Although much progress has been made in the study of cell wall biosynthetic genes in the model filamentous fungus Aspergillus nidulans, there are still targets awaiting characterization. An example is the gene celA (ANIA_08444) encoding a putative mixed linkage glucan synthase. To characterize the role of celA, we deleted it in A. nidulans, analyzed the phenotype of the mycelium and performed RNA-Seq. The strain shows a very strong phenotype, namely "balloons" along the hyphae and aberrant conidiophores, as well as an altered susceptibility to cell wall drugs. These data suggest a potential role of the gene in cell wall-related processes. The Gene Ontology term Enrichment analysis shows increased expression of secondary metabolite biosynthetic genes (sterigmatocystin in particular) in the deleted strain. Our results show that the deletion of celA triggers a strong phenotype reminiscent of cell wall-related aberrations and the upregulation of some secondary metabolite gene clusters in A. nidulans.