Regions of the Didymium iridis mitochondrial genome were identified with similarity to typical mitochondrial genes; however, these regions contained numerous stop codons. We used RT-PCR and DNA sequencing to determine whether, through RNA editing, these regions were transcribed into mRNAs that could encode functional proteins. Ten putative gene regions were examined: atp1, atp6, atp8, atp9, cox1, cox2, cyt b, nad4L, nad6, and nad7. The cDNA sequences of each gene could encode a functional mitochondrial protein that was highly conserved compared with homologous genes. The type of editing events and editing sequence features were very similar to those observed in the homologous genes of Physarum polycephalum, though the actual editing locations showed a variable degree of conservation. Edited sites were compared with encoded sites in D. iridis and P. polycephalum for all 10 genes. Edited sequence for a portion of the cox1 gene was available for six myxomycetes, which, when compared, showed a high degree of conservation at the protein level. Different types of editing events showed varying degrees of site conservation with C-to-U base changes being the least conserved. Several aspects of single C insertion editing events led to the preferential creation of hydrophobic amino acid codons that may help to minimize adverse effects on the resulting protein structure.

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Homework is an integral component of most science courses but can have an impact on student learning only when students actually complete the assignment. Low completion rate of homework, then, is an impediment to student success in science courses, and a source of frustration for instructor and students alike. Here, we outline a set of design principles supported by research in how students learn, intended to streamline outside-of-class assignments to address course goals, improve student buy-in and motivation, and provide instructors better formative assessment data. We also share examples of outside-of-class assignments aligned to these principles to aid instructors in shortening and focusing the homework they choose to assign in their courses.

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