THE ISOLATION AND CHARACTERIZATION OF MUTANTS DEFECTIVE IN NITRATE ASSIMILATION IN NEUROSPORA CRASSA

Abstract

The isolation and characterization of mutants altered for nitrate assimilation in Neurospora crassa is described, The mutants isolated can be subdivided into five classes on the basis of growth tests that correspond to the growth patterns of existing mutants at six distinct loci. Mutants with growth characteristics like those of nit-2, nit-3 and nit-6 are assigned to those loci on the basis of noncomplementation and lack of recombination. Mutants that, from their growth patterns, appear to lack the molybdenum-containing cofactor for both nitrate reductase and xanthine dehydrogenase subdivide into three loci (nit-7, nit4 and nit-9), all of which are genetically distinct from nit-1. nit-9 is a complex locus consisting of three complementation groups and thus appears similar to the cnxABC locus of Asperillus nidulans. Extensive complementational and recombinational analyses reveal that nit-4 and nit-5 are alleles of the same locus, and two new alleles of that locus have been isolated. The results indicate that, as in A. nidulans, nitrate assimilation in N. crassa requires at least four loci (nit-1,7,8 and 9) to produce the molybdenum co-factor for nitrate reductase (and xanthine dehydrogenase), one locus (nit-3) to code for the nitrate reductase apoprotein, one locus (nit-6) to code for the nitrite reductase approtein and only one locus (nit-4/5) for the regulation of induction of the pathway by nitrate and nitrite.

A Chemically Defined Medium That Supports Mycotoxin Production by Stachybotrys chartarum Enabled Analysis of the Impact of Nitrogen and Carbon Sources on the Biosynthesis of Macrocyclic Trichothecenes and Stachybotrylactam

“…NO 3 − has to be reduced to the level of NH 4 + before it can feed into metabolism, a process that requires genes that encode nitrate and nitrite reductases ( 64 ). Such genes are well defined in other fungi, for example, Neurospora crassa ( Sordariales , Ascomycota ) ( 65 ) and Aspergillus nidulans ( Eurotiales , Ascomycota ) ( 66 ), but are not yet identified in the genome of S. chartarum .…”

The History of the Molybdenum Cofactor—A Personal View

“…It is reasonable to assume that the multitude of mutant loci in each model organism are involved in Moco metabolism; a first and easy experimental step was to grow the different NR-deficient mutants on a high-molybdate medium (1 mM): among the Aspergillus nidulans Cnx mutants, one locus turned out to be partially molybdate-repairable [ 63 ]; in the plant Nicotiana tabacum ; one mutant type was also partially molybdate-repairable [ 40 ]. Among newly described Neurospora crassa nit loci [ 64 ], again, mutants in one locus were molybdate-repairable [ 40 ]. Additionally, among the E. coli chl mutants, two groups were molybdate-repairable, although the situation is more complex (see below).…”

Transzformációs és további molekuláris módszerek alkalmazása az Ampelomyces hiperparazita gombák biológiájának tanulmányozására

“…Minimál táptalajon minden esetben, és a KO transzformánsok esetén a nitrát tartalmú táptalajon is gyenge növekedés, vékony telepek és gyenge sporuláció volt tapasztalható. Ez a morfológia tipikusan a nitráthiány ("nitrátéhség") táptalajon való megnyilvánulása(Tomsett & Garrett 1980, Espeso és mtsai 2019. A PCR-alapú genotipizálás és a táptalajos tesztek eredményei egyaránt bizonyítják, hogy sikeresen megvalósult a célzott génkiütés az Ampelomyces-transzformánsokban.Az előbb ismertetett jellemzők alapján kijelenthetjük, hogy az élesztő rekombinációs klónozással való plazmid előállítás és az azt követő Agrobacterium-közvetítette transzformálás együttesen lehetségessé teszik az Ampelomyces-törzsek funkcionális genetikai vizsgálatainak megindítását.…”