Establishing the green algae as a platform for recombinant protein production.

, a genetically close relative of the model green alga , shows significant potential as a host for recombinant protein expression. Because of the close genetic relationship between and , this species offers an additional reference point for advancing our understanding of photosynthetic organisms, and also provides a potential new candidate for biotechnological applications. This study investigates C. incerta's capacity to express three recombinant proteins: the fluorescent protein mCherry, the hemicellulose-degrading enzyme xylanase, and the plastic-degrading enzyme PHL7. We have also examined the capacity to target protein expression to various cellular compartments in this alga, including the cytosol, secretory pathway, cytoplasmic membrane, and cell wall. When compared directly with , exhibited a distinct but notable capacity for recombinant protein production. Cellular transformation with a vector encoding mCherry revealed that produced approximately 3.5 times higher fluorescence levels and a 3.7-fold increase in immunoblot intensity compared to . For xylanase expression and secretion, both and showed similar secretion capacities and enzymatic activities, with comparable xylan degradation rates, highlighting the industrial applicability of xylanase expression in microalgae. Finally, showed comparable PHL7 activity levels to , as demonstrated by the in vitro degradation of a polyester polyurethane suspension, Impranil DLN. Finally, we also explored the potential of cellular fusion for the generation of genetic hybrids between and as a means to enhance phenotypic diversity and augment genetic variation. We were able to generate genetic fusion that could exchange both the recombinant protein genes, as well as associated selectable marker genes into recombinant offspring. These findings emphasize 's potential as a robust platform for recombinant protein production, and as a powerful tool for gaining a better understanding of microalgal biology.