Title
Molecular expression profile of different cellulolytic enzyme genes in Aspergillus niger in response to UV radiation and chemical mutagenesis
Authors
NASIR MAHMOOD MARIYAH AHSAN ISHFAQ MUHAMMAD SHAHIDA AFZAL ZAFAR QURESHI SYED ALI RAZA NAQVI MUHAMMAD YAR ZULFIQAR ALI KHAN and SOHAIL ANJUM SHAHZAD

Received March 27, 2013
Published Volume 48 Issue 5-6 May-June
Keywords RT-PCR, cellulolytic enzyme genes, Aspergillus niger, mutagenesis

Abstract
Aspergillus niger has several different types of cellulolytic enzyme genes, which are expressed at different levels in response to mutagenesis by UV radiation and chemicals like ethyl methyl sulphonate (EMS). In the present research, the A. niger normal (N) strain was subjected to mutagenesis by UV radiation and EMS. The resultant three strains of A. niger, i.e. chemically mutated (CM), UV mutated (UM) and normal (N), were subjected to biochemical analysis in the first stage of the study and to cellulolytic enzyme gene expression profile analysis in the second stage. Total protein contents were found to be highest (12 mg/mL) in the chemically mutated form of A. niger. As for the enzyme activity, the greatest amylase and pectinase activity was observed in the UV mutated form of the fungus, while the maximum cellulase enzyme activity was observed in the chemically mutated form. This enzyme activity was measured by determining the diameter of the clear zones in plate assays.
For all three strains of A. niger, the comparative expression profiles of cellulolytic enzyme genes CbhB, Exo, eglA, eglB, eglC and eng1 were monitored by reverse transcriptase PCR (RT-PCR) with 0.5% carboxymethyl cellulose (CMC) and 0.3% Avicel in the growth medium. While there was no expression for the Eng1 gene transcript in any of the three strains, Egl-C was found to be expressed predominantly in the A. niger (UM) strain. The remaining transcripts of the cellulolytic enzyme genes were found to be at higher expression levels in A. niger (CM).