Fig. 1

Identification and characterization of aicda transcript(s) in Atlantic cod. A Amplification of full-length AID mRNA(s) through RACE-PCR using 1 µg of splenic RNA. B Analyses of the RACE-PCR sequencing data revealed two mRNA transcripts encoding a full-length aicda and a truncated isoform. C The ATGpr website was used to identify the initiation codon, coding sequence (CDS), and the stop codon with highest probability. The Kozak sequence, CDS, stop codon, poly-A signal, and poly-A tail are labelled for each identified mRNA sequence. Comparison of the Gm-aicda genomic region and identified transcripts showed different transcription start site utilization among the two transcripts resulting in the absence of the first exon in the truncated transcript (T-Gm-aicda). D Confirmation of the presence of both aicda transcripts in Atlantic cod individuals through RT-PCR. One microgram of splenic total RNA of each pIC-stimulated fish sampled at 24 HPI was used for cDNA synthesis. Eleven individual fish were included. Isoform-specific primers (ISPs) and 2.5 µl of diluted cDNA (equivalent to 25 ng of initial RNA) were used to amplify both transcripts. The amplicons were sequenced to confirm the results