Nourseothricin as a novel drug for selection of transgenic Giardia lamblia

TL;DR

This paper introduces Nourseothricin as a new drug to help study the parasite Giardia lamblia by enabling genetic modifications.

Contribution

The novel contribution is the identification of Nourseothricin as a reliable selection marker for transgenic Giardia lamblia.

Findings

Giardia cells are sensitive to Nourseothricin.

Expression of SAT-1 gene confers resistance to Nourseothricin.

Nourseothricin resistance can be used in combination with Neomycin and Puromycin for dual transfection selection.

Abstract

Functional gene and protein characterizations in parasitic protists are often limited by their genetic tractability. Despite the development of CRISPR-Cas9-derived or inspired approaches for a handful of protist parasites, the overall genetic tractability of these organisms remains limited. The intestinal parasite Giardia lamblia is one such species, with the added challenge of a paucity of reliable selection markers.

To address this limitation, we tested the feasibility of using Nourseothricin as an effective selection agent in Giardia. Here, we report that axenically-grown WB Giardia cells are sensitive to Nourseothricin and that engineering expression of the streptothricin acetyltransferase (SAT-1) gene from Streptomyces rochei in transgenic parasites confers resistance to this antibiotic. Furthermore, we determine that SAT-1-expressing parasites are cross-resistant neither to Neomycin nor Puromycin, which are widely used to select for transgenic parasites. Consequently, we show that Nourseothricin can be used in sequential combination with both Neomycin and Puromycin to select for dual transfection events.

This work increases the number of reliable selection agents and markers for Giardia genetic manipulation, expanding the limited molecular toolbox for this species of global medical importance.

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