Expression of the arylsulfatase gene from the beta 2-tubulin promoter in Chlamydomonas reinhardtii.

Arylsulfatase, produced by Chlamydomonas reinhardtii during sulfur-limited growth, is secreted into the periplasmic space and is readily assayed using a chromogenic substrate. To assess the usefulness of the gene encoding arylsulfatase (ars) as a reporter gene in C. reinhardtii, we have fused the promoter region of the beta 2-tubulin gene (tubB2) to the coding region of an ars genomic clone to form a tubB2/ars chimeric sequence. This construct was introduced into C. reinhardtii, strain CC425 (cw-15, arg-2), via cotransformation with the argininosuccinate lyase gene (which complements the arg-2 lesion) (1). Transformants expressing arylsulfatase (Ars) in sulfur-sufficient medium were isolated and subsequently shown to contain the tubB2/ars gene. RNA analysis determined that tubB2/ars transcripts accumulated in these cells. Abundance of the chimeric transcript increased immediately following deflagellation in a manner similar to that of the endogenous tubB2 transcript. Thus, chimeric genes incorporating ars coding sequences and heterologous promoters can be used to examine regulated gene expression in C. reinhardtii.