Fig. 4

Tandem Zmat2 genes in the opossum genome. a. Diagram of the opossum Zmat2 locus on chromosome 1, showing two Zmat2 genes, termed here Zmat2–1 and Zmat2–2, and their divergent transcriptional orientations. Exons are depicted as boxes, red for Zmat2–1 and black for Zmat2–2, with coding segments solid, and noncoding regions white. b. Mapping the beginning and end of opossum Zmat2–1 and 2–2: diagram of exon 1 (left) and exon 6 (right), and graphs of gene expression data from the SRA NCBI RNA-sequencing library, SRX3040092 (Additional file 1: Table S1), using 60 base pair genomic segments a-e, and a-f, respectively, as probes. Shown below the right graph is the DNA sequence of the putative 3′ end of exon 6. A potential polyadenylation signal (AATAAT) is underlined and a vertical arrow denotes the possible 3′ end of Zmat2 transcripts. c. Gene expression data from SRX3040092 for each opossum Zmat2 gene, using probes for exons 1 + 2, and exon 6 (Additional file 2: Table S2) that discriminate between transcripts from Zmat2–1 and Zmat2–2. d. Diagram of opossum Zmat2 transcripts. Both genes produce mRNAs that are identical in length, and are 99.9% identical in DNA sequence. The coding segment is in black and non-coding regions are in white. The length is in nucleotides and the number of codons in the open reading frame are listed. e. Diagram of opossum ZMAT2 proteins, with NH₂ (N) and COOH (C) terminal (term), and zinc finger (ZnF) regions labeled and color-coded. The signal amino acid substitution at position 128 is labeled (V in ZMAT2–1, and M in ZMAT2–2