senescent: A New Neurospora crassa Nuclear Gene Mutant Derived from Nature Exhibits Mitochondrial Abnormalities and a “Death” Phenotype

Navaraj, Arunasalam and Pandit, Alka and Maheshwari, Ramesh (2000) senescent: A New Neurospora crassa Nuclear Gene Mutant Derived from Nature Exhibits Mitochondrial Abnormalities and a “Death” Phenotype. In: Fungal Genetics and Biology, 29 (3). pp. 165-173.

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Abstract

Navaraj, A., Pandit, A., and Maheshwari, R. 2000. senescent: A new Neurospora crassa nuclear gene mutant derived from nature exhibits mitochondrial abnormalities and a “death” phenotype. Fungi are capable of potentially unlimited growth. We resolved nuclear types from multinuclear mycelium of a phenotypically normal wild isolate of the fungus Neurospora intermedia by plating its uninucleate microconidia and obtained a strain which, unlike the “parent” strain, exhibited clonal senescence in subcultures. The mutant gene, senescent, was introgressed into N. crassa and mapped four map units to the right of the his-1 locus on linkage group VR. senescent is the first nuclear gene mutant of Neurospora derived from nature that shows the death phenotype. Death of the sen mutant occurred faster at $34^o C$ than at 22 or $26^o C$. Measurements of oxygen uptake of conidia using respiratory inhibitors and the spectrophotometric analyses of mitochondrial cytochromes showed that in sen cultures grown at $34^o C$, cytochromes b and $aa_3$ were present but cytochrome c was absent. By contrast at $26^o C$, cytochromes b and c were present but cytochrome $aa_3$ was diminished in the late subcultures. This suggested that the sen mutation does not affect the potential to produce functional cytochromes. The deficiency of the respiratory chain cytochromes may not be the cause of death of the sen mutant because the cytochrome c and $aa_3$ mutants of N. crassa are capable of sustained growth whereas sen is not. Possible explanations for the observations are discussed.

Item Type:	Journal Article
Publication:	Fungal Genetics and Biology
Publisher:	Academic Press
Additional Information:	Copyright of this article belongs to Academic Press.
Keywords:	Senescence;Fungus;N.crassa;Nuclear gene;Mutant;Mitochondria
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	09 Oct 2007
Last Modified:	19 Sep 2010 04:40
URI:	http://eprints.iisc.ac.in/id/eprint/12112

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