A core tenet of synthetic biology is that well-characterized regulatory elements are essential for engineering biological systems. Here, we characterize the specificity and expression levels of 18 short (254 to 880 bp) candidate germline promoters using a single-copy gfp reporter assay in C. elegans . Six promoters resulted in ubiquitous expression, three did not drive detectable expression, and nine were germline-specific. Several promoters drove stronger germline expression than the commonly-used mex-5 promoter. The promoters range across expression levels and facilitate, for example, low expression of toxic transgenes or high expression of gene editing enzymes, and their compactness facilitates gene synthesis.
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