA Synthesis and Nuclear Division .............. ......................... 15 Cell Wall Polymers ..................................................... 15 Specific Activity of Enzymes ................................................ 16 Molecular Transport .................................................... 19 Electron Transport and Oxidative Phosphorylation ........ .................. 20 GENETIC ANALYSIS OF CONIDIAL GERMINATION ....... ................. 20 Methods for Characterization of Mutants ............. ........................ 21 Spot Test, Microscopy Observation of Germ Tube Formation ...... .......... 21 Colony Formation, Plating Efficiency .............. ........................ 21 Growth of Individual Conidia in Liquid Media ......... ..................... 21 Germination in Shake Cultures............................................ 21 Selection of Mutants .................................................... 22 Heterocaryon Analysis .................................................... 22 Mutations that Affect Germination .................... ....................... 23 Phase-Specific Mutations .................................................... 24 Conclusions ..................... ................................ 24 CLASSIFICATION OF EVENTS IN GERMINATION ........ ................... 24 BREAKING OF DORMANCY ................................................. 26 Proposed Model for the Germination of Neurospora Conidia ....... ............. 26 Dormancy and Oxidized Sulfhydryls ........... ............................ 26 Germination and the Reduction of Disulfide Bonds ....... .................. 27 Initial Requirements for NADH and NADPH ......... ...................... 27 Endogenous Source for the Generation of NADH and NADPH ...... ......... 27 Possible Relationships to the Germination of Other Organisms ...... .......... 28 MOLECULAR CONTROL OF DEVELOPMENT ......... ...................... 30 Interpretation of Experimental Observations ............................. ;... 31 Proposed Experiments .................................................... 32 SUMMARY............................................................ 33 LITERATURE CITED .................................................... 33