Development of chloroplast engineering tools for Asterarcys sp.: A resilient scenedesmaceae microalga

Abstract

The vast biodiversity of algae presents an opportunity to discover novel microalgae with diverse phenotypes having a commercial application. Asterarcys sp. is a resilient microalga demonstrating tolerance to elevated light intensity and nitric oxide concentrations with simultaneous production of high biomass and lipid content. The development of genetic tools for this microalga will further widen its biotechnological potential. We report the construction of a modular chloroplast vector as well as the establishment of a chloroplast transformation method for this microalga using the endogenous genetic sequences. The endogenous promoters, located upstream of psbA and atpA genes were isolated using the recently published chloroplast genome and were functionally validated in E. coli. Similarly, the homology arms of the vector were isolated by genome walking from the rrnS-rrnL operon using the chloroplast genome sequence of Asterarcys sp. These genetic elements were assembled to construct a species-specific vector with codon optimized aadA gene as the selectable marker. To the best of our knowledge, this is the first report of chloroplast engineering of a microalga belonging to the Scenedesmaceae.