This paper presents the results of research carried out in a Biology teacher education program at a Brazilian public university, during the performance of supervised internship in high schools. From the epistemic framework of Discourse Analysis with a French strand, the discursive positions (of teacher and student) were analyzed in the mediation promoted by trainee undergraduates when using their authorial texts in Biology classes. Our data sources were the teaching projects containing authorial texts, a field journal, and classes’ video records. The results demonstrate that when considering the subject positions (author and reader), the trainees involved students in the activity of mediation and reading comics, structuring their practices within a controversial approach to the pedagogical discourse. Finally, we indicate to the research area the relevance of a discursive basis in studies on the role of reading and language in Science Education and, above all, to insert it as a relevant topic to be discussed.