Several Aspergillus species are well-known for the production of a variety of 
organic acids. In this study, a cloned based transcriptomics approach was used 
to identify genes crucial in the biosynthesis pathway for one of these acids, 
itaconic acid. From a number of different Aspergillus terreus controlled batch 
fermentations, those cultures with the largest difference in itaconic acid titer 
and productivity were selected for mRNA isolation. cDNAs derived from these mRNA 
samples were used for subsequent hybridization of glass slide arrays based on a 
collection of 5000 cDNA clones. A selection of 13 cDNA clones resulting in the 
strongest (>10-fold) differential hybridization signals were identified and 
subsequently the inserts of these clones were sequenced. Sequence analysis 
revealed the presence of in total five different gene inserts among the 
sequenced clones. From one of these sequences, encoding a gene of the MmgE-PrpD 
family, the full length coding region was shown to encode one of the crucial 
itaconic acid pathway enzymes cis-aconitate decarboxylase, by heterologous 
expression in Escherichia coli. Expression of this gene in Aspergillus niger, 
which is a natural citric acid producer, resulted in itaconate production. 
Genome analysis suggests that in A. terreus the cis-aconitate decarboxylase gene 
is part of an itaconate acid related gene cluster including genes encoding two 
pathway specific transporters and a Zinc finger protein. Interestingly, this 
cluster is directly linked to the large lovastatin gene cluster.