Identification and Functional Analysis of the psaD Promoter of Chlorella vulgaris Using Heterologous Model Strains.

<italic>Chlorella</italic> has great potential as a bio-factory for production of value-added compounds. To produce the desired chemicals more efficiently in <italic>Chlorella</italic>, genetic tools for modification of <italic>Chlorella</italic> need to be developed, especially an endogenous promoter. In this study, the promoter of photosystem I protein D (<italic>psaD</italic>) from <italic>Chlorella vulgaris</italic> UTEX395 was identified. Computational analysis revealed the presence of several putative cis-acting elements, including a potential core element, and light-responsive or stress-responsive elements. Gene expression analysis in heterologous expression system in <italic>Chlamydomonas</italic><italic>reinhardtii</italic> and <italic>Nicotiana</italic><italic>benthamiana</italic> showed that <italic>CvpsaD</italic> promoter can be used to drive the expression of genes. Functional analysis of this promoter suggested that the initiator element (Inr) is important for its function (i.e., TATA-less promoter) and that an additional factor (e.g., downstream of the transcriptional start site) might be needed for light response. We have shown that the <italic>CvpsaD</italic> promoter is functional, but not sufficiently strong, both in microalgae and higher plant. [ABSTRACT FROM AUTHOR]