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URL: https://dx.doi.org/10.17504/protocols.io.sh3eb8n

Authors: Fatma Gomaa, Zuhong Li, Roberto Docampo, Peter Girguis, Virginia Edgcomb

Group: Protist Research to Optimize Tools in Genetics (PROT-G)

Summary: B. saltans cells were electroporated using a square-wave electroporator (Nepa21, Bulldog Bio, Inc.) using one poring pulse of 200 volts with a pulse duration of 25 ms and five transfer pulses of 60 volts with a pulse duration of 99 ms, with plasmid targeting the 18S region (18S-GFP). A schematic representation of the plasmid, the target locus and the expected site of integration into the B. saltans genome is shown in Figure 1. Electroporated cells were selected with 1 µg/ml of G418, added 24 hours after electroporation. Cells were washed and subcultured into fresh selection medium every 3-4 days. G418 resistant cells started to emerge 7-9 days post-electroporation. Cells were processed for genotyping analysis to confirm plasmid integration 3 weeks post-electroporation. DNA was extracted from pools of transfected and wild cells using the Qiagen DNeasy Blood & Tissue kit. PCR analyses were used to characterize the 18S-GFP tagging using 6 sets of PCR primers, as shown in Figure 1 C. Gel electrophoresis image (Figure 2) showing the amplified PCR products at the expected sizes. Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)Electroporated cells were selected with 1 µg/ml of G418, added 24 hours after electroporation. Cells were washed and subcultured into fresh selection medium every 3-4 days. G418 resistant cells started to emerge 7-9 days post-electroporation. Cells were processed for genotyping analysis to confirm plasmid integration 3 weeks post-electroporation. DNA was extracted from pools of transfected and wild cells using the Qiagen DNeasy Blood & Tissue kit. PCR analyses were used to characterize the 18S-GFP tagging using 6 sets of PCR primers, as shown in Figure 1 C. Gel electrophoresis image (Figure 2) showing the amplified PCR products at the expected sizes. Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)Cells were processed for genotyping analysis to confirm plasmid integration 3 weeks post-electroporation. DNA was extracted from pools of transfected and wild cells using the Qiagen DNeasy Blood & Tissue kit. PCR analyses were used to characterize the 18S-GFP tagging using 6 sets of PCR primers, as shown in Figure 1 C. Gel electrophoresis image (Figure 2) showing the amplified PCR products at the expected sizes. Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)PCR analyses were used to characterize the 18S-GFP tagging using 6 sets of PCR primers, as shown in Figure 1 C. Gel electrophoresis image (Figure 2) showing the amplified PCR products at the expected sizes. Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)Gel electrophoresis image (Figure 2) showing the amplified PCR products at the expected sizes. Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)Amplified PCR#1 with primer sets Ribo_tag_forward & GFP reverse (800 bp)Amplified PCR #2 with primer sets Neo_forward & Ribo_tag_reverse (1000 bp)Amplified PCR #3 with primer sets TubR & IG forward ( 3 bands)Amplified PCR #4 with primer sets Tub_forward & IG reverse (3 bands)Amplified PCR #5 with primer sets Ribo_tag_forward & Ribo_tag_reverse (Wild (C) cells band at 350 bp, transfected cells S1 and S2 two bands, 350 bp and 2800 bp)Figure 1: Schematic representation of the (A); the 18S- GFP plasmid; (B) Ribosomal operon in B. saltans genome (C); and the expected site of plasmid integration in B. saltans genome through homologous regions 1 and 2 (HR1, HR2).Figure 2: Agarose gel electrophoresis image of the amplified PCR products for B. saltans cells transfected with 18S-GFP Cassette (S1 and S2) and the wild type cells (C). The primers sets and the expected product sizes are mentioned above in the text.Figure 3: B. saltans cells transfected with 18S-GFP tagging cassette. On the left: a light microscopy image showing the B. saltans cells (around 4 cells at different level). On the right: GFP fluorescent signal detected in the transfected cell. Scale bar 10 μm.

Affiliations: Harvard University, University of Georgia, University of Georgia, Harvard University, Woods Hole Oceanographic Institution

Version: 1

Publication Date: 2018

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