Research on antizyme (AZ) in fungi has focused on the mechanism by which AZ inhibits ornithine decarboxylase (ODC). Moreover, there are existing reports on the regulation of AZ protein translation by TOR.
Background: There is an urgent need to search for new and economical ways to utilize diverse lignocellulose. Ganoderma lucidum is well-known edible medicinal fungus that has a strong ability to degrade a wide variety of cellulosic biomass and its nutrient utilization is closely related to extracellular cellulase. Nicotinamide adenine dinucleotide (NAD+), a nutritional sensor molecule, can respond to nutritional states and regulate cellular metabolism. Nicotinamide mononucleotide adenyltransferase (nmnat) is the key enzyme that catalyses the biosynthesis of NAD+.Result: In this study, a homologue of the gene encoding nmnat was cloned from G. lucidum. The Agrobacterium tumefaciens -mediated transformation (ATMT) method was used to construct the two overexpression strains OE:: nmnat4 and OE:: nmnat19 in G. lucidum. In the overexpression strains, the transcript levels of the nmnat gene and the NAD+ content were significantly increased. Gl nmnat overexpression strains showed dramatically stronger colony growth on different carbon sources, and the intracellular Ca 2+ concentration increased 3.95-fold and 2.10-fold in OE:: nmnat4 and OE:: nmnat19 , respectively, compared with WT strains. The CMCase activity increased by approximately 2.8-fold and 3-fold, and p NPGase activity increased by approximately 1.9-fold and 2.1-fold in OE:: nmnat4 and OE:: nmnat19 strains compared with the WT strains, respectively. Furthermore, it was found that NAD+ might induce cellulase production by regulating cytosolic Ca 2+ concentration.Conclusions: Taken together, our results revealed for the first time that NAD + could stimulate cellulase production and demonstrated that NAD + could increase the transcript levels of cellulase genes via the intracellular Ca 2+ concentration in G. lucidum. This research also provides a theoretical basis for conducting cellulase-related work on other basidiomycetes.
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