Transformation of Aspergillus nidulans by RNA from rat macrophages stimulated with lipopolysaccharide

Exogenous RNA molecules can be incorporated into eukaryotic cells and can exert a variety of biological effects. We have previously described a model system for correcting genetic alterations of an Aspergillus nidulans mutant using homologous RNA and this phenomenon was named retrotransformation. In the present study, the retrotransformation of A. nidulans was performed with heterologous RNA which was extracted from rat macrophages stimulated with lipopolysaccharide (LPS). Protoplasts of A. nidulans were treated with this mammalian RNA and retrotransformants were detected by their ability to secrete the neutrophil recruitment inhibitory factor (NRIF) which is released by LPS-stimulated macrophages. Twenty two retrotransformant colonies were analyzed and only two retrotransformants, named RT1 and RT2, were able to secrete NRIF. The occurrence of sectors (RT1.1, RT2.1 and RT2.2) in retrotransformants RT1 and RT2 is due to mitotic instability which can be accompanied by loss of genomic extra-segments. The three sectors detected did not exhibit NRIF activity possibly due to loss of the NRIF gene present in the genome of retrotransformants RT1 and RT2. The NRIF like material secreted by RT2 shows the same lectin property and biological activity of NRIF released by LPS-stimulated macrophages. To date, this work is the first example of retrotransformation described in lower eukaryotes with heterologous RNA.